MEMBERS OF THE D52 GENE FAMILY

Abstract: The present invention relates to a novel member of the D52 gene family, hD54. The genes and gene fragments of the present invention are themselves useful as DNA and RNA probes for gene mapping by in situ hybridization with chromosomes and for detecting gene expression in human tissues by Northern blot analysis and for the diagnosis and prognosis of breast cancer.

Description: Members of the D52 Gene Family Field of the Invention The present invention relates to genes expressed in breast carcinoma. In particular, the invention relates to a murine homolog and a novel isoform of a human gene expressed in breast carcinoma, and a novel member of the D52 gene family, hD54. Background of the Invention D52 gene family The human D52 (hD52) cDNA was initially cloned during a differential screening of a breast carcinoma cDNA library (Byrne, J.A., et al, Cancer Res. 55:2896-2903 (1995)), and a hD52 cDNA (termed N8) was subsequently identified by differential display of mRNA from normal and tumor-derived lung cell lines (Chen, S-L., et a!., Oncogene 72:741-751 (1996)). The hD52 gene was found to be overexpressed in approximately 40% of breast carcinomas, specifically in the cancer cells (Byrne, J.A., et al, Cancer Res. 55:2896-2903 (1995)). Cloning oϊhD52 orthologues in other species has indicated that D52 proteins may participate in the calcium signaling cascade (Parente (Jr) et al, J. Biol. Chem. 277:20096-20101 (1996)) and the control of cell proliferation (Proux, V., et al, J. Biol. Chem. 277:30790-30797 (1996)). Orthologues of the hD52 gene have been cloned from mouse (Byrne, J. A., et al, Genomics 55:523-532 (1996)), rabbit (Parente (Jr) et al, J. Biol Chem. 277:20096-20101 (1996)), and Japanese quail (Proux, V., et al, J. Biol. Chem. 277:30790-30797 (1996)), and in situ hybridization mapping has indicated that the human and mouse D52 loci are syntenically conserved, having been localized to human chromosome 8q21 (Byrne, J.A., et al, Cancer Res. 55:2896-2903 (1995)), and mouse chromosome 3 Al -3 A2 (Byrne, J. A., etal, Genomics 55:523- 532 (1996)). respectively The rabbit D52 homologue CSPP28 (calcium sensitive phosphoprotein of 28 kDa) was identified as being one of several proteins known to be phosphorylated in response to cholinergic stimulation of gastric parietal cells, and it was postulated that CSPP28 may participate in the calcium signaling cascade in a variety of rabbit tissues (Parente (Jr), J.A., et al, J. Biol Chem. 277:20096- 20101 (1996)). In the Japanese quail (Coturnix coturnix japonica), a D52 homologue RIO was identified as the cellular sequence to which retroviral sequences were joined in chimeric transcripts amplified from in vitro cultures of proliferating neuroretinal cells infected with RAY-1 (Proux, V., et al, J. Biol. Chem. 277:30790-30797 (1996)). Thus, D52 may a represent signaling molecule of a calcium-sensitive signaling pathway mediating or associated with aspects of cellular proliferation. A role for both hD52 and hD53 in, or as markers of cell proliferation was also suggested by the observation that hD52 and hD53 transcript levels were decreased in HL60 and K562 leukemic cell lines, respectively, when these were cultured in the presence of 12-O-tetradecanoylphorbol- 13 -acetate (Byrne, J.A., et al, Genomics 55:523-532 (1996)). While the sequences of D52 proteins are highly conserved between species (Byrne, J.A., et al, Genomics 55:523-532 (1996); Parente (Jr), J A., et al, J. Biol. Chem. 277:20096-20101 (1996); Proux, V., et al, J. Biol Chem. 277:30790-30797 (1996)), they exhibit insufficient homology with proteins of known function as to permit their inclusion in an existing protein family. That D52 represents the first member of a novel protein family was confirmed by the identification of the hD53 gene, whose predicted product is 52% identical/66% conserved with respect to hD52 (Byrne, J.A., et al, Genomics 55:523-532 (1996)). The existence oϊhD53 was first indicated by several expressed sequence tags (ESTs) which showed significant levels of identity with regions of hD52 (Byrne, J.A., et al, Genomics 55:523-532 (1996)). The corresponding cDNA clones were obtained, and one was used to isolate full-length cDNAs from the same breast carcinoma cDNA library used for the identification of the original hD52 cDNA (Byrne, J.A., etal, Cancer Res. 55:2896-2903 (1995)). That /?Z)55 transcripts derive from a separate gene was demonstrated by the distinct chromosomal localizations for the hD52 and hD53 loci, on human chromosomes 8q21 (Byrne, J.A., et al, Cancer Res. 55:2896-2903 (1995)) and 6q22-q23 (Byrne, J.A., et al, Genomics 55:523-532 (1996)), respectively. The existence of a coiled-coil domain in D52-like molecules was predicted (Byrne, J.A., et al, Genomics 55:523-532 (1996); Chen, S-L., et al, Oncogene 72:741-751 (1996) and; Proux, V., et al, J. Biol. Chem. 277:30790-30797 (1996)), which in turn suggests that their functions involve protein-protein interactions. The coiled-coil domains of D52-like proteins are highly conserved both with respect to their sequences, lengths, and locations within D52-like proteins. That a functional relationship may exist between hD52 and hD53 gene products was indicated by examples of similar regulation of hD52 and hD53 transcript levels in both breast carcinoma and leukemic cell lines, despite the fact that hD52 and hD53 transcripts derive from separate genes located on independent chromosomes (Byrne, J.A., et al, Genomics 55:523-532 (1996)). This suggestion of a functional relationship between hD52 and hD53, combined with the degree of conservation between their coiled-coil domains, and the fact that hD52 and hD53 could be either co- or independently expressed, led to the hypothesis that hD52 and hD53 proteins may be capable of both homo- and heteromer formation (Byrne, J.A., et al, Genomics 55:523-532 (1996)). Breast cancer Despite earlier detection and a lower size of the primary tumors at the time of diagnosis (Nystrόm, L. etal, Lancet 341: 973 -978 (1993); Fletcher, S.W. etα/., J. Natl Cancer Inst. 55: 1644-1656 (1993)), associated metastases remain the major cause of breast cancer mortality (Frost, P. & Levin, R., Lancet 339: 1458- 1461 (1992)). The initial steps of transformation characterized by the malignant cell escape from normal cell cycle controls are driven by the expression of dominant oncogenes and/or the loss of tumor suppressor genes (Hunter, T & Pines, J , Cell 79 573-582 (1994)) Tumor progression can be considered as the ability of the malignant cells to leave the primary tumoral site and, after migration through lymphatic or blood vessels, to grow at a distance in host tissue and form a secondary tumor (Fidler, I } , Cancer Res. 50 6130-6138 (1990), Liotta, L etal, Cell 64 327-336 (1991)) Progression to metastasis is dependent not only upon transformation but also upon the outcome of a cascade of interactions between the malignant cells and the host cells/tissues These interactions may reflect molecular modification of synthesis and/or of activity of different gene products both in malignant and host cells Several genes involved in the control of tumoral progression have been identified and shown to be implicated in cell adhesion, extracellular matrix degradation, immune surveillance, growth factor synthesis and/or angiogenesis (reviewed in, Hart, I R & Saini, A , Lancet 339 1453-1461 (1992), Ponta, H et al, B.B.A. 7198 1 - 10 ( 1994), Bernstein, L R & Liotta, L A , Curr. Opin. Oncol. 6 106-113 (1994), Brattain, M G et al, Curr. Opin. Oncol. 6 77-81 (1994), and Fidler, I J & Ellis, L M , Cell 79 185-188 (1994)) However, defining the mechanisms involved in the formation and growth of metastases is still a major challenge in breast cancer research (Rusciano, D & Burger, M M , BwEssays 14 185-194 (1992), Hoskins, K & Weber, B L , Current Opinion in Oncology 6 554-559 (1994)) The processes leading to the formation of metastases are complex (Fidler, I J , Cancer Res. 50 6130-6138 (1990), Liotta, L et al, Cell 64 327-336 (1991)), and identifying the related molecular events is thus critical for the selection of optimal treatments Summary of the Invention The present inventors have identified a novel isoform of hD53, +5 hD53, the murine homolog of hD53, mD53 , and a novel member of the D52 gene family, hD54 +5hD53, mD53, and hD54 are useful as breast cancer prognosticators Accordingly, the present invention provides isolated nucleic acid molecules encoding the +5 hD53, murine (m) D53, or hD54 polypeptides whose amino acid sequences are shown in Figures 1, 3, and 16, respectively. Further embodiments of the invention include isolated nucleic acid molecules that are at least 90% and preferably at least 95%, 96%, 97%, 98% or 99% identical the above- described isolated nucleic acid molecules of the present invention. The present invention also relates to vectors which contain the above- described isolated nucleic acid molecules, host cells transformed with the vectors and the production of +5 hD53, mD53, orhD54 polypeptides or fragments thereof by recombinant techniques. The present invention further provides an isolated +5 hD53, mD53 or HD54 polypeptide having the amino acid sequence as shown in Figure 1 , 3 , or 16, respectively. Brief Description of the Figures Figure 1. Figure 1 shows the cDNA (SEQ ID NO: 1) and deduced amino acid sequence (SEQ ID NO:2) of +5 hD53. Figure 2. Figure 2 shows a comparison of the amino acid sequences of +5 hD53 (SEQ ID NO:2) and hD53 (SEQ ID NO:9). Figure 3. Figure 3 shows the cDNA (SEQ ID NO: 3) and deduced amino acids sequence (SEQ ID NO:4) of mD53. Figure 4. Figure 4 shows a comparison of the amino acid sequences of mD53 (SEQ ID NO:4) and hD53 (SEQ ID NO:9). Figure 5. Figure 5 shows the global alignment of D52-like sequences tested in the yeast two-hybrid system, as produced by the program CLUSTAL (Thompson, J.D., et al, Nucleic Acids Res. 22:4673-4680 (1994)): mD52 (SEQ ID NO: 1 1), hD52 (SEQ ID NO: 13), hD53 (SEQ ID NO:9), hD54+ins2 (SEQ ID NO:6), hD54-ins2 (SEQ ID NO: 15) and hD54T (SEQ ID NO: 17). The coiled- coil domain predicted in each D52-like protein is shown in bold. Two alternatively-spliced regions, ins2 and ins3, are indicated, and the hD54T amino acid sequence which shows no similarity to other D52-like sequences (due to a frame-shift in the corresponding cDNA sequence) is underlined. Numbers refer to sequence positions of the first and last amino acids shown in each line. Figures 6A-6E. Figures 6A-6E show the interactions between GST- mD52 and in v/ ' tro-translated D52-like proteins in GST pull-down assays, as demonstrated by Coomassie Brilliant Blue staining (B, D) and autoradiographic exposure (C, E) of proteins eluted from glutathione-agarose. In vitro translation reactions included pTLl constructs bearing no insert (lane 1), or mD52 (lane 2), hD52 (lane 3) or hD54-ins2 (lane 4) coding sequences. (A) 35 S-labelled protein resulting from in vitro translation of pTLl constructs. In vitro translation of mD52 and hD52 coding sequences gave single 28 kDa 35 S-labelled proteins (lanes 2 and 3), whereas in vitro translation of the hD54-ins2 coding sequence gave a single 31 kDa 35 S-labelled protein (lane 4). (B) Coomassie blue-stained GST protein (26 kDa) eluted from glutathione agarose. (C) Autoradiographic exposure (10 days) of the same gel indicate that in-vitro translated D52-like proteins were not retained on glutathione-agarose to which GST had been bound. (D) Coomassie blue-stained GST-mD52 protein (47 kDa) eluted from glutathione agarose. (E) Autoradiographic exposure (10 days) of the same gel indicated that in-vitro translated D52-like proteins were retained on glutathione-agarose to which GST-mD52 had been bound. Figure 7. Figure 7 shows an idiogram of the WMP mouse Rb (Taylor, B.A., et al, Ma m. Genome <5:S190-S200 (1996)) chromosome indicating the distribution of labeled sites on chromosome 10 using the mD53 cDNA probe. In the 100 metaphase cells examined, there were 204 silver grains associated with chromosomes and 47 of these (23%) were located on chromosome 10. The distribution of grains on chromosome 10 was not random, 37/47 (78.7%) of them mapping to the A4-B2 region. Figure 8. Global alignment of hD52 (SEQ ID NO: 13), RIO (SEQ ID NO: 19) (Proux, V., etal., J. Biol Chem. 277:30790-30797 (1996)), hD53 (SEQ ID NO:9), 192334 (SEQ ID NO:8), hD54+ins2/Hl l/L12 (SEQ ID NO:6), hD54-ins2/Gl 1 (SEQ ID NO: 15), hD54T/D12/Dl A(SEQ ID NO: 17) amino acid sequences. Four insertions of 4 or more residues are shown in bold and labeled insl, ins2, ins3 and ins4. The coiled-coil domain of hD54 is boxed. The C- terminal 42 amino acids of the hD54T/D12/DlA sequence which shows no homology with the other D52-like sequences aligned is shown in italics. Figure 9. Variation within hD54+ins2, hD54-ins2, hD54T nucleotide (SEQ ID NOs:5, 14, and 16, respectively) and deduced amino acid sequences (SEQ ID NO:6, 15, and 17, respectively). Arrows border nucleotide sequences that are present in hD54+ins2 but not in hD54-ins2 or hD54T. The 3 nucleotides before and after alternative coding sequences are shown in bold with a line above or below the sequence. Figure 10. Alignment of the D52 motifs present in the sequences of D52- like proteins: hD52 (SEQ ID NO: 13), mD52 (SEQ ID NO: 11), CSPP28 (SEQ ID NO:20)(Parente (Jr), J A., et al, J. Biol. Chem. 277:20096-20101 (1996)), R10 (SEQ ID NO: 19) (Proux, V., et al, J. Biol Chem. 277:30790-30797 (1996)), hD53 (SEQ ID NO:9), mD53 (SEQ ID NO:4), hD54-ins2 (SEQ ID NO: 15) and hD54+ins2 (SEQ ID NO:6). The consensus sequence (SEQ ID NO:21) is shown below these sequences, and residues which are conserved in accordance with this consensus are shown in bold. hD54+ins2 (1) and hD54+ins2 (2) refer to the more N- and C-terminal D52 motifs respectively, created by the presence of ins2. Figure 11. Mapping of the hD54 locus to chromosome 20ql3 2-ql3 3 Idiogram of human chromosome 20 illustrating the distribution of labeled sites obtained with the 192334 cDNA Figure 12. RT-PCR analysis of D54 coding sequence heterogeneity PCR products obtained by amplification of rat D54 regions flanking sequences encoding (A) ins 1 , (B) ins2 and (C) ins3 &4 Letters above each lane in panel A refer to the tissue used in reverse transcriptase cDNA synthesis reactions (b, brain and 1, liver) Results obtained in brain or liver were representative of those obtained in skeletal muscle, cardiac atrium, stomach, testis and kidney samples, at the respective developmental time-points examined Plus symbols appear above lanes where the template for PCR reactions was hD54 cDNA (hD54+ιns2/Hll, panels A, B and C, and additional lane, hD54-ιns2/Gll, panel B) PCR control reactions where cDNA template was emitted are indicated by a minus symbol Size markers and PCR product sizes are indicated in bp to the left and right of each panel, respectively Alignments of PCR product sequences with hD54 (SEQ ID NO.5) or 192334 (SEQ ID NO 7) sequence regions are shown below each panel Insl, ins2 and ins3 sequences, and the nucleotide sequences encoding these, are shown in bold Nucleotide sequences of PCR products are translated below each sequence, with residues underlined being predicted by all nucleotide sequences in each alignment Figure 13. RT-PCR analysis ofD52 coding sequence heterogeneity PCR products obtained by amplification of rat D52 regions flanking sequences encoding (A) ins 1 , (B) ins2 and (C) ins3&4 Letters above each lane in panel A refer to the tissue used in reverse transcriptase cDNA synthesis reactions (b, brain and 1, liver) Results obtained in liver represent those obtained in skeletal muscle, cardiac atrium, stomach, testis and kidney samples, at the respective developmental time- points examined A plus symbol appears above lanes where the template for PCR reactions was mD52 cDNA PCR control reactions where cDNA template was omitted are indicated by a minus symbol Size markers and PCR product sizes are indicated in bp to the left and right of each panel, respectively Alignment of PCR product sequences with mD52 sequence (SEQ ID NO 10) and RIO (SEQ ID NO 18) regions are shown below each panel Ins3 sequences, and the nucleotide sequences encoding these, are shown in bold Nucleotide sequences of PCR products are translated below each sequence, with residues underlined being predicted by all nucleotide sequences in each alignment Figure 14. RT-PCR analysis of D53 coding sequence heterogeneity (A) PCR products obtained by amplification of rat 7355 regions flanking sequences encoding insl, ins2 and ins3&4 Letters above each lane refer to the adult rat tissue used in reverse transcriptase cDNA synthesis reactions (a, cardiac atrium, s, stomach, 1, liver and k, kidney) A plus symbol appears above lanes where the template for PCR reactions was mD53 cDNA PCR control reactions where cDNA template was omitted are indicated by a minus symbol Size markers and PCR product sizes are indicated in bp to the left and right of each panel, respectively (B) Alignments of PCR product sequences with mD53 (SEQ ED NO 3) sequence regions Ins3 and ins4 sequences, and the nucleotide sequences encoding these, are shown in bold Translated amino acid sequences appear above or below their corresponding nucleotide sequences, with residues underlined being predicted by all nucleotide sequences in each alignment Figure 15. The hD52 EST W25876 Alignment of hD52 (SEQ ID NO.12) (Byrne, J A., etal, Cancer Res. 55.2896-2903 (1995)), W25876 (SEQ ID NO 38) and RIO (SEQ ID NO 18) (Proux, V , et al, J. Biol. Chem. 271 30790-30797 (1996)) nucleotide sequences The translated R10 amino acid sequence (SEQ ID NO 19) appears below the alignment, with residues underlined being also predicted by hD52 and W25876 sequences Sequence insertions present in W25876 with respect to the hD52 sequence (nucleotides 82-151 and 254-419) are labeled above the alignment Ins3 sequences and the nucleotide sequences encoding these, are shown in bold Figure 16. The nucleotide (SEQ ID NO 5) and deduced amino acid (SEQ ID NO 6) sequence of hD54 Figure 17A-B. ESTs with homology to D53 AA182908 (SEQ ID NO 63), W93489 (SEQ ID NO 64), AA240722 (SEQ ID NO 65), AA278103 (SEQ ID NO 66), AA066421(SEQ ID NO 67), T89899 (SEQ ID NO 68), T93647 (SEQ ID NO 69), W69680 (SEQ ID NO 70), AA055718 (SEQ ID NO 71), T68402 (SEQIDNO 72), Wl 1611 (SEQ ID NO 73), W14257 (SEQ ID NO 74), and N99206 (SEQ ID NO 75) Figure 18A-D. ESTs with homology to D54 AA004043 (SEQ ID NO 76), AA008731 (SEQ ID NO 77), AA031903 (SEQ ID NO 78), AA103819 (SEQ ID NO 79), AA124904 (SEQ ID NO 80), W10501 (SEQ ID NO 81), W20813 (SEQ ID NO 82), W54810 (SEQ ID NO 83), W66669 (SEQ ID NO 84), W82290 (SEQ ID NO 85), W91446 (SEQ ID NO 86), W97219 (SEQ ID NO 87), AA218395 (SEQ ID NO 88), AA268015 (SEQ ID NO 89), AA266320 (SEQ ID NO 90), AA255184 (SEQ ID NO 91), W75292 (SEQ ID NO 92), AA048792 (SEQ ID NO 93), H31879 (SEQ ID NO 94), AA277778 (SEQ ID NO 95), W13944 (SEQ ID NO 96), H39077 (SEQ ID NO 97), AA411964 (SEQ ID NO 98), AA124922 (SEQ ID NO 99), AA116313 (SEQ ID NO 100), W75408 (SEQ ID NO 101), and AA436748 (SEQ ID NO 102) Detailed Description of the Invention +5hD53, mD53, and hD54 Nucleic Acid Molecules, Polypeptides and Fragments Thereof The present inventors have identified an isoform of hD53, termed +5 hD53, from a human breast carcinoma cDNA library D53 was described in WO97/06256, which is herein incorporated by reference The present inventors have also identified a mouse cDNA exhibiting a high level of homology to the hD53 cDNA The mouse D53 (mD53) cDNA was isolated from an embryonic stem cell cDNA library using an 842 bp hD53 cDNA as a probe (Byrne, J.A., et al, Genomics 55:523-532 (1996)) The 1307 bp mD53 cDNA (SEQ ID NO 3) includes a 615 bp coding region which predicts a 204 amino acid protein (SEQ ID NO 4) The hD53 and mD53 proteins are predicted to be 91% identical/93%) conserved, and as such are more highly conserved than the majority of orthologous mouse and human proteins (Makalowski, W., et al, Genome Res. 5:846-857 (1996)) The present inventors have also identified a novel member of the D52 family, D54 The 2302 bp hD54 cDNA (SEQ ID NO 4) includes a 621 bp coding region which predicts a 206 amino acid protein (SEQ ID NO 5). The polypeptide sequence of hD54 is 56% and 51% identical/67%) and 60% similar to those of hD52 and hD53, respectively +5hD53, mD53 and hD54 are useful as breast cancer prognosticators, as described for D52 family members in WO97/06256, which is herein incorporated by reference Using the information provided herein, such as the nucleotide sequences of +5 hD53, mD53 or hD54 as set out in Figures 1, 3, and 16, respectively (SEQ ID NOS 1, 3, and 5), an isolated nucleic acid molecule of the present invention may be obtained using standard cloning and screening procedures, such as those for cloning cDNAs using mRNA as starting material By "isolated" nucleic acid molecules(s) is intended a nucleic acid molecule, DNA or RNA, which has been removed from its native environment For example, recombinant DNA molecules contained in a vector are considered isolated for purposes of the invention as are recombinant DNA molecules maintained in heterologous host cells or purified (partially or substantially) DNA molecules in solution Isolated RNA molecules include in vitro RNA transcripts of the DNA molecules of the present invention By "isolated" polypeptide or protein is intended a polypeptide or protein removed from its native environment For example, recombinantly produced polypeptides and proteins expressed in host cells are considered isolated for purposes of the invention, as are native or recombinant polypeptides which have been partially or substantially purified by any suitable technique such as, for example, the single-step purification method disclosed in Smith and Johnson, Gene (57:31-40 (1988) Isolated nucleic acid molecules and polypeptides also include such compounds produced synthetically As indicated, nucleic acid molecules of the present invention may be in the form of RNA, such as mRNA, or in the form of DNA, including, for instance, cDNA and genomic DNA obtained by cloning or produced synthetically The DNA may be double- or single-stranded Single-stranded DNA may be the coding strand, also known as the sense strand, or it may be the noncoding strand, also referred to as the antisense strand +5 hD53 The present invention provides isolated nucleic acid molecules comprising a polynucleotide encoding the +5 hD53 polypeptide whose amino acid sequence is shown Figure 1 (SEQ ID NO 2) or a fragment thereof Such isolated nucleic acid molecules include DNA molecules comprising an open reading frame (ORF) starting at position 1 of the nucleotide sequence of Figure 1 (SEQ ID NO 1) and further include DNA molecules which comprise a sequence substantially different than all or part of the ORF starting at position 1 of the nucleotide sequence of Figure 1 (SEQ ID NO: 1) but which, due to the degeneracy of the genetic code, still encode the +5 hD53 polypeptide or a fragment thereof. Of course, the genetic code is well known in the art. Thus, it would be routine for one skilled in the art to generate the degenerate DNA molecules above. The invention further provides an isolated nucleic acid molecule having the nucleotide sequence shown in Figure 1 (SEQ ID NO:l) or a fragment thereof. Such isolated DNA molecules and fragments thereof are useful as DNA probes for gene mapping by in situ hybridization with chromosomes and for detecting expression of the D53 gene in human tissue (including breast and lymph node tissues) by Northern blot analysis. mD53 The present invention also provides isolated nucleic acid molecules comprising a polynucleotide encoding the mD53 polypeptide whose amino acid sequence is shown Figure 3 (SEQ ID NO:4) or a fragment thereof. Such isolated nucleic acid molecules include DNA molecules comprising an open reading frame (ORF) whose initiation codon is at position 192-194 of the nucleotide sequence of Figure 3 (SEQ ID NO:3) and further include DNA molecules which comprise a sequence substantially different than all or part of the ORF whose initiation codon is at position 192-194 of the nucleotide sequence of Figure 3 (SEQ ID NO: 3) but which, due to the degeneracy of the genetic code, still encode the mD53 polypeptide or a fragment thereof. Of course, the genetic code is well known in the art. Thus, it would be routine for one skilled in the art to generate the degenerate DNA molecules above. The invention also provides an isolated nucleic acid molecule encoding the mD53 polypeptide as shown in SEQ ID NO:4, but lacking the N-terminal methionine. The invention further provides an isolated DNA molecule having the nucleotide sequence shown in Figure 3 (SEQ ID NO:3) or a fragment thereof. Such isolated DNA molecules and fragments thereof are useful as DNA probes for gene mapping by in situ hybridization with chromosomes and for detecting expression of the murine or human D53 gene in mouse or human tissue (including breast and lymph node tissues) by Northern blot analysis Of course, as discussed above, if a DNA molecule includes the ORF whose initiation codon is at position 192-194 of Figure 3 (SEQ ID NO 3), then it is also useful for expressing the murine D53 polypeptide or a fragment thereof hD54 The present invention also provides isolated nucleic acid molecules compπsing a polynucleotide encoding the hD54 polypeptide whose amino acid sequence is shown Figure 16(SEQ ID NO 6) or a fragment thereof Such isolated nucleic acid molecules include DNA molecules comprising an open reading frame (ORF) whose initiation codon is at position 77-79 of the nucleotide sequence of Figure 16 (SEQ ID NO 5) and further include DNA molecules which comprise a sequence substantially different than all or part of the ORF whose initiation codon is at position 77-79 of the nucleotide sequence of Figure 16 (SEQ ID NO 5) but which, due to the degeneracy of the genetic code, still encode the hD54 polypeptide or a fragment thereof Of course, the genetic code is well known m the art Thus, it would be routine for one skilled in the art to generate the degenerate DNA molecules above The invention also provides an isolated nucleic acid molecule encoding the hD54 polypeptide as shown in SEQ ID NO 6, but lacking the N-terminal methionine The invention further provides an isolated DNA molecule having the nucleotide sequence shown in Figure 16 (SEQ ID NO 5) or a fragment thereof Such isolated DNA molecules and fragments thereof are useful as DNA probes for gene mapping by in situ hybridization with chromosomes and for detecting expression of the murine or human D54 gene in mouse or human tissue (including breast and lymph node tissues) by Northern blot analysis. Of course, as discussed above, if a DNA molecule includes the ORF whose initiation codon is at position 77-79 of Figure 16 (SEQ ID NO: 5), then it is also useful for expressing the hD54 polypeptide or a fragment thereof. Fragments, Derivatives and Variants of the Isolated Nucleic Acid Molecules of the Invention By "fragments" of an isolated DNA molecule having the nucleotide sequence shown in Figure 1, 3, or 16 (SEQ ID NO: l, 3, or 5 respectively) are intended DNA fragments at least 15 bp, preferably at least 20 bp, and more preferably at least 30 bp in length which are useful as DNA probes as discussed above. Of course, larger DNA fragments of about 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, or 1050-2000 bp in length are also useful as DNA probes according to the present invention as are DNA fragments corresponding to most, if not all, of the nucleotide sequence shown in Figure 1, 3, or 16 (SEQ ID NO: l, 3, or 5 respectively). By a fragment at least 20 bp in length, for example, is intended fragments which include 20 or more contiguous bases from the nucleotide sequence shown in Figure 1, 3, or 16 (SEQ ID NO: l, 3, or 5 respectively). As indicated, such fragments are useful diagnostically either as a probe according to conventional DNA hybridization techniques or as primers for amplification of a target sequence by the polymerase chain reaction (PCR). Since the +5 hD53, mD53, and hD54 genes are shown in Figures 1, 3, and 16 respectively (SEQ ID NO: l , 3, and 5 respectively) are provided, generating such DNA fragments of the present invention would be routine to the skilled artisan. For example, restriction endonuclease cleavage or shearing by sonication could easily be used to generate fragments of various sizes. Alternatively, the DNA fragments of the present invention could be generated synthetically according to known techniques. Preferred nucleic acid molecules of the present invention will encode the mature form of the +5 hD53, mD53, or hD54 protein and/or additional sequences, such as those encoding a leader sequence, or the coding sequence of the mature polypeptide, with or without the aforementioned additional coding sequences, together with additional, noncoding sequences, including for example, but not limited to introns and noncoding 5' and 3' sequences such as the transcribed, nontranslated sequences that play a role in transcription, mRNA processing (including splicing and polyadenylation signals), ribosome binding, and mRNA stability; and additional coding sequence which codes for additional amino acids, such as those which provide additional functionalities. Thus, for instance, the polypeptide may be fused to a marker sequence, such as a peptide, which facilitates purification of the fused polypeptide. In certain preferred embodiments of this aspect of the invention, the marker sequence is a hexa-histidine peptide, such as the tag provided in a pQE vector (Qiagen, Inc.), among others, many of which are commercially available. As described in Gentz et al, Proc. Natl. Acad. Sci. USA 86: 821-824 (1989), for example, hexa-histidine provides for convenient purification of the fusion protein. The HA tag corresponds to an epitope derived of influenza hemagglutinin protein, which has been described by Wilson et al. , Cell 57:767 (1984). The present invention further relates to variants of the isolated nucleic acid molecules of the present invention, which encode fragments, analogs or derivatives of the +5 hD53, mD53, or hD54 protein. Variants may occur naturally, such as an allelic variant. Non-naturally occurring variants may be produced using art-known mutagenesis techniques, which include those produced by nucleotide substitutions, deletions or additions. Especially preferred among these are silent or conservative substitutions, additions and deletions, which do not alter the properties and activities of the +5 hD53, mD53, or hD54 protein or fragment thereof. Further embodiments of the invention include isolated nucleic acid molecules that are at least 90% identical, and more preferably at least 95%, 96%, 97%), 98% or 99% identical to the above-described isolated nucleic acid molecules of the present invention. In particular, the invention is directed to isolated nucleic acid molecules at least 90%, 95%, 96%, 97%, 98%, or 99% identical to the nucleotide sequences contained in Figures 1, 3 or 16 (SEQ ID NO: l, 3, or 5, respectively). By the invention, "% identity" between two nucleic acid sequences can be determined using the "fastA" computer algorithm (Pearson, W.R. & Lipman, D. J., Proc. Nail Acad. Sci. USA 55:2444 (1988)) with the default parameters. Uses of such 95%, 97%o, 98%, or 99% identical nucleic acid molecules of the present invention include, inter alia, (1) isolating the hD53, +5 hD53, mD53, or hD54 gene or allelic variants thereof in a cDNA library; (2) in situ hybridization (FISH) to metaphase chromosomal spreads to provide precise chromosomal location of the hD53, mD53, or hD54 gene as described in Verma et al, HUMAN CHROMOSOMES: AMANUAL OF BASIC TECHNIQUES (Pergamon Press, NY, 1988); and (3) Northern Blot analysis for detecting hD53, +5 hD53, mD53, or hD54 mRNA expression in specific tissues. Guidance concerning how to make phenotypically silent amino acid substitutions is provided in Bowie, J.U. et al, Science 247: 1306-1310 (1990), wherein the authors indicate that there are two main approaches for studying the tolerance of an amino acid sequence to change. The first method relies on the process of evolution, in which mutations are either accepted or rejected by natural selection. The second approach uses genetic engineering to introduce amino acid changes at specific positions of a cloned gene and selections or screens to identify sequences that maintain functionality. As the authors state, these studies have revealed that proteins are surprisingly tolerant of amino acid substitutions. The authors further indicate which amino acid changes are likely to be permissive at a certain position of the protein. For example, most buried amino acid residues require nonpolar side chains, whereas few features of surface side chains are generally conserved. Other such phenotypically silent substitutions are described in Bowie, J.U., et al, Science 2-77: 1306-1310 (1990), and the references cited therein. The invention is further related to nucleic acid molecules capable of hybridizing to a nucleic acid molecule having a sequence complementary to or hybridizing directly to the nucleic acid sequence shown in Figure 1 , 3 , or 16 (SEQ ID NO: l, 3, or 5 respectively) under stringent conditions. By "stringent conditions" is intended overnight incubation at 42° C in a solution comprising: 50% formamide, 5x SSC (150 mM NaCI, 15 mM trisodium citrate), 50 mM sodium phosphate (pH 7.6), 5x Denhardt's solution, 10% dextran sulfate, and 20 μg ml denatured, sheared salmon sperm DNA (ssDNA), followed by washing the filters in 0. lx SSC at about 65 °C. In a further aspect, the present invention is directed to polynucleotides having a nucleotide sequence complementary to the nucleotide sequence of any of the polynucleotides discussed above. Expressed Sequence Tags An expressed sequence tag (EST) is a segment of a sequence from a randomly selected cDNA clone that corresponds to a mRNA (Adams, M.D. et al. , Science 252: 1651-1656 (1991); Adams, M.D. etal., Nature 555:632-634 (1992); Adams, M.D. et al, Nat. Genet. 4:373-380 (1993)). The present inventors have identified the following ESTs with homology to portions of AA182908 (SEQ ID NO:63), W93489 (SEQ ID NO:64), AA240722 (SEQ ID NO:65), AA278103 (SEQ ID NO: 66), AA066421(SEQ ID NO:67), T89899 (SEQ ID NO:68), T93647 (SEQ ID NO:69), W69680 (SEQ ID NO:70), AA055718 (SEQ ID NO:71), T68402 (SEQ IDNO:72), Wl 1611 (SEQ ID NO:73), W14257 (SEQ ID NO:74), and N99206 (SEQ ID NO:75). The present inventors have also identified the following ESTs with homology to portions of hD54: AA004043 (SEQ ID NO:76), AA008731 (SEQ ID NO:77), AA031903 (SEQ ID NO:78), AA103819 (SEQ ID NO:79), AA124904 (SEQ ID NO:80), W10501 (SEQ ID NO:81), W20813 (SEQ ID NO:82), W54810 (SEQ ID NO:83), W66669 (SEQ ID NO:84), W82290 (SEQ ID NO:85), W91446 (SEQ ID NO:86), W97219 (SEQ ID NO:87), AA218395 (SEQ ID NO:88), AA268015 (SEQ ID NO:89), AA266320 (SEQ ID NO:90), AA255184 (SEQ ID NO:91), W75292 (SEQ ID NO:92), AA048792 (SEQ ID NO:93), H31879 (SEQ ID NO:94), AA277778 (SEQ IDNO:95), W13944 (SEQ ID NO: 96), H39077 (SEQ ID NO: 97), AA411964 (SEQ ID NO: 98), AA124922 (SEQ ID NO:99), AA116313 (SEQ ID NO: 100), W75408 (SEQ ID NO: 101), and AA436748 (SEQ ID NO: 102). Isolated RNA Molecules The present invention further provides isolated RNA molecules which are in vitro transcripts of a nucleic acid sequence shown in Figure 1 , 3 or 16 (SEQ ID NO:l, 3, or 5, respectively) or a fragment thereof. Such RNA molecules are useful as antisense RNA probes for detecting hD53 or mD53 gene expression by in situ hybridization. Polypeptides and Fragments Thereof +5 hD53 The invention further provides an isolated +5 hD53 polypeptide having an amino acid sequence as shown in Figure 1 (SEQ ID NO:2), or a fragment thereof. +5 hD53 is a member of the hD52 family of proteins. hD52-like proteins all contain coiled-coil domains near the N-terminus. The present inventors have shown that the hD52 family of proteins interact in homo- and heteromeric fashions both in vivo and in vitro. Indications that hD52 and hD53 coiled-coil domains were also mediating homo- and heteromeric interactions between these proteins derive from the results of yeast two-hybrid screenings, where all hD52 and hD53 interactors identified contained sequences encoding entire coiled-coil domains. The cloning of an alternatively-spliced form of hD53 during a yeast two- hybrid screening using the hD53 bait has also provided further evidence that multiple protein isoforms may be produced fromD52-like genes (Proux, V., etal, J. Biol. Chem. 277:30790-30797 (1996)). The +5 hD53 cDNA identified in the present study predicts a C-terminally truncated hD53 protein as a result of a 100 bp out-of-frame deletion. The resulting truncation occurs three residues after residue 128 (SEQ ID NO:2), which represents the first residue of an alternatively- spliced 13 amino acid region (residues 128-140 of SEQ ID NO:2) referred to as ins3. mD53 The invention further provides an isolated mD53 polypeptide having an amino acid sequence as shown in Figure 3 (SEQ ID NO:3) or a fragment thereof. The present invention also provides isolated polypeptides having an amino acid sequence of mD53 as shown in SEQ ID NO:4, but lacking the N-terminal methionine. The present inventors have discovered that the mD53 polypeptide is an about 204 amino acid residue protein having a coiled-coiled domain at the N- terminus. Interactions between mD52 and hD53 fusion proteins were found to be mediated via mD52 residues 1-95 of SEQ ID NO:4, which include the predicted coiled-coil domain at residues 29-71 of SEQ ID NO:4. hD54 The invention further provides an isolated hD54 polypeptide having an amino acid sequence as shown in Figure 16 (SEQ ID NO : 5) or a fragment thereof. The present invention also provides isolated polypeptides having an amino acid sequence of hD54 as shown in SEQ ID NO: 6, but lacking the N-terminal methionine The present inventors have discovered that the hD54 polypeptide is an about 206 amino acid residue protein having a coiled-coiled domain at the N- terminus Polypeptide Fragments and Variants Fragments of +5 hD53, mD53, or hD54 other than those described above capable of raising both monoclonal and polyclonal antibodies will be readily apparent to one of skill in the art and will generally be at least 10 ammo acids, and preferably at least 15 ammo acids, in length For example, the "good antigen" criteria set forth in Van Regenmortel et al , Immunol Letters 17 95-108 (1988), could be used for selecting fragments of the hD53, mD53, or hD54 protein capable of raising monoclonal and polyclonal antibodies It will be recognized in the art that some amino acid sequences of +5 hD53, mD53, or hD54 can be varied without significant effect on the structure or function of the protein If such differences in sequence are contemplated, it should be remembered that there will be critical areas on the protein which determine activity Such areas will usually comprise residues which make up the binding site, or which form tertiary structures which affect the binding site In general, it is possible to replace residues which form the tertiary structure, provided that residues performing a similar function are used In other instances, the type of residue may be completely unimportant if the alteration occurs at a noncπtical region of the protein Thus, the present invention further includes variations of the +5 hD53, mD53, or hD54 protein which show substantial protein activity or which include regions of the +5 hD53, mD53, or hD54 protein such as the protein fragments discussed above capable of raising antibodies useful in immunohistochemical or RIA assays Such mutants include deletions, insertions, inversions, repeats and type-substitutions (e g , substituting one hydrophilic residue for another, but not strongly hydrophilic for strongly hydrophobic as a rule). Small changes or such "neutral" amino acid substitutions will generally have little effect on activity. Typically seen as conservative substitutions are as follows: the replacements, one for another, among the aliphatic amino acids, Ala, Val, Leu and He; interchange of the hydroxyl residues, Ser and Thr; exchange of the acidic residues, Asp and Glu; substitution between the amide residues, Asn and Gin; exchange of the basic residues, Lys and Arg; and replacements among the aromatic residues, Phe, Tyr. As indicated in detail above, further guidance concerning which amino acid changes are likely to be phenotypically silent (i.e., are not likely to have a significant deleterious effect on a function) can be found in Bowie, J.U. et al, Science 247: 1306-1310 (1990). Preferably, such variants will be at least 90%, 95%, 96%, 97%, 98% or 99%o identical to the +5 hD53, mD53, or hD54 polypeptides described above and also include portions of such polypeptides with at least 30 amino acids and more preferably at least 50 amino acids. By the invention, "% identity" between two polypeptides can be determined using the "fastA" computer algorithm with the default parameters (Pearson, W.R. & Lipman, D.J., Proc. Natl. Acad. Sci. USA 55:2444 (1988)). The isolated hD53, mD53, or hD54 polypeptide, or a fragment thereof, are preferably provided in an isolated form, and preferably are substantially purified. Of course, purification methods are known in the art. In preferred embodiment, a recombinantly produced version of the hD53, mD53, or hD54 polypeptide is substantially purified by the one-step method described in Smith and Johnson, Gene 67: 1-40 (1988). The hD53, mD53, or hD54 protein can be recovered and purified from recombinant cell cultures by well-known methods including ammonium sulfate or ethanol precipitation, acid extraction, anion or cation exchange chromatography, phosphocellulose chromatography, hydrophobic interaction chromatography, affinity chromatography, hydroxylapatite chromatography and lectin chromatography. Most preferably, high performance liquid chromatography ("HPLC") is employed for purification. Polypeptides of the present invention include naturally purified products, products of chemical synthetic procedures, and products produced by recombinant techniques from a prokaryotic or eukaryotic host, including, for example, bacterial, yeast, higher plant, insect and mammalian cells Depending upon the host employed in a recombinant production procedure, the polypeptides of the present invention may be glycosylated or may be nonglycosylated In addition, polypeptides of the invention may also include an initial modified methionine residue, and in some cases as a result of host-mediated processes Vectors and Hosts The present invention also relates to vectors which include an isolated DNA molecule(s) of the present invention, host cells which are genetically engineered with the vectors, and the production of +5 hD53, mD53, or hD54 polypeptιde(s), or fragments thereof, by recombinant techniques A DNA molecule, preferably a cDNA, encoding the +5 hD53, mD53, or hD54 polypeptide or a fragment thereof, may easily be inserted into a suitable vector Ideally, the vector has suitable restriction sites for ease of insertion, but blunt-end ligation, for example, may also be used, although this may lead to uncertainty over reading frame and direction of insertion The +5 hD53, mD53, or hD54 polypeptιde(s), or fragments thereof, can be expressed in any suitable host cell The extent of expression may be analyzed by SDS polyacrylamide gel electrophoresis (Laemmelh, et al , Nature 227 680- 685 (1970)) Cultures useful for production of such polypeptides include prokaryotic, eukaryotic and yeast expression systems Preferred systems include E coli, Streptomyces and Salmonella typhimurium and yeast, mammalian or plant cells Mammalian hosts include HeLa, COS, and Chinese Hamster Ovary (CHO) cells Yeast hosts include S cerevisiae Insect cells include Drosophila S2 and Spodoptera Sf9 cells Appropriate culture mediums and conditions for the above- described host cells are known in the art. Vectors capable of directing expression in the above-mentioned host cells are also known in the art. hD54 as a Breast Cancer Prognosticator The hD54 gene of the present invention encodes a polypeptide which is useful as a prognostic marker for breast cancer. It is known in the art that prognostic markers provide important information in the management of breast cancer patients (Elias etal, J. Histotechnol. 15(4):315-320 (1992)). For example, for application of systemic adjuvant therapy in primary breast cancer, identification of high- and low-risk patients is a major issue (McGuire, W.L., N. Engl J. Med. 320:525-527 (1989)). Several classical (tumor size, lymph node status, histopathology, steroid receptor status) and second-generation prognostic factors (proliferation rate, DΝA ploidy, oncogenes, growth factor receptors and some glycoproteins) are currently available for making therapeutic decisions (McGuire, W.L., Prognostic Factors for Recurrence and Survival, in EDUCATIONAL BOOKLET AMERICAN SOCIETY OF CLINICAL ONCOLOGY, 25th Annual Meeting, 89- 92 (1989); Contesso et al, Eur. J. Clin. Oncol 25:403-409 (1989)). Although no group of the art-known prognosticators completely fulfills the objective to fully distinguish high- and low-risk patients, combinations of the prognostic factors can improve the prediction of a patient's prognosis (McGuire, W.L., N. Engl. J. Med. 520:525-527 (1989)). Thus, by the invention, a further prognostic marker is provided which can be added to the population of art-known prognosticators to more particularly distinguish between high- and low-risk breast cancer patients. The present inventors have discovered that, in many instances, cells obtained from breast tumors contain significantly greater copy number of hD54 and express significantly enhanced levels of hD54 mRΝA and/or protein when compared to cells obtained from "normal" breast tissue, i.e., non-tumorigenic breast tissue. Thus, the invention provides a method useful during breast cancer prognosis, which involves assaying a first hD54 gene expression level or gene copy number in breast tissue and comparing the gene expression level or gene copy number with a second hD54 gene expression level or gene copy number, whereby the relative levels of said first gene expression level or gene copy number over said second is a prognostic marker for breast cancer By the invention, gene amplification and enhanced gene expression over the standard is clinically relevant for breast cancer prognosis as independent studies have shown an association between the presence of amplification and an increased risk of relapse (Slamon et al, Science 255: 177 (1987), Ravdin & Chamness, Gene 759:19 (1995)) The methods of the invention can be used alone or together with other markers known in the art for breast cancer prognosis, including those discussed above By "assaying hD54 gene expression level" is intended qualitatively or quantitatively measuring or estimating the hD54 protein level or hD54 mRNA level in a first biological sample either directly or relatively by comparing to the hD54 protein level or mRNA level in a second biological sample By "assaying hD54 gene copy number" is intended qualitatively or quantitatively measuring or estimating hD54 gene copy number in a first biological sample either directly or relatively by comparing to the hD54 gene copy number in a second biological sample Preferably, the hD54 protein level, mRNA level, or gene copy number in the first biological sample is measured or estimated and compared to a second standard hD54 protein level, mRNA level, or gene copy number, the standard being taken from a second biological sample obtained from an individual not having breast cancer As will be appreciated in the art, once a standard hD54 protein level, mRNA level, or gene copy number is known, it can be used repeatedly as a standard for comparison It will also be appreciated in the art, however, that the first and second biological samples can both be obtained from individuals having breast cancer In such a scenario, the relative hD54 protein levels, mRNA levels or gene copy numbers will provide a relative prognosis between the individuals By "biological sample" is intended any biological sample obtained from an individual, cell line, tissue culture, or other source which contains hD54 protein, mRNA, or gene Preferably, the biological sample includes tumoπgenic or non-tumoπgenic breast tissue Methods for obtaining tissue biopsies are well known in the art The present invention is useful as a prognostic indicator for breast cancer in mammals Preferred mammals include monkeys, apes, cats, dogs, cows, pigs, horses, rabbits and humans Particularly preferred are humans Assaying hD54 gene copy number can occur according to any known technique such as, for example, by visualizing extrachromosomal double minutes (dmin) or integrated homogeneously staining regions (hsrs) (Gebhart etal , Breast Cancer Res Treat 5 125 (1986), Dutπllaux et al , Cancer Genet Cytogenet 49 203 (1990)) Other techniques such as comparative genomic hybridization (CGH) and a strategy based on chromosome microdissection and fluorescence in situ hybridization can also be used to search for regions of increased DNA copy number in tumor cells (Guan et al , Nature Genet 5 155 (1994), Muleπs et al , Genes Chrom Cancer 10 160 (1994)) DNA probes that hybridize to the hD54 can be prepared as described below Total cellular RNA can be isolated from normal and tumoπgenic breast tissue using any suitable technique such as the single-step guanidinium- thiocyanate-phenol-chloroform method described in Chomczynski and Sacchi, Anal Biochem 162 156-159 (1987) The LiCL/urea method described in Auffray and Rougeon, Eur J Biochem 107 303 (1980) can also be used hD54 mRNA levels are then assayed using any appropriate method These include Northern blot analysis, S 1 nuclease mapping, the polymerase chain reaction (PCR), reverse transcription in combination with the polymerase chain reaction (RT-PCR), and reverse transcription in combination with the ligase chain reaction (RT-LCR) Northern blot analysis can be performed as described in Harada et al , Cell 63 303-312 (1990) Briefly, total RNA is prepared from a biological sample as described above For the Northern blot, the RNA is denatured in an appropriate buffer (such as glyoxal/dimethyl, sulfoxide/sodium phosphate buffer), subjected to agarose gel electrophoresis, and transferred onto a nitrocellulose or nylon filter hD54 DNA labeled according to any appropriate method (such as the 32 P- multiprimed DNA labeling system (Amersham)) is used as probe After hybridization, the filter is washed and exposed to x-ray film hD54 DNA for use as probes according to the present invention are described below Where a fragment is used, the DNA probe will be at least about 15-30 nucleotides in length, and preferably, at least about 50 nucleotides in length SI mapping can be performed as described in Fujita et al, Cell 49:357- 367 (1987) To prepare probe DNA for use in SI mapping, the sense strand of hD54 cDNA is used as a template to synthesize labeled antisense DNA The antisense DNA can then be digested using an appropriate restriction endonuclease to generate further DNA probes of a desired length Such antisense probes are useful for visualizing protected bands corresponding to hD54 mRNA Northern blot analysis can be performed as described above Alternatively, hD54 mRNA levels are assayed using the RT-PCR method described in Makino et al., Technique 2:295-301 (1990) By this method, the radioactivities of the amplification products in the polyacrylamide gel bands are linearly related to the initial concentration of the target mRNA Briefly, this method involves adding total RNA isolated from a biological sample in a reaction mixture containing a RT primer and appropriate buffer After incubating for primer annealing, the mixture can be supplemented with a RT buffer, dNTPs, DTT, RNase inhibitor and reverse transcriptase After incubation to achieve reverse transcription of the RNA, the RT products are then subject to PCR using labeled primers Alternatively, rather than labeling the primers, a labeled dNTP can be included in the PCR reaction mixture PCR amplification can be performed in a DNA thermal cycler according to conventional techniques After a suitable number of rounds to achieve amplification, the PCR reaction mixture is electrophoresed on a polyacrylamide gel After drying the gel, the radioactivity of the appropriate bands (corresponding to the hD54 mRNA) is quantified using an imaging analyzer. RT and PCR reaction ingredients and conditions, reagent and gel concentrations, and labeling methods are well known in the art. Variations on the RT-PCR method will be apparent to the skilled artisan. Any set of oligonucleotide primers which will amplify reverse transcribed hD54 mRNA can be used and can be designed by reference to the hD54 DNA sequence provided below. Assaying hD54 protein levels in a biological sample can occur using any art-known method. Preferred are antibody-based techniques. For example, hD54 protein expression in tissues can be studied with classical immunohistological methods. In these, the specific recognition is provided by the primary antibody (polyclonal or monoclonal) but the secondary detection system can utilize fluorescent, enzyme, or other conjugated secondary antibodies. As a result, an immunohistological staining of tissue section for pathological examination is obtained. Tissues can also be extracted, e.g., with urea and neutral detergent, for the liberation of hD54 protein for Western-blot or dot/slot assay (Jalkanen, M., et al., J. Cell. Biol. 707:976-985 (1985); Jalkanen, M., et al, J. Cell . Biol. 705:3087-3096 (1987)). In this technique, which is based on the use of cationic solid phases, quantitation of hD54 protein can be accomplished using isolated hD54 as a standard. This technique can also be applied to body fluids. With these samples, a molar concentration of hD54 protein will aid to set standard values of hD54 protein content for different body fluids, like serum, plasma, urine, spinal fluid, etc. The normal appearance of hD54 amounts can then be set using values from healthy individuals, which can be compared to those obtained from a test subject. Other antibody-based methods useful for detecting hD54 gene expression include immunoassays, such as the enzyme linked immunosorbent assay (ELISA) and the radioimmunoassay (RIA). For example, a monoclonal antibody can be used both as an immunoabsorbent and as an enzyme-labeled probe to detect and quantify the hD54 protein. The amount of hD54 protein present in the sample can be calculated by reference to the amount present in a standard preparation using a linear regression computer algorithm. Such an ELISA for detecting a tumor antigen is described in Iacobelli et al, Breast Cancer Research and Treatment 77:19-30 (1988). In another ELISA assay, two distinct monoclonal antibodies can be used to detect hD54 protein in a body fluid. In this assay, one of the antibodies is used as the immunoabsorbent and the other as the enzyme-labeled probe. The above techniques may be conducted essentially as a "one-step" or "two-step" assay. The "one-step" assay involves contacting hD54 protein with immobilized antibody and, without washing, contacting the mixture with the labeled antibody. The "two-step" assay involves washing before contacting the mixture with the labeled antibody. Other conventional methods may also be employed as suitable. It is usually desirable to immobilize one component of the assay system on a support, thereby allowing other components of the system to be brought into contact with the component and readily removed from the sample. Suitable enzyme labels include, for example, those from the oxidase group, which catalyze the production of hydrogen peroxide by reacting with substrate. Glucose oxidase is particularly preferred as it has good stability and its substrate (glucose) is readily available. Activity of an oxidase label may be assayed by measuring the concentration of hydrogen peroxide formed by the enzyme-labeled antibody/substrate reaction. Besides enzymes, other suitable labels include radioisotopes, such as iodine ( 125 1, 121 I), carbon ( 14 C), salphee ( 35 S), tritium ( 3 H), indium ( 112 In), and technetium ( 99m Tc), and fluorescent labels, such as fluorescein and rhodamine, and biotin. In addition to assaying hD54 protein levels in a biological sample obtained from an individual, hD54 protein can also be detected in vivo by imaging. Antibody labels or markers for in vivo imaging of hD54 protein include those detectable by X-radiography, NMR or ESR. For X-radiography, suitable labels include radioisotopes such as barium or caesium, which emit detectable radiation but are not overtly harmful to the subject. Suitable markers for NMR and ESR include those with a detectable characteristic spin, such as deuterium, which may be incorporated into the antibody by labeling of nutrients for the relevant hybridoma. An antibody or antibody fragment which has been labeled with an appropriate detectable imaging moiety, such as a radioisotope (for example, 131 I, 112 In, 99m Tc), a radio-opaque substance, or a material detectable by nuclear magnetic resonance, is introduced (for example, parenterally, subcutaneously or intraperitoneally) into the mammal to be examined for breast cancer. It will be understood in the art that the size of the subject and the imaging system used will determine the quantity of imaging moiety needed to produce diagnostic images. In the case of a radioisotope moiety, for a human subject, the quantity of radioactivity injected will normally range from about 5 to 20 millicuries of 99m Tc. The labeled antibody or antibody fragment will then preferentially accumulate at the location of cells which contain the protein. In vivo tumor imaging is described in S.W. Burchiel et al, Immunopharmacokinetics of Radiolabelled Antibodies and Their Fragments, in TUMOR IMAGING : THE RADIOCHEMICAL DETECTION OF CANCER (S.W. Burchiel and B.A. Rhodes, eds., Masson Publishing Inc. (1982)). Antibodies for use in the present invention can be raised against the intact hD54 protein or an antigenic polypeptide fragment thereof, which may presented together with a carrier protein, such as an albumin, to an animal system (such as rabbit or mouse) or, if it is long enough (at least about 25 amino acids), without a carrier. As used herein, the term "antibody" (Ab) or "monoclonal antibody" (Mab) is meant to include intact molecules as well as antibody fragments (such as, for example, Fab and F(ab') 2 fragments) which are capable of specifically binding to the hD54 protein. Fab and F(ab') 2 fragments lack the Fc fragment of intact antibody, clear more rapidly from the circulation, and may have less non-specific tissue binding of an intact antibody (Wahl et al, J. Nucl. Med. 24:316-325 (1983)). Thus, these fragments are preferred. The antibodies of the present invention may be prepared by any of a variety of methods. For example, cells expressing the hD54 protein or an antigenic fragment thereof can be administered to an animal in order to induce the production of sera containing polyclonal antibodies. In a preferred method, a preparation of hD54 is prepared and purified to render it substantially free of natural contaminants. Such a preparation is then introduced into an animal in order to produce polyclonal antisera of greater specific activity. In the most preferred method, the antibodies of the present invention are monoclonal antibodies (or hD54-binding fragments thereof). Such monoclonal antibodies can be prepared using hybridoma technology (Kohler et al, Nature 256:495 (1975); Kohler etal, Eur. J. Immunol. 6:511 (1976); Kohler etal, Eur. J. Immunol. 6:292 (1976); Hammerling etal., MONOCLONAL ANTIBODIES AND T- CELLHYBRIDOMAS, 563-681 (Elsevier, N.Y., 1981)). In general, such procedures involve immunizing an animal (preferably a mouse) with a hD54 antigen or, more preferably, with a cell expressing the antigen. Suitable cells can be recognized by their capacity to bind anti-hD54 antibody. Such cells may be cultured in any suitable tissue culture medium; however, it is preferable to culture cells in Earle's modified Eagle's medium supplemented with 10%> fetal bovine serum (inactivated at about 56 ° C), and supplemented with about 10 μg/1 of nonessential amino acids, about 1,000 U/ml of penicillin, and about 100 μg/ml of streptomycin. The splenocytes of such mice are extracted and fused with a suitable myeloma cell line. Any suitable myeloma cell line may be employed in accordance with the present invention; however, it is preferable to employ the parent myeloma cell line (SP 2 O), available from the American Type Culture Collection, Rockville, Maryland. After fusion, the resulting hybridoma cells are selectively maintained in HAT medium, and then cloned by limiting dilution as described by Wands et al., Gastro- enterology 50:225-232 (1981). The hybridoma cells obtained through such a selection are then assayed to identify clones which secrete antibodies capable of binding the hD54 antigen. It will be appreciated that Fab and F(ab') 2 and other fragments of the antibodies of the present invention may be used according to the methods disclosed herein. Such fragments are typically produced by proteolytic cleavage, using enzymes such as papain (to produce Fab fragments) or pepsin (to produce F(ab') 2 fragments). Alternatively, antigen binding fragments can be produced through the application of recombinant DNA technology or through synthetic chemistry. Where in vivo imaging is used to detect levels of hD54 protein in humans, it may be preferable to use "humanized" chimeric monoclonal antibodies. Such antibodies can be produced using genetic constructs derived from hybridoma cells producing the monoclonal antibodies described above. Methods for producing chimeric antibodies are known in the art. See, Morrison, Science 229:1202 (1985); Oi et al, BioTechniques 4:214 (1986); Cabilly et al, U.S. Patent No. 4,816,567; Taniguchi et al, EP 171496; Morrison et al, EP 173494; Neuberger et al, WO 8601533; Robinson et al., WO 8702671; Boulianne et al, Nature 572:643 (1984); Neuberger et al, Nature 574:268 (1985). Having generally described the invention, the same will be more readily understood through reference to the following examples which are provided by way of illustration and are not intended to be limiting. It will be appreciated to those skilled in the art that the invention can be performed within a wide range of equivalent parameters of composition, concentrations, modes of administration, and conditions without departing from the spirit or scope of the invention or any embodiment thereof. The disclosure of all references, patent applications and patents recited herein are hereby incorporated by reference. Examples Example 1: Characterization of D 52-like proteins D52-like proteins interact homo- and heteromerically within the yeast two- hybrid system In order to test whether D52-like proteins interact within the yeast two- hybrid system, the relevant coding sequences (or portions thereof) were subcloned into the yeast two-hybrid vectors pACT2 and/or pAS2-l, such that these sequences were in-frame with those encoding the GAL4 transcriptional activation domain (GAL4-AD), or the DNA-binding domain (GAL4-DB), respectively. Proteins fused with the GAL4-AD were referred to as interactors, whereas those fused with the GAL4-DB were referred to as baits. The D52-like proteins tested represent the human and mouse homologues of D52 (hD52 and mD52), hD53, and 3 hD54 isoforms (Figure 5). The existence of multiple hD54 isoforms was predicted from coding sequence differences identified in hD54 cDNAs, with hD54 sequences differing with respect to a region encoding a 20 amino acid insertion, ins2 (Figure 5). Whereas 2 hD54 cDNA clones contained the 60 bp sequence encoding ins2 (nucleotides 391-450 of SEQ ID NO:5), this was absent from another cDNA clone. A further variation was noted where a 71 bp deletion (nucleotides 380-450 of SEQ ID NO: 5) was predicted to remove ins2, plus an additional 4 residues from the translated sequence. This deletion was not produced in-frame, and a truncated product was predicted to result after 42 amino acids (Figure 5). We refer to the 3 isomeric forms of hD54 thus predicted as hD54+ins2, hD54-ins2, and hD54t. Before proceeding with a testing of interactions, D52-like baits and interactors were individually tested for their inability to activate Y190 reporter gene expression. Y190 yeast strains which had been transfected with individual constructs were grown on either solid SDΛTrp media (for baits) or SD/-Leu media (for interactors) incorporating 0.07 M potassium phosphate pH 7, and 40 μg/ml 5- bromo-4-chloro-3-indoyl-β-D-galactopyranoside (X-gal). After 4 days incubation at 30 °C, colony phenotypes were compared with that of Y 190 yeast transfected with the corresponding vector as a negative control. Excepting the case of Y 190 yeast transfected with the hD54t bait, a white colony phenotype was obtained for all Y190 strains tested, indicating that these D52-like baits and interactors were unable to activate the Y 190 lacZ reporter gene. However, Y 190 yeast transfected with the hD54t bait gave a blue colony phenotype after 2 days incubation at 30°C on solid SD/-Trp media containing X-gal, indicating that this hD54 isoform was unsuitable for further use in the yeast two-hybrid system. For direct testing of interactions between D52-like fusion proteins, each bait plasmid (pAS2-lhD52, pAS2-lmD52, pAS2-lhD53, pAS2-lhD54+ins2, pAS2-lhD54-ins2, and pAS2-l as a negative control), was paired with each interactor plasmid (pAD-GAL4hD52, pACT2mD52 (M63) , pACT2hD53, pACT2hD54+ins2, pACT2hD54-ins2, and pACT2 as a negative control), and co- transfected into Y190. Interactions between baits and interactors were assessed by qualitatively and/or quantitatively determining H7S5 and/or lacZ reporter gene activity in Yl 90 co-transfectants. All D52-like fusion proteins tested were found to be capable of both homo- and heteromer formation in the yeast two-hybrid system (Table 1). However, the results of both qualitative and quantitative β- galactosidase assays indicated that interactions between different pairs of D52-like fusion proteins occurred with different strengths. In Y190 co-transfectants bearing hD53-encoding constructs, the highest β-galactosidase activity level was obtained for the interaction between hD53 fusion proteins (Table 1), indicating that homomeric interactions were preferred. However, in Yl 90 co-transfectants bearing mD52- or hD52-encoding constructs, homomeric interactions were indicated to be significantly weaker than heteromeric interactions between D52 and hD53 fusion proteins (Table 1 ). In the cases of Yl 90 co-transfectants bearing hD54+ins2 or hD54-ins2 constructs, the highest levels of β-galactosidase activity were also noted for heteromeric interactions with hD53 fusion proteins (Table 1). Interactions between D 52-like proteins occur via their coiled-coil domains In order to test whether the interactions observed between D52-like proteins occurred via their coiled-coil domains as predicted, we employed two bait constructs, pAS2-lmD52 (1 . 95) and pAS2-lmD52 (95.185) These encode fusion proteins between the GAL4-DB and the N-terminal half of mD52 (which includes the predicted coiled-coil domain at residues 29-71 of SEQ ID NO 4), or the C- terminal half of mD52, respectively These bait constructs, or pAS2-lmD52 as a positive control, were paired with the interactor plasmid pACT2hD53, or pACT2 as a negative control, and co-transfected into Y 190 cells, and interactions were qualitatively and/or quantitatively assessed by determining HIS3 and lacZ reporter gene activity (Table 2) Similar levels of β-galactosidase activity were obtained in Y190 cells co-transfected with the hD53 interactor and full-length mD52 or mD52 α . 95) baits, whereas negligible β-galactosidase activity was detected in Y 190 co-transfectants bearing the hD53 interactor and mD52 (95 . 185) bait (Table 2). This indicated that the first 95 amino acids of mD52, which include the coiled- coil domain, were responsible for mediating the interaction observed between the mD52 bait and hD53 (Tables 1 and 2). hD52 and hD 53 proteins were identified as potential interactors for hD52 and hD53 baits using yeast two-hybrid screening We chose to construct and screen an expression library using the same human breast carcinoma from which the hD52, hD53 and hD54 cDNAs had been isolated (Byrne, J.A., et al, Cancer Res. 55:2896-2903 (1995); and Byrne, J.A., et al, Genomics 55:523-532 (1996)). In this way, interacting proteins identified through library screening would be more likely to be co-expressed with D52-like proteins, and thus to represent biological partners for these proteins (Allen J.B., et al, Trends Biochem. Sci., 20:511-516 (1995)). Screening approximately 772,200 colony forming units (cfu) of the breast carcinoma cDNA expression library in Y190 cells using the full-length hD53 bait resulted in the identification of 8 Y190 colonies which were His+ and lacZ+. Of these, 6 colonies contained pAD-GAL4 constructs encoding hD53, and one colony contained a pAD-GAL4 construct encoding hD52 (pAD-GAL4hD52) (Table 3). The remaining colony contained a pAD-GAL4 construct encoding suilisol (GenBank accession no. L26247), but retransfection of Y190 cells with this construct and the hD53 bait did not reproduce the His+ lacZ+ phenotype. All hD53 and hD52 cDNAs included sequence encoding the entire predicted coiled- coil domain (Table 3). Screening approximately 1,350,000 cfu of the same expression library in Yl 90 cells using the full-length hD52 bait resulted in the identification of only one His+lacZ+ Y190 colony. This contained a pAD-GAL4 construct encoding/te-7 (GenBank accession no. M84711), for which the interaction with the hD53 bait was not reproducible. Since this approach did not identify any reproducible interactor for the hD52 bait, we elected to perform a more sensitive screening in Hf7c cells. The Hf7c H1S3 reporter is less "leaky" than the Y190 HIS3 reporter (Feilotter, H.E., et al, Nucleic Acids Res. 22: 1502-1503 (1994) and; Durfee, T., et al, Genes Dev. 7:555-569 (1993)), and t e HIS3 competitor 3-amino-l, 2, 4- triazole is therefore not required to be added to selective media to suppress a basal level OΪHIS3 expression (Feilotter, H.E., et al. , Nucleic Acids Res. 22: 1502- 1503 (1994)). Thus, weaker interactions with bait proteins are more likely to be detected (Allen J.B., et al, Trends Biochem. Sci., 20:511-516 (1995)). In addition, to increase the chance of identifying interactors binding D52 regions other than the coiled-coil domain, we elected to use both full-length hD52 and mD52 (95 . lg5) baits. Screening approximately 44,000 cfu of the breast carcinoma cDNA expression library in Hf7c cells resulted in a total of 10 His+ colonies. Of these, single colonies contained pAD-GAL4 constructs encoding hD53 and hD52 interactors with complete coiled-coil domains (Table 3). The remaining colonies contained pAD-GAL4 constructs encoding eukaryotic initiation factor 4AII (DNA Database of Japan accession no. D30655), histidyl t-RNA synthetase (EMBL accession no. Zl 1518), NADH dehydrogenase 3 (identified twice, EMBL accession no. X62996), collagen type 1 -2 chain (GenBank accession no. J03464), RING10 proteasome subunit (GenBank accession no. X62598) and novel cDNAs of 10 kb (GenBank accession no. AA036831) and 1.7 kb (no database match). However, retransfection of Hf7c with these interactors and the individual D52 baits used in screening did not reproduce a His+ phenotype. Identification of a novel hD53 isoform using yeast two-hybrid screening Of the 7 hD53 cDNAs identified in this study using D52-like baits, the sequence of one (+5) differed significantly from those of the remaining 6 hD53 cDNAs, and from previously identified D53 cDNA sequences (Byrne, J.A., etal, Genomics 55:523-532 (1996)). The most 5' 59 bp of the +5 cDNA could not be aligned with any other 7)55 sequence, and predicted a 20 amino acid stretch which showed no similarity to hD53 (Figure 2). However, the coding sequences and reading frames of +5 and hD53 subsequently became identical for 365 bp, at which point a 100 bp deletion was noted in the +5 cDNA sequence with respect to hD53 (nts 567-666, GenBank accession no. U44427). Since the deletion does not occur in-frame, a truncated product is predicted to result (Figure 2). The +5 cDNA does not appear to be full-length, since there is no Met residue in a favorable context for translation initiation within the novel sequence (Figure 2, SEQ ID NO:l). Thus while it is difficult to predict the size of the novel hD53 isoform, it is predicted to be greater than 144 amino acids in length. Glutathione S-transferase (GST) pull-down assays indicate homo- and heteromeric interactions between recombinant GST-mD52 protein and in vitro- translated D 52-like proteins In order to examine whether D52-like proteins are able to interact homo- and heteromerically in vitro as well as in vivo, we analyzed binding between GST- tagged mD52 protein and in v/ ' tr -translated D52-like proteins using a GST pull- -down assay system. In vitro translation oϊmD52 and hD52 coding sequences gave rise to single 28 kDa 35 S-labelled proteins, whereas in vitro translation of the hD54-ins2 coding sequence gave rise to a 31 kDa 35 S-labelled protein (Figure 6A). While larger than might be predicted from amino acid sequence data alone, these protein sizes are in agreement with that reported for CSPP28 (Parente (Jr), J.A., et al, J. Biol. Chem. 277:20096-20101 (1996)). Recombinant GST-mD52, or GST alone, were produced in the BL21 E. coli strain, and soluble post-induction extracts were incubated with glutathione-agarose. The subsequently bound GST- mD52 or GST was then incubated with in-vitro translated proteins, and a large excess of soluble BL21 extract as a complex binding competitor. Following washing of matrices and the elution of bound material, the binding characteristics of in v/ ' tro-translated D52-like proteins to GST (Figures 6B and 6C) or GST- mD52 (Figures 6D and 6E) could be compared. Autoradiographs (Figure 6D and 6E) of Coomassie Brilliant Blue-stained gels (Figure 6B and 6D) indicated that 35 S-labelled D52-like proteins were only retained on matrices to which GST-mD52 was bound. In v/ ' tro-translated proteins were not retained on glutathione-agarose to which GST had been bound, indicating that 35 S-labelled D52-like proteins were unable to bind to either GST or glutathione-agarose. Discussion The hypothesis that D52-like proteins are capable of interacting both homo- and heteromerically was initially advanced on the basis of several lines of evidence (Byrne, J.A., et al., Genomics 55:523-532 (1996)). Similar coiled-coil domains were predicted in both hD52 and hD53 proteins, and the corresponding genes were observed to be either co- or independently expressed in human cell lines. Moreover, examples of similar regulation of hD52 and hD53 transcript levels in both breast carcinoma and leukemic cell lines suggested the existence of a functional relationship between hD52 and hD53 (Byrne, J.A., et al, Genomics 55:523-532 (1996)). The present study has permitted both the confirmation of this hypothesis, and its extension to include a third member of the D52 protein family, hD54, in that D52-like proteins were found to interact in homo- and heteromeric fashions both in vivo (Tables 1 and 2) and in vitro (Figures 6A-6E). Using the yeast two-hybrid system, we were able to demonstrate interactions between all D52-like fusion proteins tested which, in most cases, were independent of whether a given D52-like protein was present as a bait or an interactor (Table 1). Similarly, screening a human breast carcinoma expression library using both hD53 and hD52 baits identified both homo- and heteromeric interactions between these proteins (Table 3) Interactions between mD52 and hD53 fusion proteins were found to be mediated via mD52 residues 1-95, which include the predicted coiled-coil domain at Glu 29 -Leu 71 (Table 2) Indications that hD52 and hD53 coiled-coil domains were also mediating homo- and heteromeric interactions between these proteins derive from the results of yeast two-hybrid screenings, where all hD52 and hD53 interactors identified contained sequences encoding entire coiled-coil domains (Table 3) Results from both direct testing of interactions between D52-like fusion proteins and yeast two-hybrid screenings have indicated that not all interactions between D52-like proteins occur with the same strengths In particular, homomeric interactions were indicated to be preferred by the hD53 bait (Tables 1 and 3), whereas heteromeric interactions with hD53 fusion proteins were preferred by the D52 and hD54 proteins tested (Table 1 ) However, a comparison of interactions between D52-like proteins and the hD54 isoforms hD54+ins2 or hD54-ins2 indicated that the presence or absence of ins2 did not significantly affect the interaction preferences of hD54 baits or interactors (Table 1 ) Thus, the presence or absence of ins2 24 amino acids C-terminal of the hD54 coiled-coil domain does not appear to obviously affect this domain's function The significance of ins2 in hD54 proteins is however unclear, as no homology can be identified between the 20 amino acids comprising ins2, and sequence regions of other known proteins. The cloning of an alternatively-spliced form of hD53 during a yeast two- hybrid screening using the hD53 bait has also provided further evidence that multiple protein isoforms may be produced from D52-like genes (Proux, V , etal, J. Biol Chem. 277:30790-30797 (1996)) The +5 hD53 cDNA identified in the present study predicts a C-terminally truncated hD53 protein as a result of a 100 bp out-of-frame deletion removing hD53 nts 567-666 (GenBank accession no U44427) The resulting truncation occurs three residues after Met 128 , which represents the first residue of an alternatively-spliced 13 amino acid region (Met 128 -Ala 140 ) referred to as ιns3 (Figure 2) A 23 amino acid ins3-like sequence is also predicted in a quail D52 homologue, RIO (Proux, V , et al, J. Biol Chem. 277:30790-30797 (1996)) We had previously sequenced a partial hD53 cDNA (clone 83289, GenBank accession nos T68402 and U44429) isolated by the IMAGE consortium (Lennon G , et al, Genomics 55:151-152 (1996)) which contained the same 100 bp deletion now noted in the +5 cDNA (Byrne, J.A , et al, Genomics 55:523-532 (1996)) As this deletion was only observed in a single cDNA at this time, we could not exclude the possibility that it had arisen through a cloning artifact However, 4 additional expressed sequence tags (ESTs) now also show identical 100 bp deletions (GenBank accession nos AA055718, AA066421, Wl 1611, and W14257), and another EST (GenBank accession no W69680) shows a smaller deletion of 61 bp (hD53 nts 606-666, GenBank accession no U44427) which predicts a similar truncation occurring three residues after Met 141 , immediately after ins3 (Figure 2) That alternative splicing mechanisms appear to regulate the presence or absence of the C-terminal portion of hD53 (and particularly, the presence or absence of ins3) suggests that these regions have roles in modulating D53 function While single putative D52 homologues have thus far been indicated in C. elegans (EMBL Accession No Z68105; Wilson, R , et al, Nature 5(55:32-38 (1994)), andZ melanogaster (GenBank Accession Nos AA263893, AA390326, and AA392910), three human D52-like genes have been identified, and analyses of mammalian expressed sequence tags identify sequences (GenBank Accession Nos W50222, W49042 and AA 130196) which predict the existence of additional mammalian D52-like genes Since RNAs deriving from those D52-like genes thus far cloned appear to be alternatively spliced (Proux, V , et al, J. Biol. Chem. 277:30790-30797 (1996)), a significant number of D52-like proteins may thus exist This, combined with the fact that in the present study, each D52-like protein tested could interact with every other D52-like protein examined, indicates a potentially rich array of interactions between D52-like proteins, depending up the number of individual D52-like genes and isoforms expressed in a particular cell type. However, despite extensive screening of a human breast carcinoma yeast two-hybrid expression library in both Yl 90 and Hf7c yeast strains using different full-length and/or truncated D52-like baits, no other partners were identified for D52-like proteins. While nonetheless indicating that interactions between D52- like proteins are highly specific, additional factors may have contributed towards this result. Firstly, technical limitations associated with the yeast two-hybrid system (Allen J.B., et al, Trends Biochem. Sci., 20:511-516 (1995)) may have prevented the demonstration of interactions between D52-like baits and other interactor types. Secondly, it may be that interactions between D52-like proteins and other partners are too weak and/or transient to be detected using the two- hybrid system. In the present study, screening sensitivity was maximized by performing two-hybrid screenings in both Hf7c and Y190 strains with the hD52 bait. That the screening in Hf7c cells was more sensitive was indicated by the fact that interactions between the hD52 bait and hD52 or hD53 interactors were only identified in Hf7c cells, despite the fact that a significantly greater proportion of the breast carcinoma library was screened in Y 190 cells. Similarly, the number of false-positives obtained in Hf7c cells compared with that obtained in Y 190 cells also attests to the sensitivity of the Hf7c HI S3 reporter (Feilotter, H.E., et al, Nucleic Acids Res. 22:1502-1503 (1994)). However, since two-hybrid systems have been reported to be inherently more sensitive than other methods of identifying protein-protein interactions (Allen J.B ., et al, Trends Biochem. Sci., 20:511-516 (1995)), proteins which interact either more weakly and/or transiently with D52-like proteins than D52-like proteins themselves may be difficult to identify using other methodologies. Finally, it is possible that additional partners exist for D52-like proteins in other tissues, but that these are either of low abundance, or not expressed, in breast carcinoma. The CSPP28 and R10 molecules, which represent D52 homologues in rabbit and quail, respectively, have been implicated in calcium-mediated signal transduction processes (Parente (Jr), J.A., etal, J. Biol. Chem. 277:20096-20101 (1996)) and the control of cellular proliferation (Proux, V., et al, J. Biol. Chem. 277 30790-30797 (1996)) The interactions between D52-lιke molecules demonstrated in the present study may be integral to the roles of D52-lιke proteins in these cellular processes, Proux, V , et al , J Biol Chem 271 30790-30797 ( 1996) having also demonstrated homomeric interactions between epitope-tagged and untagged R10 proteins The functional importance of interactions between D52-hke molecules is further supported by the prediction that increased expression of D52-hke genes, such as reported for hD52 in a proportion of human breast carcinomas (Byrne, J A , etal , Cancer Res 55 2896-2903 (1995)), might be predicted to increase cellular concentrations of the corresponding protein, and thus the proportion of that protein found in homo- and/or heteromeric complexes Thus, if increased hD52 gene expression promotes breast cancer cell proliferation, it might be predicted that the (more) active form of hD52 in this process is that which is bound to hD52, or other D52-hke proteins Yeast strains and media Yeast cultures were grown at 30 ° C in standard liquid or solid media, based upon either rich YPD media (2% bacto-peptone, 1%> yeast extract, 2%> dextrose), or minimal SD medium (0 67% yeast nitrogen base without amino acids, 2% dextrose, with appropriate amino acid supplements) The Saccharomyces cerevisiae strain Yl 90 (genotype MATa, ura3-52, hιs2-200, lys2-801, ade2-101, trpl-901, leu2-3, 112, gal4Δ, gal80Δ, cyh r 2, LYS2 GALl UA:r HIS3 TATA -HIS3, URA3 GAL1 UAS -GAL1 TATA -lacZ) (Clontech) was used for direct testing of interactions, whereas Y190 and Hf7c strains (Hf7c genotype MATa, ura3-52, hιs3-200, lys2-801, ade2-101, trpl-901, leu2-3, 112, gal4-542, gal80-538, LYS2 GAL1 UAS -GAL1 TATA -HIS3, URA3 (GAL1 17mers)3-CyCl TATA -lacZ) were used for expression library screenings Plasmid constructions for the yeast two-hybrid system Constructs for use in the yeast two-hybrid system were made using the pAS2-l and pACT2 vectors (Clontech). The pAS2-l vector contains the selectable marker TRP1, and permits the expression of fusion proteins with the GAL4 (1 . 47) DNA-binding domain, whereas pACT2 contains the selectable marker LEU2, and permits the expression of fusion proteins with the GAL4 (768 . 881) activation domain. The following pAS2-l and pACT2 constructs were made by subcloning .Z ) 52-like coding sequences (or portions thereof) in-frame using internal restriction sites, and in some cases, those of the original pBS SK- multiple cloning sites: pAS2-lhD52, a Pst I-Nsi I fragment comprising nts 64-719 oϊhD52 and thus including the entire hD52 coding region (Byrne, J. A., et al, Cancer Res. 55:2896-2903 (1995)), was subcloned into the Pst I site of pAS2-l; pAS2- lmD52, a Pst I-Pst I fragment including nts 1-832 oϊmD52 and thus the entire mD52 coding region (Byrne, J.A., et al, Genomics 55:523-532 (1996)), was subcloned into the Pst I site of pAS2-l; pAS2-lhD53, an Nco I-Sal I fragment including nts 180-1347 of hD53, and thus the entire hD53 coding region (Byrne, J.A., etal, Genomics 55:523-532 (1996)), was subcloned into the Nco I and Sal I sites of pAS2-l; pAS2-lmD52 (1 . 95) , a Pst I-Nsi I fragment including nts 1-306 of mD52, and thus the region encoding amino acids 1-95 of mD52 was subcloned into the Pst I site of pAS2- 1 ; pAS2- 1 mD52 (95 . 185) , a Nsi I-Nsi I fragment including nts 307-787 of mD52, and thus the region encoding amino acids 95-185 of mD52 was subcloned into the Pst I site of pAS2-l; pACT2mD52 (1 _ 163) , an EcoR I-EcoR I fragment including nts 1 -507 of mD52, and thus the region encoding amino acids 1-163 ofmD52 was subcloned into the EcoR I site of pACT2; and pACT2hD53, an Nco I-Xho I fragment including nts 180-1347 oϊhD53, and thus the entire hD53 coding region was subcloned into the Nco I and Xho I sites of pACT2. In the case of the hD52 cDNA (Byrne, J.A., et al, Cancer Res. 55:2896-2903 (1995)), suitable restriction sites for use with the pACT2 vector were absent, and thus a pAD-GAL4hD52 plasmid isolated through yeast two-hybrid screening (see below, Table 1) was used for the direct testing of interactions. In the case of hD54 cDNAs encoding the 3 hD54 isoforms hD54+ins2, hD54-ins2 and hD54t (GenBank accession no. AF004430), suitable internal restriction sites for both pAS2-l and pACT2 vectors were absent, and thus coding sequences were PCR- amplified using the primers 5'-CG CAT GCC ATG GAC TCC GCC GGC-3 ' (SEQ ID NO: 103) and 5'-TCC CCC GGG GGA TTA GAA AGG TGC GGG ATC-3 ' (SEQ ID NO: 104). For hD54 cDNAs encoding all 3 hD54 isoforms, these PCR primers permitted amplification of sequences including full-length hD54 coding regions, the conversion of a 5 ' cryptic Nco I site to a full Nco I site, and the introduction of a 3' Sma I site. Resulting PCR products were digested with Nco I and Sma I, and subcloned into the corresponding restriction sites of pACT2 and/or pAS2-l vectors. This approach resulted inthepAS2-lhD54+ins2, pAS2-lhD54-ins9, pAS2-lhD54t, pACT2hD54+ins2, pACT2hD54-ins2 constructs. The reading frame of each fusion protein between GAL4 and D52-like sequences was verified by automated sequencing (see below). Expression cDNA library construction A human breast carcinoma cDN A library was constructed in the HybriZAP vector using reagents and instructions supplied by the manufacturer (Stratagene). This vector permits the construction of λ bacteriophage cDNA libraries which can be converted to plasmid libraries in the pAD-GAL4 vector by in vivo excision. The pAD-GAL4 vector contains the selectable LEU marker and permits the expression of GAL4 (761 . 8gl) activation domain fusion proteins. Briefly, 5 μg polyA± RNA from a primary infiltrating ductal breast carcinoma (Byrne, J.A., et al, Cancer Res. 55:2896-2903 (1995)) was primed using an oligodT linker-primer incorporating a Xho I site, and reverse-transcribed using MMLV-RT. EcoR I adaptors were ligated and the resulting Xho I-digested inserts were ligated into prepared HybriZAP vector arms This resulted in approximately 5 x 10 6 plaque forming units (pfu) which were amplified once on an XL1 Blue M_RF' host. An aliquot of the λ bacteriophage library (5 x 10 9 pfu) was rescued using in vivo excision in the form of pAD-GAL4 phagemids in a SOLR host, according to the manufacturer's instructions (Stratagene). Plasmid DNA for library screenings was directly isolated from approximately 50 x 10 6 cfu grown on 128 large LB agar plates incorporating 100 μg/ml ampicillin, and purified using Qiagen 500 columns. Over 90%) of pAD-GAL4 plasmids were found to contain inserts, with the average insert length being 1.1 kb. Yeast two-hybrid system For the direct testing of interactions, paired baits (pAS2- 1 constructs) and interactors (pACT2 or pAD-GAL4 constructs) were transfected into the Y190 yeast strain according to the supplier's instructions (Clontech), with co- transfectants being initially selected on solid SD media lacking Trp and Leu. Interactions between baits and interactors were assessed by qualitatively and/or quantitatively determining HIS3 and lacZ reporter gene activity in Y190 co- transfectants. Reporter gene activities were assessed qualitatively by observing the growth and color development of Y 190 co-transfectants on solid SD media lacking His, Trp and Leu (SD/-His-Trp-Leu), and incorporating 0.07 M potassium phosphate pH 7, 35 mM 3 -AT, and 40 μg/ml X-gal. For quantitative assessment of interactions, β-galactosidase activity was measured using the substrate o- nitrophenyl β-D-galactopyranoside (ONPG) in liquid cultures (SD/-His-Trp-Leu + 35 mM 3-AT) of Y190 co-transfectants. As a positive control for each assay, and to permit the comparison of results obtained in different assays, β- galactosidase activity was also measured in liquid cultures (SDΛLeu) of Y 190 transfected with the GAL4-encoding construct pCLl (Clontech). For both qualitative and quantitative assays, negative controls were supplied by Y190 co- transfectants in which each bait or interactor had been paired with the opposing empty vector. Yeast two-hybrid screening Bait (pAS2-lhD53, or pAS2-lhD52 with or without pAS2-lmD52 (95 . 185) ) and human breast carcinoma pAD-GAL4 library plasmids were transfected either sequentially or simultaneously into Y190 or Hf7c strains. Transformants were plated onto solid SD/-His-Trp-Leu (incorporating 35 mM 3 -AT in the case of Y190 transformants) and incubated for up to 14 days at 30 °C. After 3 initial days of growth, plates were inspected daily, and His+ colonies were transferred to SD/- His-Trp-Leu + 0.07 M potassium phosphate pH 7 + 40 μg/ml X-gal plates which incorporated 35 mM 3 -AT in the case of Y 190 co-transformants. Colonies which remained His+, and in the case of Yl 90 co-transformants, were also lacZ±, were re-streaked onto fresh plates to check that all colonies were of uniform phenotype. After 6 days incubation at 30 °C, yeast colonies were directly harvested, and plasmid DNA was isolated and used to transfect XLl Blue. Mini-preparations of plasmid DNA were performed for at least 5 XLl Blue colonies per transfection, with the results of restriction digests differentiating potential interactors from bait plasmids. Potential interactors were identified by DNA sequencing (see below) and re-transfected into the yeast strain used in library screening, with the relevant bait, or the pAS2-l vector as a negative control. Phenotypes of resulting co- transfectants were assayed quantitatively and/or qualitatively as described above. Where re-transfection of an interactor did not reproduce the phenotype originally observed during library screening, the interactor was termed a "false-positive". Plasmid constructions for in vitro transcription/translation and GST-pull down assays Constructs for in vitro transcription/translation were made using the pTLl vector, a derivative of pSG5 (Green, S., etal, Nucleic Acids Res. 16:369 (1988)), which permits in vitro transcription from the T7 promoter. The following pTLl constructs were made by subcloning/_Z)52-like coding sequences with flanking 5 '- and 3 '-UTR regions using internal restriction sites, and in some cases, those of the original pBS SK- multiple cloning sites: pTLlhD52, a BamH I-Bgl II fragment including nts 25-972 of hD52 was subcloned into the BamH I site of pTLl; pTLlmD52, a Pst I fragment including nts 1 -832 oϊmD52 was subcloned into the Pst I site of pTLl; and pTLlhD54-ins2, a Xho I-Pst I fragment including nts 51- 662 ϊhD54-ins2 was subcloned into the Xho I and Pst I sites of pTLl . All pTLl constructs were verified using automated sequencing (see below). A construct allowing prokaryotic expression of N-terminally GST-tagged mD52 protein was made using the pGEX3X-6His vector, representing a modified form of pGEX3X (Pharmacia) which also permits the incorporation of a C-terminal 6-histidine tag. Nhe I and Xba I restriction sites were introduced into the mD52 coding sequence using site-directed mutagenesis (Kunkel, T. A., et al, Methods Enzymol 754:367- 382 (1987) and; Ausubel, F.M., et al, Current Protocols in Molecular Biology Vol. I (1997)) and the oligonucleotide primers 5 '-G CGG GAG CGA GGT GGC GCT AGC ATG GAC CGC GGC GAG C-3 ' (SEQ ID NO: 105) and 5 '-G ATG ACA GAG AGC CCC TCT AGA GCC GAC CTG TGT CCT G-3 ' (SEQ ID NO: 106), which permitted subcloning of the full-length mD52 coding sequence. Prior to subcloning into pGEX3X-6His, the mD52 insert subjected to mutagenesis was verified by automated sequencing (see below), as was the reading frame between sequences encoding GST and mD52 in the subsequently-generated pGEX3XrnD52-6His construct. In vitro transcription/translation Coupled in vitro transcription and translation of D52-like proteins was performed using the TNT T7 wheat germ lysate system (Promega Corp.) according to the manufacturer's instructions. Briefly, 0.5 μg linearized plasmid DNA was included in a 25 μl reaction volume with 2 μl translation grade 35 S- Methionine (Amersham Corp.) and incubated at 30° C for 90 min. Protein product sizes were verified by electrophoresing 2.5 μl of each reaction through a 10% denaturing polyacrylamide gel which was then fixed, dried, and exposed to autoradiographic film (BioMax, Kodak) for 3 days at -80 °C. GST-pull down assays Recombinant GST-mD52, and GST protein, were produced in the BL21 E. coli strain following the induction of log-phase cultures with 250 μg/ml IPTG for 2 h at 37° C. Proteins were isolated by incubating E. coli samples in isotonic lysis buffer (10 mM potassium phosphate pH 8.0, 140 mM KC1, 3 mM MgCl 2 , 1 mM DTT, 0.5% Nonidet P-40, 0.5 mM PMSF) for 15 min on wet ice, followed by brief sonication. Protein product sizes were verified by electrophoresing pre- and post-induction protein samples on \0% SDS-polyacrylamide gels, followed by Coomassie Brilliant Blue staining. Post-induction protein extracts were incubated with glutathione-agarose (Sigma) which had been previously saturated in 0.5%) (w/v) BSA (fraction V, Boehringer-Mannheim). Recombinant proteins (2-5 μg) bound to 30 μl glutathione agarose were then incubated with 7 μl of each in vitro translation reaction, and 2.6 mg soluble BL21 protein extract, prepared as described in Ausubel, F.M., etal, Current Protocols in Molecular Biology Vol. 3 (1996), for 2 h at 4° C. Matrixes were washed 3 times with 1 ml cold buffer (50 mM potassium phosphate pH 7.5, 150 mM KC1, 10 mM MgCl 2 , 10% (v/v) glycerol, 1% Triton X- 100, 0.5 mM PMSF), and bound proteins were eluted in 12 μl SDS-loading buffer (50 mM Tris pH 6.8, 2% (w/v) SDS, 10% (v/v) glycerol, 10% (v/v) 2-mercaptoethanol) by boiling for 5 min. Eluted proteins (6 μl) were separated on 10%> SDS-polyacrylamide gels, which were stained with Coomassie Brilliant Blue, dried, and exposed to autoradiographic film (BioMax, Kodak) for 10 days at -80° C. DNA Sequencing Mini-preparations of plasmid DNA were further purified by NaCI and polyethyleneglycol 6000 precipitation, and sequenced with Taq polymerase and dye-labeled ddNTPs for detection on an Applied Biosystems 373A automated sequencer. The oligonucleotide primers 5 '-TCATCGGAAGAGAGTAG-3 ' (SEQ ID NO: 107) (for pAS2-l constructs) and 5 '-TACCACTACAATGGATG-3 ' (SEQ ID NO: 108) (for pACT2 or pAD-GAL4 constructs) were used to permit sequencing of junctions between GAL4 and D52-like sequences. The T7 universal primer was used to determine 3 ' insert sequences of pAD-GAL4 constructs, and to verify the orientations of inserts in pTL 1 constructs. Complete insert sequences of pAD-GAL4 constructs were verified when required using internal hD52 or hD53 primers, and internal mD52 primers were used to verify the mD52 coding sequence subjected to site-directed mutagenesis, and the subsequently-derived ρGEX3XmD52-6His construct. Sequence Analyses Searches of nucleotide databases (updated daily) were performed using BLASTN and TBLASTN programs (Altschul, S.F., etal, J. Mol. Biol. 275:403- 410 (1990)). Multiple amino acid sequences were aligned using CLUSTAL (Thompson, J.D., et al, Nucleic Acids Res. 22:4673-4680 (1994)), with coiled- coil domains being predicted using Pepcoil (Lupas, A., et al, Science 252: 1162- 1164 (1991)). Example 2: Identification of mD53 The mD53 cDNA was isolated from an embryonic stem cell cDNA library using an 842 bp hD53 cDNA as a probe (Byrne, J.A., et al, Genomics 55:523- 532 (1996)). The 1307 bp mD53 cDNA (SEQ ID NO:3) includes a 615 bp coding region which predicts a 204 amino acid protein (SEQ ID NO: 4). The hD53 and mD53 proteins are predicted to be 91% identical/93% conserved, and as such are more highly conserved than the majority of orthologous mouse and human proteins (Makalowski, W., et al, Genome Res. 5:846-857 (1996)). In situ chromosomal mapping of the mD53 locus was performed, in order to determine whether the human and mouse loci are syntenically conserved. We elected to use a radioactively-labeled mD53 cDNA for this purpose, because of the greater sensitivity afforded by this labeling technique for shorter DNA probes. The mD53 cDNA was tritium labeled by nick-translation to a specific activity of 1 x 10 8 dpm/μg, and then hybridized to metaphase spreads at a final concentration of 100 ng/ml hybridization solution, as previously described (Mattei, M. G , et al. , Hum. Genet. (59:268-271 (1985)). This approach identified a single mD53 locus at the 10A4-10B2 region of the murine genome (Figure 7). This region is within a larger syntenic group spanning 27-33 cM on the mouse chromosome 10 genetic map where the corresponding human loci have been localized to human chromosome 6q (Lyon, M.F., etal, Mouse Genome 95:29-77 (1997); and Taylor, B.A., et al, Mamm. Genome tf:S190-S200 (1996)). Since the hD53 gene has been previously mapped to human chromosome 6q22-q23 using the same method (Byrne, J.A., et al, Genomics 55:523-532 (1996)), the human and mouse D53 loci appear to be syntenically conserved. The mammalian D52 gene family is thus emerging as being represented by genes found on different chromosomes (Byrne, J.A., etal, Genomics 55:523-532 (1996); and Byrne, J.A., etal, Cancer Res. 55:2896-2903 (1995)), Mourseetα/., manuscript in preparation) whose loci are syntenically conserved between the human and mouse. The existence of multiple D52-like genes in mouse and human compared with a single D52-like gene in Caenorhabditis elegans (Byrne, J A , et al. , Genomics 55:523-532 (1996)) indicates that the former arose from a common ancestor through gene duplication events Thus, syntenic conservation of D52- hke loci between human and mouse indicates that both the derivation of D52-like genes and their dispersal over different chromosomes predate the evolutionary separation of primates and rodents some 80 million years ago (Byrne, J A , etal, Genomics 55:523-532 (1996)) Example 3: Identification ofhD54 The present example outlines the identification of a novel human gene hD54, which represents a third D52 gene family member In situ mapping placed the hD54 gene on human chromosome 20ql3 2ql3 3, a localization distinct from those of both hD52 and hD53 genes The identification of hD54 cDNAs predicting 3 isomeric forms of hD54 suggested that alternatively- spliced transcripts may be produced from the 3 D52-like genes RT-PCR amplification of D52-like transcripts from developing and adult rat tissues was performed to investigate coding sequence heterogeneity within D52-like transcripts Direct sequencing of PCR products, and analyses of the expressed sequence tag divisions of nucleotide databases, indicated that alternatively- spliced transcripts predicting multiple protein isoforms are produced from all 3 D52-like genes Differential regulation of the use of alternative coding sequence regions was indicated, with particular alternative splicing events being regulated in tissue-specific and temporal fashions Isolation of human D54 cDNAs A cDNA 792554 (GenBank Accession No H39077), whose translated 5'- EST sequence showed 41 3% identity with amino acids 111-155 of hD52, and 62 3%) identity with amino acids 129-180 of hD53, was obtained (Genome Systems Inc , St Louis, MO), and its insert sequenced on both strands An open reading frame extending from the 5 '-end was predicted to encode 67 amino acids, the sequence of which could be aligned with C-terminal portions of hD52 and hD53 (Figure 8) The remainder of the nucleotide sequence represented a 1596 bp 3 ' -UTR, including an AATAAA polyadenylation signal Since 792554 was thus likely a partial-length cDNA, a breast carcinoma cDNA library was screened with the most 5 ' 193 bp of the 192334 cDNA insert in order to isolate full-length cDNAs Five cDNAs thus identified showed additional sequences at their 5 ' ends with respect to the 192334 sequence, and the insert of one, 7/77, was sequenced on both strands The presence of an ATG codon in a favourable context for translation initiation preceded by a stop codon indicated that the Hll cDNA consisted of a 76 bp 5'-UTR, a 621 bp coding sequence, and a 1605 bp 3 '-UTR which was virtually identical to that of the 192334 cDNA The translated 7/77 coding sequence was predicted to be 56% and 51 %ι identical/67%) and 60% similar to those of hD52 and hD53, respectively Four gaps or insertions comprising 4 or more amino acids were however required for an optimal global alignment between these sequences (Figure 8) We decided to term the novel human gene corresponding to the 7 77 cDNA, hD54. which is predicted to encode a protein of 206 amino acids with a molecular mass of approximately 22.2 kDa Analysis of the hD54 sequence with the program Pepcoil (Lupas, A , et al, Science 252 1162- 1 164 ( 1991 )) revealed the likely presence of a single coiled-coil domain from residues 37-81 (Figure 8), which shows strong similarity in both its sequence, length and position to the predicted coiled-coil domains of hD52 and hD53 (Byrne, J A , et al. Genomics 35 523-532 (1996)) Somewhat unexpectedly, it was noted that the amino acid sequences predicted by the 7/77 and 192334 sequences were not identical While residues 19-67 of 192334 were predicted to be identical to residues 158-206 of Hl l, residues 1-18 of 192334 could not be aligned with any HI 1 region (Figure 8) However, residues 1-18 of 192334 were 83% identical to residues 178-197 pfthe quail D52 orthologue RIO (Proux, V., et al, J. Biol. Chem. 277:30790-30797 (1996) and Figure 8). In addition, residues 8-20 of 192234 were identical to residues 130-142 of hD53 (Figure 8). Residues 175-197 of R10 and 130-142 of hD53 are present as insertions with respect to the global sequence alignment (Figure 8), and as such, are not present in hD52 or HI 1 sequences. In order to further investigate the possibility of hD54 coding sequence heterogeneity, the coding sequences of 4 other breast carcinoma-derived hD54 cDNAs were determined on one strand. In all cases, sequences homologous to those encoding hD53, RI 0 or 192334 sequence insertions were not present, as in the 7/77 cDNA sequence (Figure 8). However, the breast carcinoma-derived hD54 sequences were found to differ in the region predicted to encode amino acids 106-125 of Hl l (Figures 8 and 9). These 20 residues are absent from D52 and hD53 sequences, and as such form another insertion (termed ins2) with respect to the global alignment (Figure 8). In total, 2/5 cDNAs (7/7/ and E/2) contained the 60 bp sequence encoding ins2 (Figure 9). This region was absent from the Gil cDNA (Figures 8 and 9) and a further variation was noted in the identical cDNAs 7)72 and DIA, in which a 71 bp deletion (Figure 9) was predicted to remove sequences encoding ins2, and an additional 4 residues. This deletion is not produced in-frame (Figure 9), and a truncated product is predicted after 42 amino acids (Figure 8). We refer to the 3 isomeric forms of hD54 thus predicted as hD54+ins2 (from the 7/77 and E/2 cDNAs), hD54-ins2 (from the Gil cDNA), and hD54T (from the 7)72 and DIA cDNAs). Alignment of D52-like sequences also identified a 10 amino acid insert in all hD54 sequences, but not in any D52 or D53 sequences, which we termed insl (Figure 8, encoded by nucleotides 137- 166). Visual inspection of sequence alignments identified a 14 residue motif (V.M)(T,Q)X(T,S)XAYKKTXΕTL (SEQ ID NO:44) found in all D52-like sequences except hD54T (Figure 10), which will be termed hereafter the D52 motif. ThehD52, mD52, CSPP28, R10, hD53, mD53 (Byrne, J.A., etal, Cancer Res. 55:2896-2903 (1995); Byrne, J.A., et al, Genomics 55:523-532 (1996); Parente (Jr), J A., et al, J. Biol. Chem. 277:20096-20101 (1996); Proux, V., et al, J. Biol. Chem. 277:30790-30797 (1996)), and hD54-ins2 sequences bear a single D52 motif which crosses the ins2 insertion point in the global sequence alignment (Figure 8). Thus the presence of ins2 in hD54+ins2 divides the D52 motif as this occurs in hD54-ins2 (Figure 8). However, rather than removing the D52 motif, the presence of ins2 appears to create 2 closely-spaced D52 motifs in hD54+ins2, since the first 8 and last 6 amino acids of ins2 are in accordance with the last 8 and first 6 residues of the D52 motif consensus, respectively (Figures 8 and 10). Chromosomal localization of the hD54 gene In order to determine the chromosomal location of the hD54 gene, we performed in situ mapping on human metaphase spreads using the 192334 cDNA as a probe. In the 100 metaphase spreads examined after in situ hybridization, there were 191 silver grains associated with chromosomes and 53 of these (27.7%o) were located on chromosome 20. The distribution of grains on this chromosome was not random, with 45/53 (84.9%>) mapping to the ql3.2-ql3.3 region of the chromosome 20 long arm. These results allowed us to map the hD54 locus to the 20ql3.2-13.3 region of the human genome (Figure 11), a localization which is independent of these previously demonstrated for the hD52 and hD53 genes on chromosomes 8q21 and 6q22-q23, respectively (Byrne, J. A., et al, Cancer Res. 55:2896-2903 (1995)). Analysis of transcribed D 52-like sequence heterogeneity As coding sequence heterogeneity had been indicated within hD54 transcripts, Northern blot analyses were performed to assess D54 transcript lengths and levels in a panel of adult rat tissues (brain, kidney, liver, testis, stomach and skeletal muscle). A 2.3 kb D54 transcript was detected very weakly in brain and kidney after 7 days of autoradiographic exposure, whereas D54 transcripts were undetectable in liver, testis, stomach and skeletal muscle. The finding of a single D54 transcript was however in accordance with the hD54 cDNA sequence variations observed (Figures 8 and 9), which would be predicted to alter the hD54 transcript length by at most 71 bp. In order to more reliably examine potential variations in transcribed D54 sequences, PCR primers were designed to permit RT-PCR amplification of 7)54 coding sequences (Table 4). The sequences targeted by RT-PCR were those encompassing 4 insertions identified in the global alignment of D52-like sequences, since cDNA cloning had indicated that sequence heterogeneity involved D54 sequences encoding 2 such insertions, namely ins2 and ins3 (Figure 8). Furthermore, since the levels of conservation between 7 ) 52, D53 and D54 coding sequences might be predicted to reflect similarities in their respective gene structures, PCR primers were also designed for the amplification of the homologous coding regions of 7)52 and D53 genes (Table 4). Potential variations in transcribed D52-like sequences were thus investigated in 6 adult rat tissues (brain, kidney, liver, testis, stomach and cardiac atrium), in brain and liver from 12.5 dpc rat fetuses, and in brain, skeletal muscle and liver samples from 5 additional developmental time-points (14.5 dpc and 16.5 dpc, birth, and 3 and 6 weeks of age). Coding sequence heterogeneity in D54 transcripts in rat tissues RT-PCR amplification of D54 coding sequences, as predicted from the results of cDNA cloning, indicated coding sequence heterogeneity within D54 transcripts. Whereas amplification of rat D54 sequences flanking those encoding insl resulted in a single 196 bp PCR product, which sequencing confirmed to contain sequences encoding insl, in all tissue samples examined (Figure 12 A), amplification of rat 7)54 sequences flanking those encoding ins2 resulted in PCR products of 288 bp and/or 228 bp, which sequencing confirmed to contain sequences predicting the presence or absence of ins2, respectively (Figure 12B). Both 228 and 288 bp PCR products were obtained from cardiac atrium, testis, skeletal muscle and brain, whereas only the 288 bp PCR product was obtained from liver, stomach and kidney (Figure 12B). Amplification of rat D54 sequences flanking those encoding ins3 and ins4 routinely resulted in PCR products of 94 and 139 bp in all tissues examined, except brain (Figure 12C). Sequencing of the 94 bp PCR product confirmed the absence of sequences encoding ins3 and ins4 (Figure 12C). Two PCR products of 139 and 163 bp were obtained in all brain samples, with the larger 163 bp PCR product encoding an ins3 sequence of 23 amino acids (Figure 12C). The first 20 amino acids predicted by the partial-length 192334 cDNA were 90%) identical to the C-terminal 20 amino acids of this ins3 sequence (Figure 12C). Coding sequence heterogeneity in D52 and D53 transcripts in rat tissues RT-PCR amplification of 7 ) 52 and D53 sequences also indicated coding sequence heterogeneity within D52 and D53 transcripts. Whereas amplification of rat D52 sequences flanking those encoding insl or ins2 gave rise to single PCR products lacking sequences encoding insl or ins2 in all tissues examined (Figures 13 A and B), amplification of sequences flanking those encoding ins3 and ins4 resulted in up to 3 PCR products (Figure 13C). Sequencing of a 105 bp PCR product identified in all tissue samples confirmed the absence of sequences encoding ins3 or ins4 (Figure 13C). However, sequencing of a 147 bp PCR product identified in all brain samples indicated this to encode a 14 amino acid ins3 sequence (Figure 13C), which was 93%> identical to the 14 C-terminal residues of the quail D52 orthologue RIO ins3 sequence (Proux, V., et al, J. Biol. Chem. 277:30790-30797 (1996)). An additional 174 bp PCR product was detected in all brain samples other than 12.5 dpc fetal brain, and was the major PCR product identified within post-natal brain samples (Figure 13C). Sequencing of this 174 bp product identified a 23 amino acid ins3 sequence, which was 96% identical to the 23 amino acid RIO ins3 sequence, and whose 14 C-terminal residues were identical to the ins3 sequence of the 147 bp PCR product (Figure 13C). Amplification of rat 7)55 sequences flanking those encoding insl or ins2 also produced single PCR products lacking sequences encoding insl or ins2 (Figures 14AandB). However, amplification of rat D53 sequences flanking those encoding ins3 and ins4 from adult cardiac atrium, stomach, liver, kidney, testis and brain resulted in a major 160 bp PCR product (Figure 14A) whose size was not predicted from any combination of the presence or absence of sequences encoding ins3 and/or ins4 (Table 4). Sequencing of this 160 bp PCR product revealed a 100 bp internal deletion including sequences encoding ins3 and ins4 (Figure 14B). This deletion was not produced in-frame, and thus a truncated protein is predicted 3 amino acids after the deletion point (Figure 14B). In addition, sequencing of a 272 bp PCR product from 6 week and adult brain samples showed that this encodes an 18 amino acid ins3 sequence, in addition to ins4 (Figure 14B). The 13 most C-terminal residues of this ins3 sequence were identical to the mD53 ins3 sequence (Figure 14B), and the ins4 sequence was also identical to that of mD53 (Figure 14B). D52-like coding sequence heterogeneity indicated by EST database analyses The EST divisions of nucleotide sequence databases provide a resource by which sequences of randomly-selected D52, D53 and/)54 cDNAs from a diversity of cDNA libraries could be compared. We regularly performed TBLASTN searches to identify ESTs presenting significant homology with the coding sequences of D52-like cDNAs. Fifty-nine mouse, rat and human ESTs were identified of which 1 1, 14 and 34 corresponded to D52, D53 and D54 cDNAs, respectively (Table 5). The 11 D52 EST sequences (Table 5) were essentially in accordance with D52 cDNA sequences previously reported (Byrne. J A , et al, Cancer Res. 55 2896-2903 (1995), Chen, S-L , et al, Oncogene 12 741-751 (1996), Byrne, J A , etal, Genomιcs 35 523-532 (1996), Parente (Jr), J A , etal, J. Biol Chem. 271 20096-20101 (1996), Proux, V , et al, J. Biol Chem. 271 30790-30797 (1996)), as sequences encoding insl, ins2, ins3 and ιns4 were absent in 5/5, 6/6, 3 /4 and 3/3 ESTs, respectively (Table 5) A single EST from an adult human retina cDNA library (GenBank Accession No W25876) contained an additional 70 bp and 166 bp at the ins2 and ins3 insertion points, respectively, when compared with the hD52 sequence (Figure 15) The 70 bp W25876 insertion occurred at a point at which sequences encoding ins2 might be inserted (Figure 8), but shows no homology with hD54 sequences encoding ins2, and a continuation of the reading frame predicts a stop codon at nucleotides 130-132 (Figure 15) Alignment of the W25876 sequence with that of the quail D52 orthologue R10 (Proux, V , et al, J. Biol. Chem. 271 30790-30797 (1996)), indicated that the 166 bp W25876 sequence insertion encodes a 24 residue ins3 sequence which is 91 > identical to the RI 0 ins3 sequence (Figure 15) The alignment between the 2 sequences was however interrupted twice by additional sequences present in W25876 (Figure 15) The 14 D53 EST sequences (Table 5) were also largely in accordance with D53 cDNA sequences previously reported (Byrne, J A., etal, Genomics 35.523- 532 (1996)) Sequences homologous to those encoding insl and ins2 were absent from 5/5 and 3/3 ESTs, respectively, and 2 ESTs (T89899 and T93647) contained sequences encoding both ins3 and ins4 (Table 5) as predicted from both hD53 and mD53 sequences (Byrne, J A , et al., Genomics 35 523-532 (1996)) However, 5 ESTs showed evidence of a 100 bp deletion (corresponding to hD53 nucleotides 567-666), which had been previously identified in the sequence of the 83289 cDNA (corresponding to one of these 5 ESTs, GenBank Accession Nos T68402 and U44429) This deletion is predicted to introduce a frame-shift after hD53 Met 128 , resulting in a truncation after 3 amino acids (Figure 14B) A single EST (GenBank Accession No W69680) contained a similar deletion of 61 bp (corresponding to hD53 nucleotides 606-666) which is predicted to introduce an identical frame-shift after hD53 Met 141 (Figure 8) Sequences of the 34 D54 ESTs identified (Table 5) were also largely in accordance with those of the hD54 cDNAs isolated from the human breast carcinoma cDNA library A total of 22/22 ESTs included sequences encoding insl, as identified in 5/5 breast carcinoma-derived hD54 cDNAs The sequence region encoding ins2 was present in 1/9 D54 ESTs, and similarly in 1/5 breast carcinoma-derived hD54 cDNAs Ins3 was predicted to be encoded by 3/6 ESTs identified, including that corresponding to the 192334 cDNA (Figure 8) The remaining 2 ESTs predicted 14 residue ins3 sequences identical to the 14 most C- terminal residues of the 23 residue D54 ins3 sequence predicted by RT-PCR analyses (Figure 12C) Ins4 was predicted to be absent from 9/9 7)54 ESTs, as was the case for all hD54 cDNAs sequenced (Figure 8 and Table 5) Discussion We report the identification and cloning of a third member of the D52 gene family, which we have named D54 Using a strategy similar to that used to identify the second member of the 7)52 family, D53 (Byrne, J. A , et al, Genomics 55 523-532 (1996)), an EST was identified whose translated sequence showed homology to other D52-like sequences, and the corresponding 192334 cDNA was used to isolate full-length hD54 cDNAs from a human breast carcinoma cDNA library Interestingly, the 192334 cDNA was subsequently shown to contain sequences (nucleotides 1-55 of SEQ ID NO 7) that were not present in 5 breast carcinoma-derived hD54 cDNAs It might be hypothesized that these coding sequence differences could indicate that the 192334 and breast carcinoma-derived hD54 cDNAs derive from separate genes However, this is unlikely, since sequence analysis of the 192334 and 7/77 3 '-UTRs showed these to be virtually identical over 1588 bp. The assignment of a separate locus for hD54 on chromosome 20ql3.2-ql3.3, which is clearly independent of those previously demonstrated for hD52 and hD53 (Byrne, J.A., etal, Cancer Res. 55:2896-2903 (1995); Byrne, J.A., et al, Genomics 55:523-532 (1996)), confirmed that 7)54 represents a unique member of the D52 gene family. We have thus showed, as have others (Allikmets, R. , et al. , Hum. Mol. Genet 5: 1649- 1655 (1996)), that use of EST sequences is an effective strategy for characterizing members of a gene family. A comparison of the coding sequences of hD54 cDNAs indicated heterogeneity with respect to sequences encoding 2 insertions in the global alignment of D52-like protein sequences. Due to the level of identity between D52-like protein sequences we examined using RT-PCR whether sequences encoding 4 such insertions exhibited heterogeneity in transcripts from all 3 D52-like genes. As a complement to this approach, we also conducted searches of the EST divisions of nucleotide databases, in order to identify ESTs deriving from known d52-like genes. The large number of ESTs deposited in public databases means that a certain level of redundancy exists (Gerhold, D. & Caskey, C.T., Bioessays 75:973-981 (1996)), despite the use in some instances, of normalized cDNA libraries (Bonaldo, M.F., et al, Genome Res. (5:791-806 (1996)). This fact has recently been exploited to obtain information about alternative splicing events occurring in gene transcripts deriving from a variety of tissue types (Wolfsberg, T.G. & Landsman, D., Nucleic Acids Res. 25:1626-1632 (1997)). In the present study, data from cDNA cloning, RT-PCR and EST sequence analyses have suggested that while certain insertions in the global alignment of D52-like sequences reflect constitutive differences between individual D52-like genes, others are likely to result from alternative exon splicing. Sequences encoding insl and ins4, as identified in hD54 and D53 cDNA sequences (Byrne, J.A., et al, Genomics 55:523-532 (1996)), respectively, were uniquely and consistently identified in 7)54 or D53 transcripts only. When PCR primers encompassed sequences flanking the insl insertion point, single PCR products were obtained from all 3 D52-like genes in all rat tissue samples examined In the case OΪD54 transcripts, PCR products encoded insl, but in the case of D53 and D52 transcripts sequences encoding insl were absent Similarly, all 22 D54 ESTs which included sequences flanking the insl insertion point encoded an insl sequence, whereas none of the D52 or D53 ESTs included homologous sequences Thus insl is predicted to be encoded by a D54 coding region which represents a constitutive difference between D54, D52 and D53 genes Similarly, RT-PCR and EST sequence analyses identified sequences encoding ins4 as a constitutive coding sequence difference between D53 transcripts, and 7)52 and D54 transcripts In contrast, ins2 and ins3 sequences appear to be encoded by alternatively- spliced exon(s) present in one or more D52-like genes The results of cDNA cloning, RT-PCR, and EST sequence analyses indicated that sequences encoding ins2 were either present in or absent from D54 transcripts However, these approaches did not identify homologous sequences encoding similar amino acid sequences in either 7 ) 52 or D53 transcripts One hD52 EST W25876 contained a 70 bp sequence insertion with respect to D52 cDNA sequences at the point at which sequences encoding ins2 might be inserted, but this sequence showed no homology with hD54 sequences encoding ins2 That a continuation of the W25876 reading frame predicts a stop codon suggests that this EST derives from an incompletely spliced transcript and that the 70 bp insertion represents intronic sequence The point at which sequences encoding ins2 would be predicted to be inserted in the R/0 gene has also been indicated to represent an exon-intron boundary (Proux, V., et al, J. Biol Chem. 277.30790-30797 (1996)), indicating structural similarities between quail and human D52 genes Thus, ins2 appears to be encoded by one or more alternatively-spliced D54 exons for which equivalents may not exist in D52 or D53 The presence of ins2 in D54 isoforms would not appear to pertain to any putative spatio- or temporally-specific D54 protein function, as the alternative splicing of sequences encoding ins2 did not seem to be regulated in an obviously tissue-specific or temporal fashion Sequence analyses predict that the significance of ins2 lies in the fact that its presence effectively duplicates hD54-ins2 residues Val 100 -Ala 105 and Tyr 106 - Leu 113 , found N- and C-termmal to the ms2 insertion point, respectively The residues Val 100 -Ala 105 are homologous to D52 residues Val 90 -Ala 95 which map withing a larger regions (Gly 72 -Ala 95 ), implicated as being involved in mediating protein-protein interactions of D52/N8 (Chen et al, Oncogene 75 2577-2588 (1997), Byrne etal , Oncogene 16 873-882 (1998)) In these studies, a truncated hD52/N8 protein N8LZ (Met'-Ala 95 ) did not form homomeric interactions, unlike wild-type D52/N8, whereas a truncated mD52 bait protein (Met'-Ala 95 ) formed interactions withing the yeast two-hybrid system Therefore, whereas interactions mediated by D52 proteins had been previously attributed to the coiled-coil domain, residues Gly 72 -Ala 95 may therefore also be necessary, or even sufficient, for certain interactions to occur Since the corresponding D54 region (Gly 82 - Ala 105 ) is well conserved, this implicated ins2, as potentially modulating interactions mediated by D54 The interactions mediated by the hD54 isoforms hD54+ins2 and hD54-ins2 and other D52-like proteins were recently examined, and while it was found that the presence of ins2 did not obviously alter interaction preferences, both hD54 isoforms interacted more strongly with hD54+ins2 than with hD54-ins2 (Byrne et al, Oncogene 16 873-882 (1998)) Whereas alternatively- spliced coding sequences encoding ins2 were only identified in 7)54 transcripts, sequences encoding ins3 appeared to be subject to alternative splicing in all 3 D52-like genes Sequences encoding a 13 residue ins3 sequence were initially identified in hD53 cDNAs from breast carcinoma and fetal liver-spleen, but not in D52 cDNAs from several tissues (Byrne, J A , et al, Cancer Res. 55 2896-2903 (1995), Chen, S-L , et al, Oncogene 72 741-751 (1996), Byrne, J A , et al, Genomics 35 523-532 (1996), Parente, J A et al, J. Biol Chem. 277 30790-30797 ( 1996)) However, the present study has indicated that sequences encoding ιns3 can be present in D52 and D54 transcripts, particularly those expressed in neural tissues The presence of sequences encoding ιns3 in D54 transcripts was first indicated by the partial-length 192334 cDNA from adult human brain. The 20 predicted N-terminal 192334 residues were 90% identical to the C-terminal 20 residues of a 23 residue ins3 sequence predicted by the quail/)52 orthologueR/0 (Proux, V., etal, J. Biol. Chem. 277:30790-30797 (1996)), the R10 cDNA having been isolated from an embryonic neuroretina cDNA library. RT-PCR analyses subsequently predicted a 23 residue ins3 sequence in D54 transcripts from post-natal brain samples, which was 75% identical to the R10 ins3 sequence. A shorter 14 residue ins3 sequence predicted by 2 mouse D54 ESTs (Table 5) was identical to the C-terminal 14 amino acids of the longer D54 ins3 sequence. Similarly, RT-PCR analyses of D52 transcripts from post-natal rat brain samples indicated that the major PCR product encoded a 23 residue ins3 sequence which was 96% identical to the R10 ins3 sequence. A shorter PCR product obtained from both fetal and post-natal brain samples predicted a 14 residue ins3 sequence identical to the 14 C-terminal residues of the longer ins3 sequence. As a larger 18 residue ins3 sequence was also identified in rat D53 transcripts from 6 week and adult brain samples, the 13 most C-terminal residues of which were identical to the 13 residue D53 ins3 sequences previously reported (Byrne, J.A., et al, Genomics 55:523-532 (1996)), it appears that transcripts from all 3 D52 genes may encode long and short forms of ins3. RT-PCR analysis of 7)54 and D52 transcripts indicated those encoding long ins3 sequences were only identified in brain samples, thus providing an example where alternative splicing of D52 and D54 sequences appears to be regulated in a tissue-specific fashion. In addition, since PCR products predicting 23 residue D52 or D54 ins3 sequences were also more abundant in post-natal brain samples, the alternative splicing of these sequences appears to be temporally regulated. This additionally suggests that the presence of D52 and D54 transcript sequences encoding long ins3 sequences correlates with brain maturation processes. The W25876 EST, deriving from an apparently incompletely-spliced D52 transcript from human retina, provides a possible explanation for the existence of short and long ins3 sequences in D52-like proteins. An alignment of the W25876 nucleotide sequence with those of hD52 and RIO indicates that the W25876 sequence encodes a 23 amino acid ins3 sequence which is 91% identical to that of RIO. The position of non-aligned W25876 sequence with respect to the RIO sequence, combined with the absence of ins3 sequences in some D52 transcripts (Byrne, J.A., et al, Cancer Res. 55:2896-2903 (1995); Chen, S-L., et al, Oncogene 12:74\-75\ (1996); Byrne, J A., et al, Genomics 55:523-532 (1996); Parente, J.A. etα/., J Biol Chem. 277:30790-30797 (1996)) suggests that the 23 residue hD52 ins3 sequence is contributed to by at least 3 separate exons, including a very small 4 bp exon. The use of multiple exons may thus determine the ultimate length of encoded ins3 sequences as reported for tissue-specific forms of the neural cell adhesion molecule (N-CAM), where 4 exons (including one of 3 bp) were found to encode a 93 bp insert in N-CAM mRNAs specific for chicken heart and skeletal muscle (Prediger, E.A., et al., Proc. Natl. Acad. Sci. USA 55:9616-9620 (1988)). While sequences encoding ins3 regions were observed to be either present in or absent from D52 and 7)54 transcripts, the absence of such sequences from D53 transcripts was only produced by a 100 bp deletion predicted to introduce a frame-shift after Met 128 , and resulting in a truncated D53 product. This 100 bp deletion does not appear to occur in a tissue-specific fashion, having been identified in 7)55 transcripts from 10 rat, mouse and human tissues using RT-PCR, EST sequence analyses, and a yeast two-hybrid screening approach. The fact that similarly-truncated proteins were not predicted by 7)52 or 7)54 sequences suggests functional differences between D53, and other D52-like proteins. However, the diversity of alternative splicing events affecting sequences encoding ins3 in all 3 genes strongly indicates that the presence or absence of ins3 sequences plays an important role in modulating D52-like protein function. In summary, we have isolated and characterized a third member of the breast carcinoma-derived D52 gene family, and using a combination of approaches, have indicated that a wealth of protein isoforms may be produced from all 3 D52-like genes. In particular, alternative splicing events involving sequences encoding ins3 sequences appear to be regulated in a tissue-specific and temporal fashion in the case of 7)52 and D54 genes Materials and Methods cDNA Library Screening The cDNA 192334, originally isolated by the IMAGE consortium (Lennon, G , et al, Genomics 33 151-152 (1996)) was purchased from Genome Systems, Inc (St Louis, MO) A random-primed 32 P -labeled _5αmHI-EcoRI clone 192334 fragment (including nucleotides 1-188 of SEQ ID NO 7) was used to screen 600,000 plaque forming units from a breast carcinoma cDNA library, basically as described (Byrne, J.A , et al, Cancer Res. 55 2896-2903 (1995)). Chromosomal localization Chromosomal localization of the hD54 gene was performed using chromosome preparations obtained from phytohemagglutinin-stimulated lymphocytes as previously described (Byrne, J A , et al, Cancer Res. 55 2896- 2903 (1995)) The 192334 cDNA was 3 H-labeled using nick-translation to a final specific activity of 1 X 10 8 dpm/μg, and hybridized to metaphase spreads at a final concentration of 100 ng/ml of hybridization solution, as described (Mattei, M.G., et al , Hum. Genet. 69 268-271 (1985)) Autoradiography was performed using NTB2 emulsion (Kodak) for 18 days at 4°C RNA extraction and northern blot analyses Brain, skeletal muscle and liver samples were dissected from 14 5 dpc and 16 5 dpc rat fetuses, and from neonatal, 3 week old and 6 week old female Sprague-Dawley rats. Only brain and liver samples were dissected from 12 5 dpc fetuses. Where tissues were dissected from multiple animals, these were pooled prior to RNA extraction. Total RNA was extracted from frozen tissue samples using TRIzol reagent, according to instructions supplied by the manufacturer (Gibco BRL, Life Technologies, Inc, Australia). Total cellular RNA was isolated from 7 tissue samples (skeletal muscle, cardiac atrium, stomach, testis, liver, kidney and brain) obtained from adult rats using the guanidine hydrochloride procedure (Strohmann, R.C., etal, Cell 70:265-273 (1977)). Ten μg aliquots of total RNA were subjected to Northern blot analysis basically as described (Byrne, J.A., et al, Cancer Res. 55:2896-2903 (1995)). Filters were hybridized successively with 32 P-labeled cDNA fragments deriving from 192334 (including nucleotides 1-188 of SEQ ID NO:7), and 36B4 (Masiakowski, P., etal, Nucleic Acids Res. 70:7895-7903 (1982)) cDNAs, the latter representing a ubiquitously expressed gene. Filters were washed to final stringencies of 1 X SSC, 0.1% SDS at 65 °C or 0.1 X SSC, 0.1% SDS at 65 °C following hybridizations employing the 192334 or 36B4 probes, respectively. cDNA synthesis and RT-PCR amplification Ten μg samples of total RNA primed with random hexamers were reverse- transcribed using Superscript II Reverse Transcriptase in total reaction volumes of 50 μl, according to the manufacturers instructions (Gibco BRL, Life Technologies, Inc.). Control reactions were routinely included where the RNA template was omitted. One half μl of each cDNA synthesis reaction was subjected to RT-PCR amplification in 40 μl reaction volumes including 4 μl 10 X PCR buffer containing magnesium (Boehringer Mannheim), 0.8 μl PCR nucleotide mix (10 mM each dNTP) (Boehringer Mannheim), 0.4 μl each primer (100 mM), and 0.2 μl Taq DNA polymerase (5 U/μl) (Boehringer Mannheim). Reactions were first denatured at 94 °C for 3 min, followed by 30 cycles of denaturation (94 °C for 45 s), annealing (55 or 60 °C for 1 min 30 s or 1 min), and elongation (72 °C for 1 min) in a DNA Engine PTC-200 (MJ Research). The final elongation step was performed at 72 °C for 5 min PCR products were separated on 4-5% MetaPhor agarose gels (FMC BioProducts Corp ) run overnight at 30-40 V PCR primers for RT-PCR analyses were based upon the human and/or mouse D52-like sequences (GenBank Accession Nos U44426, AF004428, AF004430 and W82290) Three sets of primers were synthesized for each D52-like gene (see below) As a positive reaction control, and also to assist in sizing PCR products, PCR amplifications were also performed using an appropriate mouse or human 7)52, D53 or D54 cDNA template Negative RT-PCR amplification controls consisted of those in which the cDNA template had been omitted and/or replaced by a control cDNA synthesis reaction in which the RNA template had been omitted Purification of PCR products for sequencing PCR products of interest were excised from agarose gels, and following centrifugation through siliconized glass wool, 2 μl elutant was re-amplified using the previous PCR amplification conditions (see above) The sizes and purity of PCR products were reconfirmed using agarose gel electrophoresis PCR products were then purified on PCR SPINCLEAN columns according to the manufacturer' s instructions (Progen Industries Ltd, Australia) DNA sequencing Mini-preparations of plasmid DNA were purified by NaCI and polyethylene glycol 6000 precipitation, and sequenced with Taq polymerase and T3 and T7 universal primers, or internal primers, and dye-labeled ddNTPs for detection on an Applied Biosystems 373A automated sequencer Sequencing of PCR products was performed using internal primers and/or PCR primers, where suitable internal primers could not be designed Sequence analyses Searches of nucleotide databases were performed using the TBLASTN program (Altschul, S.F., et al, J. Mo . Biol. 275:403-410 (1990)), using D52, D53 and hD54+ins2 amino acid sequences as the query sequence. Multiple nucleotide or amino acid sequences were aligned using CLUSTAL (Thompson, J.D., et al, Nucleic Acids Res. 22:4673-4680 (1994)), with other analyses employing programs from the GCG package, including Pepcoil, for the identification of coiled-coil domains (Lupas, A., et al, Science 252: 1162-1164 (1991)). Example 4: Increased copy number ofhD54 in breast carcinomas Increased dosage of cellular oncogenes is a frequent genetic abnormality displayed by tumor cells (Schwab M. and Amler L.C., Genes Chromosome Cancer 7: 181-193 (1990); Schwab M. BioEssays, 20:473-479 (1998)), and the study of oncogene amplification has been of seminal importance in molecular oncology. The genome scanning technique of comparative genomic hybridization (CGH) has indicated that several regions apart from those classically studied can be gained in breast carcinoma, one such region being the long (q) arm of chromosome 8 (reviewed by Forozan et al, Trends Genet. 75:405-409 (1997); Knuutila et al.,. J. Am. Pathol, 752: 1107-1 123 (1998)). Chromosome 8q has been observed to be amongst the most frequently gained regions (Kallioniemi et al, Proc. Natl Acad. Sci. USA 97:2156-2160 (1994): Isola et α/., Am. J. Pathol, 747:905-911 (1995); Reid et al, . Cancer Res. 55:5415-5423 (1995); Nishizaki et al, J. Int. Cancer (Pred. Oncol). 74:513-517 (1997a); Nishizaki et al, Genes Chromosom. Cancer 79:267-272 (1997b); Tirkkonen et al, Genes Chromosom. Cancer 27: 177-184 (1998)), or indeed the most frequently gained genomic region, in breast cancer (Muleris et al, Genes Chromosom. Cancer 10: 160-170 (1994); Courjal et al, Cancer Res. 57:4360-4367 (1997)). Nishizaki et al, Genes Chromosom. Cancer 79:267-272 (1997b) reported that the gain of chromosome 8q was significantly more frequent in ductal than in lobular cancers, and similarly, Afify A. et al, Breast Cancer Res. Treat., 55:201-208 (1996), detected chromosome 8 gain in infiltrating ductal carcinomas and ductal carcinoma in situ but not in lobular or pillary card benign lesions. In a genome-wide screen to detect genetic changes associated with clinical outcome in node-negative breast cancer, Isola etα/., Am. J. Pathol., 747:905-91 1 (1995) reported that a high-level gain of chromosome 8q was significantly associated with recurrence. These combined data suggest that chromosome 8q gain is a frequent event defining a subset of breast carcinomas, which is of potential prognostic significance. That-gain of the 8q chromosomal arm reflects the existence of more than one 8q target gene was suggested by the finding that the 8q24, 8q22-q23 and 8q21 regions could be gained separately in breast cancers or cell lines (Kallioniemi et al, Proc. Natl. Acad. Sci. USA 97:2156-2160 (1994)). Regions including chromosome bands 8q24, 8q23 and/or 8q22 have been observed to be separately gained in other breast cancer studies (Muleris et al, Genes Chromosom. Cancer 70: 160-170 (1994); Reid et al.,. Cancer Res. 55:5415-5423 (1995), Courjal et al.,. Cancer Res. 57:4368-4377 (1997); Nishizaki et al, J. Int. Cancer (Pred. Oncol). 74:513-517 ( 1997a); Nishizaki etal. , Genes Chromosom. Cancer 79:267- 272 (1997b)), and in other cancers such as bladder cancer (Kallioniemi A., et al, Genes Chromosom. Cancer 72:213-219 (1995); Richter et al, Cancer Res. 57:2860-2864 (1997)), hepatocellular carcinoma (Fujiwara et al, Cancer Res. 55:857-860 (1993)), lung cancer (Balsara et al., Cancer Res. 57:21 16-2120 (1997), Petersen et al, Cancer Res. 57:2331-2335 (1997)), osteosarcoma (Tarkkanenetα/., Cancer Res. 55: 1334-1338 (1995)), ovarian cancer (Sonodaet al, Genes Chromosom. Cancer 20:320-328), and prostate cancer (Cher et al, Genes Chromosom. Cancer 77: 153-162 (1994), Visakorpi et al, Cancer Res. 55:342-347 (1995); Van Den Berg et al, Clin. Cancer Res. 7: 1 1 -1 8 (1995)). The c-myc gene may represent a target gene where gains include chromosome 8q24 (Jenkins et al, Cancer Res. 57 524-531 (1997)), although data exist to suggest that q-Myc represents a surrogate marker in some cases (Sauter et al, Am. J. Pathol 146 1131-1 139 (1995), Visscher et al. , Genes Chromosom Cancer 18 1 -7 (1997)) The E2F5 gene at chromosome 8q22 was found to be present at ICN, albeit at low levels, in 4 2% of breast cancers (Courjal et al, Cancer Res. 57 4360-4367 (1997), Courjal et al , Cancer Res. 57 4368-4377 (1997)), but its status as a target gene was not investigated The chromosome 8q21 band was separately gained in the SK-BR-3 breast cancer cell line (Kallioniemi et al, Proc. Natl. Acad. Sci. USA 91 2156-2160 ( 1994)), and also either represented, or was included within, a minimal commonly- gained chromosome 8q region in prostate cancer (Cher et al, Genes Chromosom. Cancer 11 153-162 (1994), Cher et al, Cancer Res. 56 3091-3102 (1996)), bladder cancer (Kallioniemi A , et al, Genes Chromosom. Cancer 12 213-219 (1995), Richter et al, Cancer Res. 572860-2864 (1997)) and osteosarcoma (Tarkkanen etal, Cancer Res. 55 1334-1338 (1995)) This suggests that one or more target genes are located at 8q21 , which could have a role in the initiation or progression of multiple cancers However, a comparative lack of candidate molecular probes to this region has meant that no candidate 8q21 target gene has been proposed in breast or any other cancer Determination ofD52-like Gene Copy Number in Breast Carcinomas Using Southern Analyses As both hD52 and hD54 genes map to genomic regions which are frequently present at ICN in human breast carcinoma (chromosomes 8q21 and 20ql 3 2-ql 3 3, respectively), RCN at the hD52 and hD54 loci was determined in a panel of human breast carcinomas using Southern blot analyses Southern blot analyses were performed using EcoRI restricted genomic DNA samples, and a doublet of 2 1 kb and 2 2 kb were the major restriction fragments detected by a hD52 cDNA probe A h_D54 cDNA probe detected a doublet of approximately 20 kb and 23 kb on the same filters, whereas a hD53 cDNA probe detected a single 2 4 kb EcoR I fragment The signal intensities of these bands were measured densitometπcally, and used to calculate RCN at hD52 and hD54 loci, using the hD53 locus as a control locus The hD53 gene maps to chromosome 6q22-q23, which is not (Reid et al , Cancer Res 55 5415-5423 (1995)) or only infrequently (Kallioniemi etal , Proc Natl Acad Sci USA 91 2156-2160 (1994), Muleris et al , Genes Chromosom Cancer 10 160-170 (1994)) present at ICN in human breast carcinomas, and therefore represents a suitable control Signal intensities obtained with the hD53 probe were also compared with those obtained at a second control locus, fibronectin- 1 (FN-1), located at chromosome 2q34, which is also not (Muleris et al , Genes Chromosom Cancer 10 160- 170 ( 1994), Reidetal , CancerRes 55 5415-5423 (1995)) or infrequently (Kallioniemi etα/ , Proc Natl Acad Sci USA 97 2156-2160 (1994), Nishizaki et al , Genes Chromosom Cancer 19 267-272 ( 1997b)) present at ICN in human breast cancer, and with the intensity of ethidium bromide staining within restricted DNA samples following electrophoresis, in order to verify that hD53 represented a suitable control locus Three tumors (9% of cases) showed ICN (RCN>2 0) at the hD52 locus, and 3 different tumors showed ICN at the hD54 locus (Table 6) Of the 6 tumors showing ICN at hD52 or hD54 loci, measured increases in copy number were low (2 1- to 2 8-fold increases) in 4 cases, whereas the remaining 2 cases showed higher (4 9- or 7 8-fold) increases All tumors showing ICN at hD52 or hD54 loci were infiltrating ductal carcinomas This indicates that hD52 and hD54 loci are present at ICN in some 9% of breast carcinomas, which are in turn primarily infiltrating ductal carcinomas Immunohistochemical Analysis of hD52 Protein Expression in Paraffin- embedded Breast Carcinoma Sections Increases in hD52 RCN (2 4- and 2 8-fold) or hD54 RCN (2 3- and 4 9- fold) were measured in 4 of 10 tumors which exhibited overall moderate intensity of lιD52 staining in cancer cells (cases 28 and 25, and cases 3 and 17, respectively) (Table 6) In the 5 tumors, hD52 staining of cancer cells was weak (Table 6), presenting as diffuse cytoplasmic staining Increases in hD52 RCN were not found in these tumors, although case 4 was indicated to have a low-level (2 1 -fold) increase in hD54 RCN (Table 6) In the 3 tumors examined where hD52 was undetectable, no increases in hD52 or hD54 RCN were found (Table 6) Table 6 Relative copy number (RCN) at hD52 and hD54 loci in 32 breast carcinomas, compared with hD52 protein expression, as determined using immunohistochemistry a hD52 protein levels are shown according to the following scale: 0=not detected, +=weakly detected, ++=moderately detected, +++=strongly detected. b ND=not done. Discussion In the present study, we have investigated whether the chromosome 8q21 hQ52 (TPD52) locus represents a target gene within chromosomal gains or amplifications encompassing this region in human breast cancer. Alterations in copy number at hD52 and hD54 were investigated using Southern blot analyses in a panel of 32 breast carcinomas. The hD54 locus has been mapped to chromosome 20ql3.2-ql3.3 (Nourseetα/., Biochim. Biophys. Acta 7445: 155-168 (1998)), another region which is frequently gained in breast (Kallioniemi et al, Proc. Natl. Acad. Sci. USA 97:2156-2160 (1994); Courjal et al, Cancer Res. 57:4360-4367 (1997); Courjal et al.,. Cancer Res. 57:4368-4377 (1997); Tirkkonen et al, Genes Chromosom. Cancer 27: 177-184 (1998)) and other carcinomas (Solinas-Toldo et al, Cancer Res. 5(5:3803-3807 (1996), Sonoda et al, Genes Chromosom. Cancer 20:320-328 (1997)). Three tumors (9%> of cases) showed ICN at the hD52 locus, and 3 different tumors showed ICN at the hD54 locus. In each group of tumors showing ICN at hD52 or hD54 loci, one tumor showed copy number increases indicating regional amplification encompassing hD52 or hD54, whereas in the remaining cases, increases in copy number were low, and possibly consistent with the gain of an entire chromosome or chromosomal arm (Schwab and Amler., Genes Chromosom. Cancer 7: 181-193 ( 1990)). However, since cancer cells are typically diluted two-fold by stromal and other cell types in human breast carcinoma (Visscher et al, Genes Chromosom Cancer 75: 1-7 (1997)), the use of Southern blot analyses to measure changes in hD52 and hD54 dosage may have lead to both an underestimation of the extent to which copy number was increased, and of the number of tumors harboring ICN at hD52 or hD54 loci. That this was indeed the case is suggested by a comparison of the results obtained in the present study with those of a past study, where FISH showed YAC 936B3 (containing hD52) to be present at ICN relative to the chromosome 8 centromere in 5/8 breast cancer cell lines and 6/10 primary breast tumors analyzed (Schoenberg et al, Genes Chromosom. Cancer 22: 105-113 (1998)). Materials and Methods Human cell lines and tissues The MCF7 and BT474 breast cancer cell lines, the HL60 myelocytic leukemia cell line, and the HFL 1 foetal lung fibroblast cell line, are described in the American Type Culture Collection Catalogue (8th Edition). Paraffin-embedded tissue sections and surgical breast carcinoma specimens were obtained from Westmead Hospital, Australia. Surgical specimens were stored in liquid nitrogen prior to genomic DNA extraction, which was performed using standard techniques (Ausubel et al. , Current Protocols in Molecular Biology Vol. 1 , John Wiley & Sons, Inc. New York (1997)). Of the 32 breast carcinomas examined, the tumor type was known in 31 cases, of which 24 cases represented infiltrating ductal carcinomas. The remaining 7 cases represented carcinomas of other types (3 lobular, 2 mucinous, and 1 each of carcinoid and tubular types). Thirty and 22 tumors were positive for the presence of estrogen or progesterone receptors, respectively, with only one tumor being both estrogen- and progesterone receptor- negative. The mean patient age was 63 years. The 6 normal breast samples examined showed no signs of epithelial hyperplasia or malignancy, and the mean patient age was 39 years. Southern Blot Analyses and Quantification of Hybridization Signals Approximately 10 μg genomic DNA from each of 32 primary breast cancers, and samples of DNA from a healthy female control subject, were digested with EcoR I overnight at 37°C. Samples were electrophoresed through 1 % agarose gels, with a sample of restricted control DNA being included on each gel, and transferred to nylon membranes (HybondN+, Amersham). Southern blot hybridizations were performed successively with 32 P- 1 labelled inserts from hD52, hD53, hD54 and FN-1 (Byrne et al, 1995) cDNAs. Hybridizations and subsequent washing steps followed standard procedures, and filters were exposed to Kodak AR film for 8-23 h, to obtain exposures of varying intensity for each probe. Hybridization signals were quantitated using a computing densitometer (Molecular Dynamics). To calculate RCN, signals obtained in tumor samples were divided by that obtained in a control DNA sample loaded on the same gel from a healthy female volunteer, to correct for lane loading discrepancies. Corrected signals at test (hD52 or hD54) loci were then divided by the corrected signal obtained at the control hQ53 locus. The overall formula used to calculate RCN was therefore (tumor signal AD 2 or ^/control signal ADW or W54 ) I (tumor signal ADJJ control signal hD53 ), and a RCN>2.0 was considered to indicate ICN (Courjal et al, 1997).

Claims: What Is Claimed Is: 1. An isolated nucleic acid molecule comprising a polynucleotide having a nucleotide sequence at least 90% identical to a sequence selected from the group consisting of: (a) a polynucleotide encoding amino acids 1 to 206 of SEQ ID NO:6; (b) a polynucleotide encoding amino acids 2 to 206 of SEQ ID NO:6; (c) a polynucleotide fragment of (a) or (b), wherein said fragment is at least 15 bp in length and does not have a sequence described in GenBank Accession Nos. AA004043 (SEQ ID NO:76), AA008731 (SEQ ID NO:77), AA031903 (SEQ ID NO:78), AA103819 (SEQ ID NO:79), AA124904 (SEQ ID NO:80), W10501 (SEQ ID NO:81), W20813 (SEQ ID NO:82), W54810 (SEQ ID NO:83), W66669 (SEQ ID NO:84), W82290 (SEQ ID NO:85), W91446 (SEQIDNO:86), W97219 (SEQ IDNO:87), AA218395 (SEQ ID NO:88), AA268015 (SEQ ID NO:89), AA266320 (SEQ ID NO:90), AA255184 (SEQ ID NO:91), W75292 (SEQ ID NO:92), AA048792 (SEQ ID NO:93), H31879 (SEQ ID NO:94), AA277778 (SEQ IDNO:95), W13944 (SEQ ID NO:96), H39077 (SEQ ID NO:97), AA411964 (SEQ ID NO:98), AA124922 (SEQ ID NO:99), AA116313 (SEQ IDNO:100), W75408 (SEQ ID NO:101), or AA436748 (SEQ ID NO: 102); (d) a nucleotide sequence complementary to the nucleotide sequence of any of the polynucleotides of (a), (b), or (c). 2. The isolated nucleic acid molecule of claim 1, wherein said polynucleotide encodes amino acids 1 to 206 of SEQ ID NO:6. 3. The isolated nucleic acid molecule of claim 1, wherein said polynucleotide encodes amino acids 2 to 206 of SEQ ID NO:6. 4 The isolated nucleic acid molecule of claim 1 , which is a DNA molecule 5 The isolated nucleic acid molecule of claim 1 , which is an in vitro RNA transcript 6 The isolated nucleic acid molecule of claim 4 wherein said polynucleotide is cDNA 7 A method for making a recombinant vector comprising inserting the isolated nucleic acid molecule of claim 1 into a vector 8 A recombinant vector produced by the method of claim 7 9 A method of making a recombinant host cell comprising introducing the recombinant vector of claim 8 into a host cell 10 A recombinant host cell produced by the method of claim 9 11 A recombinant method for producing a polypeptide comprising culturing the recombinant host cell of claim 10 12 An isolated polypeptide having an amino acid sequence at least 95%o identical to a sequence selected from the group consisting of (a) amino acid residues 1 to about 206 of SEQ ID NO 6, and (b) amino acid residues 2 to 206 of SEQ ID NO 6 13 The isolated polypeptide of claim 12, wherein said polypeptide has the amino acid sequence of amino acid residues 1 to 206 of SEQ ID NO 6 14. The isolated polypeptide of claim 12, wherein said polypeptide has the amino acid sequence of amino acid residues 2 to 206 of SEQ ID NO:6. 15. A method for determining the prognosis of breast cancer, comprising: (a) assaying a first hD54 gene expression level or gene copy number in breast tissue; and (b assaying a second hD54 gene expression level or gene copy number in breast tissue; whereby relative levels of said first gene expression level or gene copy number over said second is a prognostic marker for breast cancer.

Inventors: BYRNE JENNIFER A, BYRNE, JENNIFER, A.
Applicants: BYRNE JENNIFER A, CENTRE NAT RECH SCIENT, INST NAT SANTE RECH MED, SQUIBB BRISTOL MYERS CO, UNIV PASTEUR, BRISTOL-MYERS SQUIBB COMPANY, BYRNE, JENNIFER, A., CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE, INSTITUT NATIONAL DE LA SANTE ET DE LA RECHERCHE MEDICALE, UNIVERSITE LOUIS PASTEUR, STRASBOURG
Application year: 1999
Main classification: C12N15
IPC codes: C07K14, C12N1, C12N5, C12N15, C12P21, C12Q1