A METHOD OF IDENTIFYING HORMONE RECEPTOR LIGANDS

Abstract: The present invention relates to methods of identifying compounds which are modulators of nuclear receptors, including retinoid, steroid, glucocorticoid, thyroid, vitamin D and peroxisome proliferator receptors.

Description: A METHOD OF IDENTIFYING HORMONE RECEPTOR LIGANDS FIELD OF THE INVENTION The present invention relates to compounds which are modulators of nuclear receptors, particularly, retinoid receptors, as well as methods of identifying such compounds. BACKGROUND OF THE INVENTION Retinoids, synthetic and natural derivatives of retinoic acid, are compounds which are well known in the art. It is generally recognized that retinoid-like activity is useful in the treatment of mammals, including humans, for curing or alleviating symptoms associated with numerous diseases and conditions. Retinoids are known particularly for their ability to regulate cellular processes in vivo such as cellular proliferation and differentiation, and to modulate apoptosis or programmed cell death (Yang et al., Proc. Natl. Acad. Set U.S.A. 90:6170 (1993); Delia et al., Cancer Res. 53:6036 (1993)). These activities have made retinoids especially useful in the treatment of dermatological disorders and oncology. For example, retinoic acid, a metabolite of vitamin A, has been shown to have a remedial effect on acute promyelocytic leukemia (Chomienne et al., FASEB J. 10:1025 (1996)). Retinoids have also been shown to inhibit LL-6 production, suggesting a therapeutic benefit in the treatment of LL-6 associated diseases such as psoriasis and rheumatoid arthritis (Zitnik et al., J. Immunol. 152:1419 (1994), and Kagechika, H. et al., Biochem Biophys. Res. Commun. 231:243 (1997)). At present, it is generally recognized that retinoids exert their biological effect through their interaction with nuclear receptors. Retinoid receptors, which are divided into two families, retinoic acid receptors (RARs) and retinoid X receptors (RXRs), are ligand-dependent transcription factors that regulate gene expression by two different pathways (Nagpal et al., Current Pharmaceutical Design, 2:295 (1996), and references cited therein). Retinoid receptors, similar to all members of the steroid superfamily which includes the vitamin D receptor, the glucocorticoid receptor, thyroid hormone receptors, peroxisome proliferator activated receptors and steroid receptors such as the estrogen receptor and androgen receptor, can modulate gene expression by either binding to retinoic acid response elements (RAREs) present in the target genes, or by altering the action of certain transcription factors that bind to the DNA in the regulatory sequences of the target genes. Nuclear receptors such as RAR can be divided into six functionally different domains defined as regions A through F. Regions A and B together, located at the N- terminus of the receptor, comprise a transactivation function known as AF-1. In the retinoid receptor RAR, the A/B domain modulates transcription independently of retinoid binding. Region C is a highly conserved domain that functions as the DNA binding domain (DBD) and is responsive to cognate cis-acting response elements. The presence in this region of two cysteine-rich zinc fingers, common among other DNA binding proteins, facilitates critical interactions with specific nucleotide sequences of the RAREs. Next to the DNA binding domain is region D, or the hinge domain. Region E contains a ligand binding domain (LBD), which serves a retinoid-dependent activation function, referred to as AF-2, and a dimerization function. This region contains hydrophobic leucine zipper motifs. The function of region F, located at the C-terminus, is still largely unknown. RXRs are similar to RARs in that they are modular and possess similar function, but lack region F. Other members of the steroid superfamily contain analogous elements to RAR, and can form heterodimers with RXR. Within each nuclear receptor family there are distinct receptor subtypes. For example, for each of the retinoid receptors, RAR and RXR, there are α, β and γ subtypes. For the estrogen receptor, there are the α and β subtypes; whereas for the peroxisome proliferator receptor, there are α, β and γ subtypes. Other yet to be discovered subtypes of each of these receptors may exist. Furthermore, there are additional differences in the A/B region between the RAR receptor subtypes that arise from alternative splicing and/or the use of different promoters. For the RARα subtype, there are expressed two main isoforms (αl and α2); for the RARβ subtype, there are four main isoforms (βl, β2, β3 and β4); and for the RARγ subtype there are two main isoforms (γl and γ2). Isoforms for the RXR subtypes are also believed to exist. RARs are known in the art to induce gene expression by binding to the retinoic acid responsive elements (RAREs) present in the promoter regions of retinoic acid- responsive genes as RAR-RXR heterodimers (Nagpal et al., EMBO J. 12:2349 (1993) and Mangelsdorf et al., The Retinoid Receptors in The Retinoids: Biology. Chemistry and Medicine. 2nd edition, eds. Sporn et al., Raven Press, Ltd., New York 1994, the disclosure of each of which is hereby incorporated by reference). Recently, CBP/p300, Sugl Tripl, ΗF1, SRC-1 N-CoAl and TLF2/GRLP1 have been identified as co-factors which interact with RARs and other nuclear receptors in a ligand dependent manner (Glass et al., Curr. Opin. Cell Biology 9:222 (1997)). Biochemical evidence has supported models of transcriptional activation involving the loosening of the nucleosomal core as well as the disassociation of HI histone from the nucleosome structure near the promoter regions of actively transcribing genes. Both CBP/p300, its associated protein p/CAF, and SRC-1 have intrinsic histone acetyl transferase (HAT) activity (Bannister et al., Nature 384:641 (1996), Yang et al., Nature 382:319 (1996); Spencer et al., Nature 389: 194 (1997)). Therefore, nuclear receptor recruitment of HAT activity at the place of their action supports the long held belief that the core histone acetylated modulation of the chromatin structure is involved in gene expression by sequence specific factors (Brownell et al., Curr. Opin. Genet. Dev. 6: 179 (1996), Wolffe et al., Cell 86:817 (1996) and Wade et al., Curr. Biology 7:R82 (1997)). Targeted acetylation of histone would melt nucleosomal cores but the question of histone HI removal remains unanswered. Since histone HI is a potent repressor of transcription by RNA polymerase II (Croston et al, Science 251:643 (1991); Laybourn et al. in Science 254:238 (1991)) which converts a 10 nm chromatin fibre to a more compact 30 nm, removal of HI histone from the chromatin appears obligatory for transcription. The HMG-I and HMG-Y proteins are non-histone chromosomal proteins which bind to A/T rich sequences in the minor groove of the DNA helix through a DNA binding motif called an "A.T hook" (Reeves et al., J. Biol. Chem. 265:8573 (1990); Nissen et al., J. Biol. Chem. 270:4355 (1995)). There are three A.T hook motifs present in the HMG-I sequence defined by arnino acids 21 -31 , 53-63 and 78-88, whereas HMG-R contains two A.T hook motifs defined by amino acids 21-31 and 53-63. It is generally accepted that linker histone HI is a repressor which plays a pivotal role in compaction of the chromatin into transcriptionally silent fibre (Zhao et al., EMBOJ. 12:3237 (1993); Davie, Int. Rev. Cytol. 162A:191 (1995)). Transcription activation involves the opening of the silent chromatin fibre through a reduction in the associated histone HI complement (Ericsson et al., Cell 60:73 (1990); Kamakaka et al., EMBO J. 9:3997 (1990)). It has been shown that HMG-I and HMG-Y proteins are able to displace HI from their binding sites present in the scaffold-associated regions (SAR) of the transcribed genes and can derepress the Hl-mediated inhibition of the SAR transcription (Zhao et al., EMBOJ. 12:3237 (1993)). Accordingly, HMG-I/Y is associated with the transcriptionally active HI -depleted chromatin (Zhao et al., EMBO J. 12:3237 (1993)) and present at high levels in proliferating, undifferentiated cancer cells as compared to their normal counterparts (Johnson et al., Exp. Cell Res. 187:69 (1990), Ram et al., Cancer Res. 53:2655 (1993), Chiapetta et al., Oncogene 10:1307 (1995); Fedele, et al., Cancer Res.56: 1896 (1996)). In accordance with its role in active transcription, HMG-I has been shown to interact with a number of transcription factors, namely, NF-κB, ATF-2, Elf-1, Oct-2, Oct-6/Tst-l and PU.l (Du et al, Cell 74:887 (1993), John et al. Mol Cell. Biol. 15:1786 (1995), Lewis et al. Mol Cell. Biol. 14:5701 (1994), Du et al., Proc. Natl. Acad. Sci. USA 91:11318 (1994), Nagulapalli et al, J. Immunol. 155:4330 (1995), Abdulkadir et al., J. Exp. Med. 182:487 (1995) and Leger et al., Mol. Cell. Biol. 15:3738 (1995)). A large number of chemical compounds has been shown to possess retinoid-like biological activity (see, for example, U.S. Patent Nos. 4,980,369, 5,006,550, 5,015,658, 5,045,551, 5,089,509, 5,134,159, 5,162,546, 5,234,926, 5,248,777, 5,264,578, 5,272,156, 5,278,318, 5,324,744, 5,346,895, 5,346,915, 5,348,972, 5,348,975, 5,380,877, 5,399,561, and 5,407,937, and patents and publications cited therein, the contents of each of which is incorporated herein be reference). Several retinoids have been approved for the treatment of certain dermatological disorders. All-trans retinoic acid (Retin A®) and 13- cw-retinoic acid (Accutane ® ), both naturally occurring retinoids metabolically derived from vitamin A, are marketed for the treatment of severe acne. Another naturally occurring retinoid that has received recent attention is 9-cw-retinoic acid. This isomer of all-trans retinoic acid has shown activity in several tumor models and promoted enhanced tumor sensitivity toward cϊs-platin in a human oral squamous cell carcinoma xenograft model (Shalinsky et al., Cancer Res. 2:511 (1996)). Clinical studies suggest that 9-cz ' s-retinoic acid, applied topically, is effective in the treatment of Kaposi's sarcoma lesions. Furthermore, 9-cw-retinoic acid administered p.o. has been shown to induce complete remission in patients with acute promyelocytic leukemia. Etretinate (Tegison™), an aromatic synthetic retinoid, is prescribed for severe refractory psoriasis. More recently, AGN 190168 (Tazorac™)(ethyl 6-[2-(4,4-dimethylthiochroman-6-yl)- ethynyl]nicotinate (Nagpal et al., Annual Reports of Medicinal Chemistry 32:201 (1997)), was approved by the FDA for the topical treatment of stable plaque psoriasis and facial acne vulgaris. Unfortunately, the use of retinoids as therapeutic agents has been limited due to undesirable side effects that accompany treatment with some such retinoids. These side effects can include skin irritation, visual effects (e.g. night blindness, dry eye), headache, mucocutaneous, lipid and bone toxicity, hepatotoxicity, and teratogenicity. Exceeding beneficial levels of retinoids can, in some cases, lead to hyperotarninosis A that can result in cornification disorder, alopecia and metabolic disorders. SUMMARY OF THE INVENTION The present invention relates to methods of identifying compounds which are modulators of nuclear receptors. According to one embodiment, the method comprises contacting a first polypeptide comprising a ligand binding region of the nuclear receptor with a test compound in the presence of a second polypeptide comprising a nuclear receptor-binding portion of an HMG protein. Altered binding of the first polypeptide with the second polypeptide in the presence of the test compound serves as an indication that the test compound is a modulator of the receptor. The contacting step may occur either in vivo or in vitro. Preferably, the polypeptides each further comprise a reporter tag whose interaction is directly or indirectly detectable when the first polypeptide and second polypeptide are bound. The reporter tag is, or comprises, a molecule such as a protein, nucleic acid or portion thereof, whose interaction with a second tag can be detected when the two tags interact or bind. In one embodiment, the reporter tag of either the first or second polypeptide comprises a DNA binding domain able to bind to a target nucleic acid upstream of a target gene, and the reporter tag of the other remaining polypeptide comprises an activation domain capable of stimulating transcription of the target gene. The target gene may be any gene which is able to directly or indirectly indicate the interaction of the reporter tags. The reporter tags may be, or be derived from, gene regulatory molecules, i.e., transcription factors. Preferably such reporter tags are derived from Gal-4, i.e., the activation and binding domains of Gal-4. The invention further provides polynucleotides encoding for the first polypeptide and second polypeptide. The invention also provides compounds identified by the methods described herein and, in particular, those compounds having a therapeutic effect such as anti-proliferative, anti-inflammatory, anti-psoriatic or anti-cancer cell growth effect. The invention also provides a method for identifying proteins which interact with an HMG protein comprising contacting a first polypeptide with a second polypeptide comprising a nuclear receptor-binding portion of an HMG protein either in the presence or absence of a hormone-like compound; and detecting binding of the first polypeptide with the second polypeptide as an indication that the protein physically interacts with the HMG protein. Such physical interaction may provide an indication that the protein regulates or is regulated by an HMG protein. As used herein, a "nuclear receptor" is a polypeptide capable of being bound by an HMG protein. Examples of such nuclear receptors are hormone receptors, including retinoid, steroid, glucocorticoid, thyroid, vitamin D and peroxisome proliferator receptors. Where the receptor is a retinoid receptor, preferably the retinoid receptor is a retinoic acid receptor selected from RAR- , RAR- and RAR- , and isoforms thereof. As used herein, a "modulator" is a compound capable of binding to a nuclear receptor whose binding affects the interaction or binding of an HMG protein to the nuclear receptor. As used herein, an "HMG protein" is HMG-I, HMG-R, HMG-Y/R or HMG-G, or an analog thereof. As used herein, a "hormone-like compound" is a compound capable of binding to a nuclear receptor or HMG protein, and affects the interaction or binding between the protein and receptor. An example of such hormone-like compound is (E)-4-[2-(5 ,6,7,8- tefrahydro-5,5,8,8-tetramemyl-2-napmlenyl)propen-l-yl]benzoic acid (TTNPB). The present invention further provides novel HMG proteins capable of interacting with retinoid receptors. BRIEF DESCRIPTION OF THE DRAWINGS Figures 1A shows ligand-dependent interaction of a RAR mutant having regions A and B deleted with fusion proteins containing HMG-I, HMG-R and Sugl. Figure IB shows an alignment of the amino acid sequences of HMG-I, HMG-Y, HMG-R, HMG-Y/R and HMG-G. Figure 1C shows the PCR amplification of nucleic acids from cDNA isolated from keratinocytes and skin rafts using HMG specific PCR primers. Figures 2A-2E are graphical representations showing the interaction of HMG-I and HMG-R with the wild type RAR and RAR truncation mutants in a yeast two- hybrid system. Figures 3A-3D are a series of bar graphs that show HMG interaction with nuclear receptors and cofactors other than RAR. Figure 4 shows the in vitro interaction of HMG-I with wild type RARs. Figure 5 is a schematic representation showing recruitment of CBP/p300 and HMGs and their targets in chromatin. Figure 6 is a schematic representation of an example of a two-hybrid assay which can be used in the method of the present invention to measure ligand interaction. DETAILED DESCRIPTION OF THE INVENTION The present invention provides novel HMG proteins that interact with RARs in a ligand dependent manner to induce gene expression. Additionally, the invention discloses that an HMG family member, HMG-I, interacts with RARs in a ligand dependent manner. HMG proteins including HMG-I, HMG-R, HMG-Y/R and HMG-G, interact with RARs in the presence of ligand. Thus, RARs are capable of recruiting not only histone acetyltransferase (HAT) and histone deacetylase activities but also HI displacement activities in a ligand specific manner. The present invention also provides a method for identifying compounds capable of modulating the activity of nuclear receptors. The method comprises contacting a first polypeptide comprising a ligand binding region of the nuclear receptor with a test compound in the presence of a second polypeptide comprising a nuclear receptor-binding portion of an HMG protein. Without being bound by any particular theory, it is believed that binding of the compound to the nuclear receptor causes a conformational change in the receptor which allows binding of the HMG protein to the receptor. A measurement or detection of the interaction indicates whether that compound is a modulator of the nuclear receptor. Alteration of binding includes both decreased and enhanced binding. Thus, the present method can be used to screen for compounds having a range of effects on HMG protein-receptor interaction, from agonistic to antagonistic. By using a known modulator, such as TTNPB, the method can be used to verify whether known nuclear receptors interact with HMG proteins in a ligand (hormone) dependent manner. In addition, using the same technique, novel receptors can be identified which interact with HMG proteins. As shown in the experiments described below, HMG-R appears to bind more strongly to TTNPB-stimulated RAR AB sequences than to RAR AB sequences, while HMG-I appears to bind more strongly to RAR AB sequences than to RAR AB. The present inventors have previously discovered that different retinoid ligands are able to stimulate a given retinoid receptor subtype and/or its isoforms to a greater or lesser degree. Thus, there are ligands that have a high degree of specificity for RAR, and do not appreciably stimulate RXR. Additionally, such ligands may stimulate RAR and not RAR , for example. It is therefore anticipated that a ligand will modulate the function of a given RAR subtype isoform while affecting other isoforms of the same RAR subtype to a lesser degree, if at all. Accordingly, the present invention additionally provides a method for the identification of ligands capable of modulating the activity of, and having a high degree of specificity for, a given nuclear receptor subtype or isoform of such a nuclear receptor subtype. This method comprises contacting a first polypeptide comprising a ligand binding region of a first nuclear receptor subtype and or isoform for which a modulating ligand is sought with a second polypeptide comprising a receptor binding portion of an HMG protein, and comparing the characteristics of binding between the first and second polypeptides with the characteristics of binding between the second polypeptide and at least one additional polypeptide comprising a ligand binding region of a different isoform or subtype of the same or different nuclear receptor. Ligands are identified which cause specific differences in these binding characteristics as an indication of specificity of the activity of the ligand as a modulator of the first nuclear receptor subtype and/or isoform. Any suitable means can be used to detect or measure the interaction between the HMG protein and the nuclear receptor. For example, the polypeptides may each further comprise a reporter tag which is directly or indirectly detectable when the first polypeptide and second polypeptide bind. In one embodiment, the reporter elements are transcription factor motifs associated with reporter genes. Advantage is taken of the fact that many eukaryotic trα/is-acting transcription factors comprise a DNA-binding domain sequence which binds to a DNA activation site, and an activation domain which stimulates transcription of a target gene. Both the DNA-binding domain and the activation domain are required to activate the gene. If physically separated by recombinant DNA technology and expressed in the same host cell, the domains do not directly interact with each other and thus do not activate the gene. However, if the DNA- binding domain and the activation domain are brought together into close proximity in a promoter region, the transcriptional activation function is restored. In a preferred embodiment, the transcription factor is the Gal-4 protein. The Gal-4 protein comprises an activation domain and a DNA-binding domain which binds to the regulatory sequences that determine expression of the -galactosidase gene. In practicing this particular embodiment, either the first or second polypeptide comprises either the DNA-binding domain or the activation domain. This polypeptide is capable of binding to an activation site upstream of a reporter gene. The other polypeptide comprises the remaining domain. In the presence of a modulator, the first and second polypeptides bind, bringing together the DNA-binding domain and activation domains of the reporter, and thus causing transcription of the reporter gene. Expression can be compared with a basal level to determine the effect of the test compound. One embodiment of this two-hybrid assay is shown in Figure 6. The LAC Z gene, which encodes for β-galactosidase, is transcriptionally responsive to binding of the Gal4 protein to the Gal4 responsive element (17 mer). The first polypeptide comprises the Gal4 DNA binding domain (DBD) and a retinoic acid receptor or other nuclear receptor (R). The second polypeptide comprises the Gal4 activation domain and HMG (either HMG-I or HMG-R). Binding of the first polypeptide alone to the 17 mer does not result in transcription (-). However, binding of the first and second polypeptides together, coupled with binding of the first polypeptide to the 17 mer results in transcription (+). The ability of a compound to induce nuclear receptor-HMG interaction-mediated basal expression of a reporter gene is typically measured in an in vitro assay. For example, where the reporter gene is the β-galactosidase gene, the measuring step may comprise use of a β-galactosidase assay. Basal expression represents the baseline level of nuclear receptor-HMG interaction-mediated reporter gene expression in transformed yeast cells in the absence of exogenous receptor agonist. If eukaryotic cells other than yeast cells are used, steps may be taken to remove endogenous ligands from the environment of the transfected cells via procedures such as charcoal extraction of the serum that is used to culture cells in vitro. Cells useful in connection with the screening method can be prokaryotic cells that are capable of being transfected. Eukaryotic cells that can be transfected may also be used. The eukaryotic cells may be yeast, insect or animal cells such as human, primate or rodent cells. Both CV-1 and HeLa cells are examples of useful cell lines, although it is expected that other cultured cell lines may also be used successfully. Any conventional transformation or transfection method known in the art can be used to introduce the expression construct. In a specific embodiment of the invention, a yeast two-hybrid system was used to identify and characterize complementary DNAs (cDNAs) that encode for proteins that interact with human RAR in a ligand dependent manner. The sequence of RAR encompassing the C to F regions (amino acids 90 to 454) was used as a "bait" to isolate cDNAs encoding interacting proteins from a HaCaT keratinocyte pooled cDNA library. The bait construct (pAS2-RAR AB) contained both the DNA binding domain (DBD) and the ligand binding domain (LBD) of RAR fused to the Gal4 DBD in a yeast expression vector pAS2-l. Stably transfected pAS2-RAR AB yeast cells were transformed with the second vector that expressed proteins comprising the Gal4 activation domain (AD) randomly fused in frame with members of the HaCaT keratinocyte library cDNA. Apart from the known RAR interacting proteins Sug 1 and RLP140, complete cDNAs were isolated for a high mobility group-I (HMG-I) protein and a novel HMG-I related protein designated HMG-R. Interaction in yeast cells was observed only when pAS2-RAR AB was expressed with HMG-I/HMG-R cDNA fused to the Gal4 AD. Neither pAS2-RAR AB nor pACT2-HMG-I/HMG-R were active when expressed alone. The ligand dependency of RARHMG interaction in vivo was examined and it was found that HMG-I and HMG-R proteins interacted specifically with RAR AB in the presence but not in the absence of the RAR agonist (E)-4-[2-(5,6,7,8-tetrahydro-5,5,8,8- tetramethyl-2-napthlenyl)propen-l-yl]benzoic acid (TTNPB). TTNPB is an RAR-specific synthetic retinoid which binds to RAR , and with Kd (nM) of 41, 6 and 44, respectively (Nagpal et al., J. Biol. Chem. 270: 923 (1995)). Figure 1 A represents the HMG-I and HMG-R interaction with RARγΔAB in yeast. The β-galactosidase activity of the interacting proteins HMG-I and HMG-R fused to the Gal4-AD (pACT2-HMG- I pACT2-HMG-R) in the Y190 yeast strain is shown. The activities of pAS2-RARγΔAB (bait construct alone) and the positive controls (pAS2-RARγΔAB and pACT2-Sugl) are also shown. Yeast cells were grown in selective media in the absence of TTNPB (denoted by open bars) or in the presence of TTNPB (1 μM)(denoted by solid bars). RAR AB interacted with both HMG-I and HMG-R in a dose dependent manner. Upon sequencing, HMG-R was found to be a variant of HMG-I having a deletion of a stretch of 67 nucleotides as compared to the HMG-I sequence. This deletion resulted in a frame shift so that the two proteins are identical in their first 65 amino acids from the amino terminals, but differ thereafter. An alignment of the putative amino acid sequence of HMG-R with those of HMG-I and another related member HMG-Y (Karlson et al., Biochem. Biophys. Res. Commun. 158: 646 (1989)) is shown in Figure IB. The numbers on me right correspond to total number of amino acids in a given HMG form. Italicized letters correspond to common amino acids which are shared between HMG-R and Y/R; and "_" denotes deletion of an amino acid. To prove that HMG-R exists in RNA samples other than the HaCaT cDNA library from where it was originally isolated, RT-PCR was performed on total RNA prepared from cultured keratinocytes and skin rafts (three-dimensional cultures of fibroblasts and keratinocytes) using primers directed to HMG-I 5' sequence and the 3' polyadenylation sequence. In addition to a major amplified fragment of 320 bp (HMG-I), two other minor amplified fragments of 250 bp (HMG-R) and 220 bp (HMG-Y R and HMG-G) were observed in all the samples as depicted in Figure IC (foreskin keratinocytes (lines 2 and 3), skin rafts (lane 4) and HaCaT library cDNA (lanes 1 and 5)). These fragments were purified and cloned into TA plasmids. The identity of these bands was confirmed by sequencing the TA-cloned PCR fragments. The HMG-Y R protein shows two deletions which are individually present in the amino acid sequence of HMG-Y and HMG-R. The amino acid deletions for HMG-Y, HMG-R, HMG-Y/R and HMG-G compared to HMG-I are represented by dotted lines in Figure IB. The HMG-G protein shows the HMG-Y/R deletions but shares the C-terminal amino acids with that of HMG-I (Figure IB). HMG-R, HMG-Y/R and HMG-G are novel forms which appear to be produced from the HMG-I/Y gene by alternative splicing using non-canonical splice donor and acceptor sites. To demonstrate that the full length RAR also interacts with HMG-I and HMG-R in a ligand dependent manner in vivo, yeast cells stably transformed with full length RAR (pAS2-RAR ) were further transformed with pACT2-HMG-I and pACT2-HMG-R and assayed for -galactosidase activity in the absence or presence of TTNPB. Full length RAR , by virtue of its activation functions known as AF1 and AF2 (Nagpal et al., EMBO J. 12:2349 (1993)), exhibited 10 units of -galactosidase activity in the presence of TTNPB, which was further induced to 270 and 255 units, respectively, in the presence of ρACT2-HMG-I and pACT2-HMG-R (Figure 2A)(open bars denote absence of TTNPB, solid bars denote presence of TTNPB). Both pACT2-HMG-I and pACT2-HMG-R also showed ligand dependent interaction with RAR and RAR , as shown in Figures 2B and 2C. β-Galactosidase activity is shown for yeast cells co- transformed with RAR mutant and either HMG-R (shown in Figure 2B) or HMG-I in the absence (denoted by open bars) or presence (denoted by solid bars) of TTNPB (1 μm). It is important to note that the full length protein RAR interacted more avidly with HMG-I and HMG-R compared to RAR AB, as shown in Figures 2B and 2C, thus lending even more weight to the argument that RAR and HMG naturally interact in vivo. To examine the regions of RARγ involved in the interaction with HMG-R in vivo, pAS2-RAR -DEF, pAS2-RAR AB and pAS2-RAR transformed yeast cells were used. pACT2-HMG-R interacted poorly with RAR DEF and RAR AB but showed robust activity with RAR (Figure 2D). These results demonstrate that the ligand binding domain (LBD), which is present in the E region of RAR, is not alone sufficient to permit RAR interaction with HMG, but that the A/B region transactivation function (AF-1) or ligand independent activation function (Nagpal et al., EMBO J. 12:2349 (1993)), also appears desirable for full interaction. Full length RAR interacted with both HMG-I and HMG-R in a dose dependent manner as shown in Figure 2E. Yeast cells were co- transformed with pAS2-RAR and pACT2-HMG-I (denoted by solid bars) or ρACT2- HMG-I (denoted by open bars). Similar dose-responsiveness was observed for the retinoid dependent induction of a number of endogenous single copy RA-responsive genes. Both HMG-I and HMG-R, in addition to RAR, also interacted with c-Jun (Figure 3A), PPAR (Figure 3B) and CREB-binding protein (CBP) (Figure 3C). CBP is a master regulator which is involved in signal transduction through a number of transcription factors (Glass et al., Curr. Opin. Cell Biol. 9:222 (1997)). Yeast cells were co- transformed with pAS2-Jun (Figure 3A), pAS2-PPARγl (Figure 3B), or pAS2-CBP (Figure 3C) along with ρACT2-HMG-I or pACT2-HMG-R. The β-galactosidase activity is shown to indicate the interaction between the HMGs and nuclear factors. In Figure 3B the HMG-I and HMG-R interactions are shown in the absence (denoted by open bars) or presence (denoted by solid bars) of PPARγl ligand. Taken together, it appears that transcription factors in general may recruit HMG-I to their place of action. Furthermore, although HMG-I interacts with CBP, it is not acetylated by either CBP or p300 as shown in Figure 3D. CBP or p300 antibodies were used to immunoprecipitate CBP (denoted by open bars) or p300 (denoted by solid bars) from HeLa cell nuclear extracts. The immune complexes were tested for their ability to acetylate BSA, free histones or HMG- I. To further characterize the RAR-HMG interaction observed in the yeast two-hybrid system, their association in vitro was studied. RAR antibodies were immobilized on protein A- and GSepharose® beads, and used for adsorbing bacculovirus-produced RAR. RAR beads were then mixed with 35 S radiolabeled in vitro translated Gal4-HMG-I in the presence or absence of TTNPB (1 μM), washed to remove non-specific binding, boiled to elute the bound protein and electrophoresed. The RAR antibody immunoprecipitated HMG-I in the presence and not in the absence of TTNPB (Figure 4). By contrast, treatment with IgG did not result in ligand-dependent immunoprecipitation. Similarly, the RAR antibody specifically immunoprecipitated HMG-I in a retinoid dependent manner (Figure 4). RARs and CBP both interact with HMGs in yeast as shown in Figures 1 A and 3C. Since HMG-I protein has 19 putative acetylation sites (lysine residues), including two in the DNA binding A.T hook domain (Figure IB), the acetylation of HMG-I by CBP/p300 would appear to decrease its ability to displace HI . In accordance with its role as a HI displacement factor, HMG-I was not acetylated by either CBP or p300 (Figure 3D). Therefore, in order to liberate the DNA from the nucleosome and to prevent the formation of compact higher order structures at the site of active transcription, both the chromosomal as well as the linker histones need to be released in a ligand dependent manner. The data indicates that RARs are capable of recruiting not only HATs but also the HI displacing activities of HMG-I and HMG-R in a targeted and ligand dependent manner as shown in Figure 5. Estrogen receptor and a number of other transcription factors other than the retinoid receptors are associated with the nuclear matrix (Davie, Int. Rev. Cytol. 162A:191 (1995) and Metzer et al., Endocrinol. 126:2190 (1990)). Therefore, the interaction of nuclear receptors simultaneously with a number of co-factors, namely, CBP/p300, ΗF1, TLF2/GRIP1, SRC-1, Sugl Tripl, RLP 140, HMG-I/HMG-R, etc., may form a nuclear matrix transactivation scaffold (MATS), capable of melting the core and the linker region of the nucleosome in a targeted ligand dependent manner. The RAR MATS may bind to an RARE, present in the upstream region of an RA-responsive gene, thereby preventing core and linker histone assembly and establishing transcriptionally competent chromatin structure for the formation of enhanceosomes and recruitment of RNA pol II transcription machinery. Although other materials and methods similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are now described. General references for methods that can be used to perform the various nucleic acid manipulations and procedures described herein can be found in Molecular Cloning: A Laboratory Manual (Sambrook et al., eds. Cold Spring Harbor Lab Publ. 1989) and Current Protocols in Molecular Biology (Ausubel et al., eds., Greene Pubhshing Associates and Wiley-Interscience 1987). The disclosures contained in these references are hereby incorporated by reference. A description of the experiments and results that led to the creation of aspects of the present invention follows. The following examples are intended to illustrate, and not limit, the present invention. EXAMPLES Example I - Plasmid construction In a yeast two-hybrid system, the bait (pAS2-RARγΔAB) consisted of the Gal4- DBD and the RARγ coding sequence spanning the C-F regions (amino acids 90 to 445). pAS2-RARγΔAB was constructed by PCR amplification and subsequently subcloning the amplified product into Eco RI-Bam HI sites of pAS2-l (Clontech, CA). pAS2-RARγ and pAS2-RARγDEF were prepared by PCR amplification of wild type (A-F regions) and D-F regions of RARγ, respectively. pAS2-RARαΔAB and pAS2-RARβΔAB were constructed by amplification of C-F regions of RARα (amino acids 88 to 462) and RARβ (amino acids 81 to 448 ). pAS2-Jun, was constructed by PCR amplification of wild type c-jun. PCR amplifications were performed using cDNAs (1 μg) in ready tubes containing buffer and nucleotides (Molecular Bio-Products, San Diego, CA) with the addition of Taq polymerase (1 μl, Perkin Elmer, Branchburg, NJ). For PCR amplification, DNA was denatured at 95°C for 5 minutes followed by 35 cycles of PCR with a temperature profile of 30 sec at 95°C, 30 sec at 60°C, 30 sec at 72°C. and a final cycle of 7 min at 72°C. The amplified products were resolved on an agarose gel (1%), stained with ethidium bromide and photographed. The amplified fragments were purified and cut with appropriate restriction enzymes, and again resolved on an agarose gel, purified using QLAquick (Qiagen Santa Clara, CA), ligated at 16 C overnight to the appropriate plasmids and transformed in E. coli. The plasmids were transformed in DH12S E. coli via electroporation at 1.66 Volts. The cells were grown on ampicillin plates overnight at 37 C. Colonies were picked, grown overnight in ampicillin medium, DNA was isolated using Wizard mini prep kit (Promega, Madison, Wl) and sequenced to verify the sequence and the reading frame. Primer pairs used for PCR amplifications were as follows: RARγ AB: 5'-AGGAATTCTGCTTCGTGTGCAATGACAAGT-3' (SEQ LDNO:l) and 5'-AGGGATCCTCAGGCTGGGGACTTCAGGCC-3' (SEQ LD NO:2) with EcoRI and BamHl cloning sites. RARα AB: 5'-AGGAATTCTGCTTTGTCTGTCAGGACAAGT-3' (SEQLDNO:3) and 5'-AGGGATCCTCACGGGGAGTGGGTGGCCGGG-3' (SEQ LD NO:4) with EcoRI and BamHl cloning sites. RARβ AB: 5'-AGCCCGGGGTGCTTCGTCTGCCAGGACAAATCAT-3' (SEQ ID NO:5) and 5 '-AGGGATCCTTATTGCAGGAGTGGTGACTGACTG-3 ' (SEQ LDNO:6) with Smal and BamHl cloning sites. RARγA-F: 5'-ACCGCAGGGATCCTGGCCACCAATAAGGAGCGA-3' (SEQ LD NO:7) and 5'-TAATGGATCCTGGTCAGGCTGGGGACTT-3' (SEQ LD NO:8) with BamHl and BamHl cloning sites. RARγDEF: 5'-TTCGAAGTGGAATTCTCCAAGGAAGCTGTG-3' (SEQJX>NO:9) and 5'-TAATGGATCCTGGTCAGGCTGGGGACTT-3' (SEQ LD NO:10) with EcoRI and BamHl cloning sites. cJun: 5'-AGGAATTCATGACTGCAAAGATGGAAACGACC-3' (SEQ ID NO:ll) and 5'-AGGGATCCTCAAAQATGTTTGCAACTGCTG-3' (SEQ LD NO: 12) with EcoRI and BamHl cloning sites. PPARγ: 5'-AGCATATGACCATGGTTGACACAGAGATC-3' (SEQ LD NO:13) and 5'-AGGTCGACCTAGTACAAGTCCTTGTAGATCTC-3' (SEQ LD NO:14) with Ndel and Sail cloning sites. CBP: 5'-AGAAGCTTATGGCCGAGAACTTGCTGGAC-3' (SEQ LD NO: 15) and 5 '-AGGGATCCCTAGGGTGCCAGCATGTTCAGAGGGTT-3 '(SEQ LD NO: 16) with HindLπ and BamHl cloning sites. Gal4-HMG-I was constructed by PCR amplification of HMG-I from pACT2-HMG-I using oligo primer pairs: 5'-AGCTCGAGCAATGAGTGAGTCGAGGCTCGAAGTCC-3' (SEQ LD NO: 17) and 5'-AGGGTACCTCACTGCTCCTCCTCCGAGGACTC-5'(SEQ LD NO:18). PCR amplified fragments were digested with Xho I and Kpn I and cloned in front of Gal4 DNA binding domain (amino acids 1-146 of Gal4) in a eukaryotic Gal4 DNA binding domain expression vector. Example II - Yeast Transformation. The bait plasmid pAS2-RARγ AB was transformed in yeast Y190 strain following yeast two-hybrid transformation procedure (Clontech, Palo Alto, CA). Briefly, Y190 cells (1 ml) grown overnight in YPD media were inoculated into 50 mis of YPD and further grown for 3-5 hours at 30°C to reach log phase (00 500 = approximately 1). Cells were pelleted at lOOOg for 5 minutes at room temperature, washed with water (25 ml), resuspended in 1.5 ml of TE lithium acetate buffer (10 mM Tris.HCl, pH 8.0; 1 mM EDTA, pH 8.0 and 100 mM lithium acetate) and aliquoted (50 μl) into eppendorf tubes. Each tube was used for a single transformation. For transformation, the aliquotted cells were pelleted and resuspended in 240 μl PEG, 36 μl of 1M LiAc, 60 μl water, 10 μg herring testis carrier DNA and 1 μg of pAS2-RARγ AB. The mixture was vortexed for 1 min and incubated at 42°C for 20 min. Transformed cells were pelleted, resuspended in 400 μl water and 200 μl plated on yeast-tryptophane selective media, followed by incubation in a 30°C incubator for 3 days. For the yeast two-hybrid screening, yeast strain Yl 90 containing pAS2-RAR AB was transformed with a HaCaT keratinocyte cDNA expression library in pACT2 expressing Gal4-AD chimeras using the same protocol described above. Human Keratinocyte Matchmaker cDNA library was purchased (Clontech, Palo Alto, CA) and amplified according to the GeneTrapper Protocol for semi-solid amplification of plasmid cDNA libraries (Life Technologies, Gaithersburg, MD). Briefly, E.coli containing HaCaT keratinocyte library (1.25 x 10 6 cDNA transformants) were inoculated in semi solid agar medium and incubated for 45 hours without disturbance, as described (Life Technologies, Gaithersburg, MD). Cultures were centrifuged (8000 rpm) for 20 minutes and the cells were subjected to DNA purification using Wizard Mega Prep kit (Promega, Madison, WI). The column purified DNA was further purified by standard cesium chloride plasmid banding. Transformation of yeast cells with the keratinocyte library DNA was performed as described (Gietz, R.D. and R.H. Schiestl, 1995, Methods in Molecular and Cellular Biology 5:255-269). Approximately, 600,000 double transformants were screened on medium lacking tryptophan, leucine and histidine (-leucine, -tryptophan, -histidine) containing 25 mM 3 amino- 1,2,4-triazole in the presence of 1 μM TTNPB. Positive clones were tested for β-galactosidase activity using two different methods. These were Colony lift assay and ONPG (orthonitrophenyl- -D-galactoside) liquid assay following the Clonetech protocol manual. Colonies that grew on selective media were streaked on fresh selective plates in the presence of the retinoid, six on each plate and grown for 3 days in a 30°C incubator. Cells were lifted on a Whattman #5 paper, submerged in liquid nitrogen for 10 sec, placed on a presoaked filter containing Z buffer (16.1 g Na 2 HPO 4 *7H 2 O (60 mM final); 5.5 g NaHPO HP (40 mM final) ; 0.75 g KC1 (10 mM final); 0.246 g MgSO 4 » 7H 2 O (1 mM final); adjust to pH 7.0 and bring to 1 liter with distilled water (do not autoclave)) and Xgal (5-Bromo-4-chloro-3-indolyl- -D- galactoside)(Clonetech, Palo Alto, CA) and incubated at 30°C (10 min to 1 hour). Colonies containing interacting proteins turn blue. Cells that were positive in lift assay were grown in 5 ml (-leucine, -tryptophan, -histidine) medium overnight at 30°C. Overnight cultures (2 ml) were inoculated in fresh YPD media (8 ml) in the presence or absence of TTNPB, grown for 5 hours at 30°C and OU 600 recorded. The OD of the cells was measured in mid-log phase (0.5-0.8). Cells (1 ml) were pelleted, washed in 1 ml Z buffer and resuspended in 100 μl Z buffer. Cells were lysed by freezing in liquid N 2 for 1 min and thawed at 37°C for 1 min. Z buffer (700 μl) containing β-mercaptoethanol was added, followed by addition of 4 mg/ml ONPG (160 μl) as a substrate for β-galactosidase and the mixture incubated at 30°C for 5 min-1 hour (or until yellow color appeared). The reaction was stopped by the addition of 1M Na 2 CO 3 (400 μl) and tubes were spun for 10 min in a microcentrifuge to pellet debris. The supernatant (1 ml) was transferred to a cuvette and OD 420 was recorded, β- Galactosidase activity was calculated using the formula, 1000 x OD 42 o/time(min) x OD^ Interacting protein cDNA in expression vector pACT2 was selected by growing positive colonies on cyclohexamide-leucine selective plates as described in the Matchmaker Two- hybrid System 2 manual (Clonetech, Palo Alto, CA). Plasmid DNA was purified from yeast and transformed into E. coli. Plasmid DNA was isolated from E.coli cells, sequenced and the sequences were tested for homology against the Genebank sequences using the BLAST algorithm. Yeast strains, HaCaT keratinocyte library and yeast media were all purchased (Clonetech, Palo Alto, CA). Example III - HMG Amplification PCR amplification of HMGs: RT-PCR was performed using 0.5 μg mRNA from keratinocyte library, skin rafts, and cultured keratinocytes using the primers pairs: 5'- AGGGTACCATGAGTGAGTCGAGCTCGAAGTCC-3' (SEQ LD NO:19) and 5'-AGAAGCTTTCACTGCTCCTCCTCCGAGGACTC-3' (SEQ LD NO:20) encompassing HMG-I from the ATG start codon to the TGA stop codon. Ready tubes containing buffer and nucleotides (Molecular Bio-Products, San Diego, CA) with the addition of Taq polymerase (1 μl, Perkin Elmer, Branchburg, NJ). For PCR amplification, DNA was denatured at 95°C for 5 minutes followed by 35 cycles of PCR with a temperature profile of 30 sec at 95°C, 30 sec at 60°C, 30 sec at 72°C. and a final cycle of 7 min elongation at 72°C. The amplified products were resolved on a 4% Nusieve® gel, stained with ethidium bromide and photographed. DNA containing bands from the amplified keratinocyte library lane were excised and gel purified. DNA was cloned in a TA cloning pCRTMII vector (Invitrogen, San Diego, CA). The plasmids were transformed in DH12S E. coli (Life Technologies, Gaithersberg, MD) by electroporation at 1.66 volts. The cells were grown on ampicillin plates overnight at 37°C. Colonies were picked and grown overnight in ampicillin medium. DNA was isolated using Wizard mini prep kit (Promega, Madison, WT) and sequenced. Example IV - Histone Acetyltransferase (HAT) Activity. CBP or p300 antibodies (Santa Cruz Biotechnology, Santa Cruz, CA) were added to HeLa cell nuclear extract (Life Technologies, Gaithersberg, MD) and incubated at 4°C for 2 hours. Protein A/G-sepharose (1:1 mix, 25 μl; Sigma, St. Louis, MO) was added and the tubes rotated overnight at 4°C. Immunoprecipitated CBP or p300 were pelletted and washed three times with 1 ml of lysis buffer (50 mM Tris-HCl, pH 8.0, 150 mM NaCl, 0.5 % NP-40, 0.1 mM PMSF (phenylmethylsulfonyl fluoride), aprotinin and leupeptin). After the final wash, 25 μl of lysis buffer was added along with 1 μl BSA (bovine serum albumin), histones (Sigma, St. Louis, MO) or HMG-I (10 μg) and 1 ml of 3 H-acetyl CoA (NEN Life Science Products, Boston, MA) and incubated at 30°C for 45 min. Acetylation was quantitated using P-81 filters as described (Horiuchi, K. and Fujimoto, D., Analytical Biochemistry 69:491-496, 1975). HMG-RAR interaction in vitro. Bacculovirus-produced RARα or RARγ were immunoadsorbed on protein A/G-sepharose beads (1:1 mix, 10 μl; Sigma, St. Louis, MO) using RARα or γ antibodies (Santa Cruz Biotechnology, Santa Cruz, CA). Gal4-HMG-I plasmid was constructed as described above. 35 S labeled Gal4-HMG-I fusion protein was synthesized by in vitro transcription and translation in rabbit reticulocyte lysate (Promega, Madison, WI) following manufacturer's instructions. 35 S labeled Gal4-HMG-I (5 μl) was incubated with immobilized RAR protein in a total volume of 25 μl LPAB buffer (150 mM KCl, 0.1% Triton , 0.1% NP40, 0.02 mg/ml BSA, 20 mM HEPES, pH 7.9, 5 mM MgCl 2 lug/ml Leupeptin, lug/ml Aprotinin) in the presence of TTNPB (1 μM) or acetone control for 1 hr. After washing three times with LPAB buffer, the labeled proteins were resuspended in 25 μl SDS loading buffer and analyzed on SDS/PAGE gel. Images of labeled bands were visualized on a phosphorimager.

Claims: We claim: 1. A method for identifying a compound which is a modulator of a nuclear receptor comprising the steps: a) contacting a first polypeptide comprising a ligand binding region of said nuclear receptor with a test compound in the presence of a second polypeptide comprising a nuclear receptor-binding portion of an HMG protein; and b) detecting altered binding of said first polypeptide with said second polypeptide in the presence of the test compound as an indication that the test compound is a modulator of the receptor. 2. The method of claim 1 wherein said contacting step occurs in vivo. 3. The method of claim 2 wherein said first polypeptide and said second polypeptide each further comprise reporter tags whose interaction is directly or indirectly detectable when said first polypeptide and said second polypeptide are bound. 4. The method of claim 3 wherein the reporter tag of either said first or said second polypeptide comprises a DNA binding domain able to bind to a target nucleic acid upstream of a target gene, and the reporter tag of the other remaining polypeptide comprises an activation domain capable of stimulating transcription of the target gene. 5. The method of claim 4 wherein said reporter tags are derived from Gal-4. 6. The method of claim 1 wherein the nuclear receptor is selected from a retinoid, steroid, glucocorticoid, thyroid, vitamin D and peroxisome proliferator receptor. 7. The method of claim 6 wherein the nuclear receptor is a retinoid receptor. 8. The method of claim 7 wherein the retinoid receptor is a retinoic acid receptor. 9. The method of claim 8 wherein the retinoic acid receptor is selected from RAR- , RAR- and RAR- , and isoforms thereof. 10. The method of claim 1 wherein said contacting step occurs in vitro. 11. The method of claim 1 wherein the HMG protein is HMG-I, HMG-R, HMG-Y/R or HMG-G. 12. The method of claim 1 wherein the nuclear receptor-binding portion of the HMG protein is RAR AB. 13. A polynucleotide encoding for the second polypeptide of claim 12. 14. A compound identified according to the method of claim 1. 15. A compound identified according to the method of claim 1 having anti- proliferative, anti-inflammatory, anti-psoriatic or anti-cancer cell growth effect. 16. A method for identifying proteins which interact with an HMG protein comprising the steps: a) contacting a first polypeptide with a second polypeptide comprising a nuclear receptor-binding portion of an HMG protein, in the presence or absence of a hormonelike compound; and b) detecting binding of said first polypeptide with said second polypeptide as an indication that the protein physically interacts with the HMG protein. 17. The method of claim 16 wherein the hormone-like compound is TTNPB . 18. The method of claim 16 wherein said contacting step occurs in vivo. 19. The method of claim 16 wherein said first polypeptide and said second polypeptide each further comprise reporter tags which are directly or indirectly detectable when said first polypeptide and said second polypeptide are bound. 20. The method of claim 19 wherein the reporter tag of either said first or said second polypeptide comprises a DNA binding domain able to bind to a target nucleic acid, and the reporter tag of the other remaining polypeptide comprises an activation domain capable of stimulating transcription of said target gene. 21. The method of claim 20 wherein said reporter tags are derived from Gal-4. 22. A method of identifying ligands capable of specifically modulating the activity of a subtype of a nuclear receptor comprising: (a) contacting a first polypeptide comprising a ligand binding region of a first nuclear receptor subtype with a second polypeptide comprising a receptor binding portion of an HMG protein; (b) comparing the characteristics of binding between said first and second polypeptides with the characteristics of binding between said second polypeptide and at least one additional polypeptide comprising a ligand binding region of a different subtype of the nuclear receptor; and (c) identifying ligands causing differences in the binding characteristics of said first and second polypeptide compared to said second polypeptide and said at least one additional polypeptide as an indication of the specificity of the activity of said ligand. 23. A method of identifying ligands capable of specifically modulating the activity of an isoform of a nuclear receptor comprising (a) contacting a first polypeptide comprising a ligand binding region of a first nuclear receptor isoform with a second polypeptide comprising a receptor binding portion of an HMG protein; (b) comparing the characteristics of binding between said first and second polypeptides with the characteristics of binding between said second polypeptide and at least one additional polypeptide comprising a ligand binding region of a different isoform of the nuclear receptor; and (c) identifying ligands causing differences in the binding characteristics of said first and second polypeptide compared to said second polypeptide and said at least one additional polypeptide as an indication of the specificity of the activity of said ligand. 24. A polypeptide substantially comprising the sequence of SEQ ID NO: 23. 25. The polypeptide of claim 24 having specific binding affinity for a retinoic acid receptor. 26. The polypeptide of claim 25 having specific binding affinity for RAR- , RAR- or RAR- , or isoforms thereof. 27. A polynucleotide sequence which encodes the polypeptide of claim 24. 28. A polypeptide substantially comprising the sequence of SEQ LD NO: 24. 29. The polypeptide of claim 28 having specific binding affinity for a retinoic acid receptor. 30. The polypeptide of claim 29 having specific binding affinity for RAR- , RAR- or RAR- , or isoforms thereof. 31. A polynucleotide sequence which encodes the polypeptide of claim 28. 32. A polypeptide substantially comprising the sequence of SEQ ID NO: 25. 33. The polypeptide of claim 32 having specific binding affinity for a retinoic acid receptor. 34. The polypeptide of claim 33 having specific binding affinity for RAR- , RAR- or RAR- , or isoforms thereof. 35. A polynucleotide sequence which encodes the polypeptide of claim 32.

Inventors: CHANDRARATNA ROSHANTHA A, GHOSN CORINE, NAGPAL SUNIL, CHANDRARATNA, ROSHANTHA, A., GHOSN, CORINE, NAGPAL, SUNIL
Applicants: ALLERGAN SALES INC, ALLERGAN SALES, INC.
Application year: 1999
Main classification: C07K14
IPC codes: C07K14, G01N33