Material and methods for the production of a heterodimeric human LH with a Met42 Val55 alpha subunit

Abstract: Recombinant DNA technology allows biologically active post-translationally modified (for example glycosylated), proteinaceous hormones, such as human chorionic gonadotropin and leutinizing hormone, to be prepared free of any other such hormones and in single isoforms. Variation in hormonal specific activity from preparation to preparation can be eliminated.

Description: Background of the Invention This invention relates, inter alia, to the use of recombinant DNA techniques to produce luteinising hormone (LH). Various polypeptide chains have been expressed, via recombinant DNA technology, in host cells such as bacteria, yeast, and cultured mammalian cells. Fiddes, J. C. and Goodman, H. M. (1979) Nature Vol. 281, pg. 351-356 and Fiddes, J. C. and Goodman, H. M. (1980) Nature Vol. 286, pg. 684-687 describe the cloning of, respectively, the alpha and beta subunits of human choriogonadotropin (hCG). Kaname US Pat. 4,383,036 describes a process for producing hCG in which human lymphoblastoid cells are implanted into a laboratory animal, harvested from the animal, and cultured in vitro ; accumulated hCG is then harvested from the culture. Summary of the Invention According to the present invention there is provided a protein which is biologically active, post-transitionally modified, luteinising hormone (LH) having an α and β subunit, the β subunit being 121 amino acids in length and having the residues Met 42 and Val 55 . The protein may be produced by a process as described in any of claims 16 to 24. It may be present in a pharmaceutical composition together with a carrier and can be used in medicine. The pharmaceutical composition can be prepared as set out in claim 32. In preferred embodiments, the protein is synthesized by a eukaryotic cell and the protein is modified post-translationally, most preferably by glycosylation. The present invention also provides a DNA molecule comprising a DNA sequence encoding luteinising hormone (LH) having an α and β subunit, the β subunit having the residues Met 42 and Val 55 . The present invention further provides an expression vector capable of transfecting a eukaryotic cell, the vector comprising heterologous DNA encoding the α and β subunits of biologically active, post-translationally modified luteinising hormone (LH), the β subunit being 121 amino acids in length and having the residues Met 42 and Val 55 . Preferred expression vectors are described in claims 3 to 6. A set of expression vectors may be provided, as described in claims 7 to 9. The expression vectors can be prepared as described in claim 29 or claim 30. There is also provided a eukaryotic cell transfected with one or more expression vectors, the cell being capable of producing biologically active post-translationally modified luteinising hormone (LH) having α and β subunits, the β subunit of LH being 121 amino acids in length and having the residues Met 42 and Val 55 , the subunits of the LH being encoded by heterologous DNA in the expression vector(s). Preferred eukaryotic cells are described in claims 11 to 15. The eukaryotic cells can be prepared as set out in claim 31. As used herein, "subunit" refers to a portion of a protein, which portion, or homologue or analogue thereof, is encoded in nature by a distinct in mRNA. Thus, for example, a heavy chain and a light chain of an IgG immunoglobulin are each considered a subunit. Insulin, on the other hand, is composed of two chains which are not considered subunits, because both are, in 5 nature, encoded by a single mRNA, and cleavage into two chains naturally occurs only after translation. The term "expression vector" refers to a cloning vector which includes heterologous (to the vector) DNA under the control of control sequences which permit expression in a host cell. Such vectors include replicating viruses, plasmids, and phages. The invention permits the production of biologically active luteinising hormone from a single culture of transformed cells. The production of both subunits of a luteinising hormone in the same cell eliminates the necessity of recombining subunits from separate cultures to assemble an active heteropolymeric molecule. The system also allows production of luteinising hormone in a single culture, which undergoes, in the culture, post-translational modification, e.g. glycosylation and proteolytic processing, for activity or stability. The use of autonomously replicating expression vectors prevents undesirable influence of the desired coding regions by control sequences in the host chromosone. Other advantages and features of the invention will be apparent from the following description of the preferred embodiments thereof, and from the claims. Description of the Preferred Embodiments We turn now to the preferred embodiments of the invention, first briefly describing the drawings thereof. (Where drawings are not in respect of the invention as such, they are provided for information purposes.) Drawings Fig. 1 is a diagrammatic illustration of the construction of the plasmid p alpha SVHVP1, which contains the alpha hCG cDNA clone, portions of SV40 viral DNA, and sequences of the plasmid pBR 322. Fig. 2 is a diagrammatic illustration of the construction of plasmid p beta SVVP1, which incorporates the beta hCG cDNA clone, regions of SV40 DNA and a portion of pBR 322 including the region conferring resistance to ampicillin on host E. coli . Fig. 3 is a diagrammtic illustration of the construction of the plasmid p alpha beta SVVP1 in which the alpha and beta hCG cDNA clones are inserted into SV40 DNA. Fig. 4 is a diagrammtic illustration of the construction of the plasmids pRF375 and pRF398. Fig. 5 is a diagrammatic illustration of the construction of the plasmid RF398 alpha t 2 . Fig. 6 is a diagram illustrating the location of an 88 bp probe within the beta hCG cDNA clone. Fig. 7 illustrates the beta LH restriction map, and the pieces used in the construction shown in Fig. 8. Fig. 8 is a diagrammatic illustration of the construction of a plasmid, LH520H/B, containing the complete mature beta LH cDNA clone. Fig. 9 is a diagrammatic illustration of the construction of the viral vector p alpha LHSVVP1. Fig. 10 is a diagrammatic illustration of the construction of the BPV-containing plasmid pCL28XhoLHBPV, encoding the beta subunit of LH. Structure The cloning vectors of the invention have the general structure recited in the Summary of the Invention, above. Preferred vectors have the structures shown in the Figures, and are described in more detail below. Construction of Cloning Vectors Isolation of cDNA Clones Encoding the Alpha and Beta Subunits of hCG All of the techniques used herein are described in detail in Maniatis et al. (1982) Molecular Cloning: A Laboratory Manual (Cold Spring Harbor Laboratory), hereby incorporated by reference. RNA is extracted from placental tissue by the following method. Homogenization of the tissue is carried out in a 1:1 mixture of phenol:100mM Na-acetate (pH 5.5) containing 1mM EDTA, that has been warmed to 60 o for 20 min. After cooling on ice for 10 min., the phases are separated by centrifugation. The hot phenol extraction is repeated twice more followed by two extractions with chloroform. RNA is precipitated from the final aqueous phase by the addition of 2.5 volumes of ethanol. In order to enrich for poly A+ mRNA, placental RNA is passed over oligo (dT)-cellulose in 0.5M NaCl buffered with 10mM Tris-Hcl, pH 7.5, and washed with the same solution. Poly A+ mRNA is eluted with 10mM Tris-HCl (pH 7.5), 1mM EDTA, 0.05% SDS and precipitated twice with ethanol. Typical initial yields are 1.5-2.0 mg of total RNA per g of tissue, of which about 2% is poly A+ mRNA. Placental cDNA libraries are constructed by reverse transcription of placental mRNA, second strand synthesis using E. coli DNA polymerase I (large fragment), treatment with SI nuclease, and homopolymer tailing (dC) with terminal deoxynucleotidyl transferase; all such procedures are by conventional techniques. In a typical preparation, 20-30% conversion of mRNA to single strand (ss) cDNA; 70% resistance to digestion with nuclease Sl after second strand synthesis; and dC "tails" of ten to twenty-five bases in length, are obtained. These cDNA molecules are then annealed to DNA fragments of the plasmid pBR 322, which has been digested with Pst I, and to which dG "tails" have been added. These recombinant plasmids are then used to transform E. coli cells to generate a cDNA library (transformed cells are selected on the basis of tetracycline resistance). In order to identify the human alpha hCG clone, a 219 bp fragment of a mouse alpha thyroid stimulating hormone (TSH) clone is used as a hybridization probe. This probe has 77% sequence homology with the human clone. It is radioactively labeled by nick translation and hybridized to the cDNA library under conditions that take into account the extent of homology. Strongly hybridizing clones are analyzed by restriction mapping and clones containing the complete coding sequence of alpha hCG are verified by DNA sequencing. Construction of Plasmid p alpha SVHVP1 Referring to Fig. 1, in order to construct the plasmid alpha 970 H/B, a cDNA clone containing the alpha hCG fragment is digested with NcoI . The NcoI site, just 5' to the ATG codon signalling initiation of translation, is filled in and ligated to a synthetic Hind III linker. Similarly, the natural Hind III site in the 3' untranslated region of the clone is cut, filled in with E. coli DNA polymerase Klenow, and then ligated to a synthetic Bam HI linker. This fragment is cloned into the plasmid pBR 322 between its Hind III and Bam HI sites to generate the plasmid alpha 574 H/B. This plasmid is digested with Bam HI, treated with alkaline phosphatase, and ligated to the 396 bp Sau 3A fragment of SV40 DNA (from 0.07 to 0.14 map units) which has been isolated from a polyacrylamide gel. The ligation mix is used to transform E. coli to ampicillin resistance and the desired plasmid, alpha 970 H/B, is identified among the transformants. The plasmid Q 2 7 is constructed by cutting SV40 at its Hpa II site, making flush ends by digestion with nuclease Sl, ligating on Eco RI linkers, digesting with Eco RI, and cloning the resulting 1436 bp fragment into the Eco RI site of pBR 322. Referring to Fig. 1, Q 2 7 is digested completely with Eco RI and partially with Hind III; the fragment from 0.72 to 0.94 map units is isolated and cloned into alpha 970 H/B, which has been digested with Eco RI and Hind III and treated with alkaline phosphatase. The ligation mix is used to transform E. coli , and the desired plasmid, p alpha SVL, is identified among the transformants by restriction mapping. p alpha SVL is digested with Eco RI and the fragment of SV40, with Eco RI ends, extending from 0 to 0.72 map units, and containing the SV40 origin of replication and the intact early region, is ligated to it to generate the plasmid p alpha SVHVP1, which is isolated from E. coli transformants. Construction of Plasmid p beta SVVP1 A 579 bp cDNA clone coding for beta hCG was obtained from John C. Fiddes at Cold Spring Harbor Laboratory, Cold Spring Harbor, New York (Fiddes et al (1980) Nature Vol. 286, pg. 684-687). T is fragment is ligated at each end to synthetic Bam HI linkers. After digestion by Hga I restriction enzyme, the ends are filled in with Klenow DNA polymerase and synthetic Eco RI linkers are ligated on so that an Eco RI site is about 10 bp 5' to the ATG codon of the signal peptide coding sequence. A Bam HI site is about 60 bp 3' to the nonsense codon marking the end of the coding sequence. Referring to Fig. 2, this 556 bp Eco RI- Bam HI fragment is isolated and cloned into pBR 322, between the Eco RI and Bam HI sites, to give the plasmid p beta 556 R/B. In order to construct the plasmid pSVHR (Fig. 2), SV40 DNA is partially digested with Hind III to yield linear molecules, digested with nuclease S1 to make flush ends, ligated to synthetic Eco RI linkers and digested with Eco RI and Bam HI. The fragment from 0.94 to 0.14 map units, containing the SV40 origin of replication and early region, is cloned into pBR 322 as an Eco RI- Bam HI piece. Referring still to Fig. 2, the Eco RI site of the plasmid p beta 556 R/B is methylated in a reaction catalyzed by Eco RI methylase, following which the plasmid is cut with Nde I. Eco RI linkers are ligated to the SI treated Nde I flush ends and activated by digestion with Eco RI, which is followed by digestion with Bam HI. The SV40 fragment of pSVHR from the Eco RI site to the Bam HI site is isolated and ligated in a reaction mix containing the digestion fragments of p beta 556 R/B. Following ligation, the mix is digested with Sal I to eliminate plasmids which have re-inserted the Eco RI ( Nde I) to Bam HI piece of pBR 322. E. coli is transformed with the digested ligation mix and p beta SVVP1 is identified and isolated. Construction of the Plasmid p Alpha Beta SVVP1 Referring to Fig. 3, pBR 322/Kpn is derived from pBR 322 by inserting a Kpn I linker into its unique Eco RI site, after this site is deleted by digestion with Eco RI, followed by digestion with Sl nuclease. Referring still to Fig. 3, SV40 DNA is digested with Ava II. The staggered ends of the resulting fragments are filled in by Klenow DNA polymerase to form flush ends, and the mixture is then fractionated on a polyacrylamide gel. The 682 base pair fragment (0.64 to 0.77 map units) containing the origin of replication and the unique Kpn I site is isolated from the gel, ligated to synthetic Hind III linkers, and digested with Hind III and Kpn I. The resulting fragments are ligated to pBR 322/Kpn. p266, which contains the 266 base pair Kpn I - Hind III fragment, including the SV40 late promoter region, is isolated. p266 is cut with Hind III and Bam HI, and treated with bacterial alkaline phosphatase. Still referring to Fig. 3, p beta SVVPI/B is constructed as follows: p beta SVVPI (Fig. 2) is cut with Eco RI, followed by ligation to eliminate pBR 322 sequences. Subsequently, this DNA is cut with Bam HI and cloned into the Bam HI site of pBR 322. The resulting plasmid, p beta SVVPI/B, is then digested with Hind III and Bam HI and the 1003 base pair Hind III- Bam HI fragment is ligated into p266 to yield the plasmid p beta VP1 266, in which the beta hCG cDNA is positioned downstream from the SV40 late promoter in such a way that its RNA transcript would be spliced as if it were the viral VP1 transcript. The alpha hCG cDNA is inserted into p beta VP1 266 as a Hind III fragment, which has been cut at its Hind III site and treated with bacterial alkaline phosphatase. E. coli transformants derived from this ligation are screened by restriction mapping, and plasmids are isolated that have the desired structure, in which the alpha hCG cDNA has replaced VP2 in the correct orientation, followed downstream by the beta hCG cDNA, which has replaced VP1. One such isolated plasmid, p alpha beta VP1, is used to complete the construction of p alpha beta SVVP1. The plasmid is cut with Kpn I, and the full SV40 genome, cut with Kpn I, is inserted by ligation into this site. Following transformation of E. coli , a plasmid with the required structure, p alpha beta SVVP1, is isolated. This plasmid contains DNA encoding both the alpha and beta subunits of hCG, and thus is capable of directing the expression, in host mammalian cells, of both subunits, whereby biologically functional, glycosylated heterodimeric hCG is produced (glycosylation occurs post-translationally). Construction of Plasmids pRF 375 and pRF 398 Referring to Fig. 4, the plasmid CL28 (identical to plasmid JYMMT(E); Hamer et al. (1983) J. Mol. Applied Gen. 1 , 273-288), containing the murine metallothionein promoter, SV40 DNA, and pBR 322 sequences, is cut with the restriction endonuclease Bgl II. At this site are inserted cDNA clones of either alpha hCG or beta hCG, containing untranslated regions of about 10 and 30 bp at their 5' and of about 220 and 60 bp at their 3' ends. These clones have been genetically engineered by the addition of synthetic Bam HI linkers at their termini. The resulting plasmids pRF 302 (alpha) or pRF 394 (beta) are digested with restriction enzymes Bam HI and Sal I to release the SV40 DNA sequences. Plasmid pB2-2, which contains the entire BPV genome, and some pBR 322 sequences, is digested with Bam HI and Sal I to yield the BPV genome with Bam HI/ Sal I ends; this fragement is ligated into pRF 302 (alpha) and pRF 394 (beta) containing the metallothionein-hCG sequences. Following transformation of E. coli , plasmids pRF 375 and pRF 398 are identified and isolated. They encode alpha hCG or beta hCG, respectively, under the control of the mouse metallothionein promoter. Construction of the Plasmid RF 398 alpha t 2 Referring to Fig. 5, the plasmid p alpha t2 is derived by cloning the alpha hCG 574 Hind III fragment into plasmid pVBt2 (V.B. Reddy et al., PNAS 79 , 2064-2067, 1982). p alpha t2, which contains the alpha hCG cDNA under the control of the SV40 early promoter, is digested with Eco RI. The 5' overhangs are removed by Sl nuclease digestion prior to the addition of synthetic Bam HI linkers by blunt end ligation. Plasmid RF 398 (Fig. 4) is digested with Bam HI and treated with bacterial alkaline phosphatase. The 1735 base pair Bam HI fragment of p alpha t 2 is inserted in to RF 398. The resulting plasmid RF 398 alpha t 2 is isolated from E. coli transformants. This plasmid thus has the beta hCG cDNA in a transcriptional unit under control of the mouse metallothionein promoter and the alpha hCG cDNA in a transcriptional unit controlled by the SV40 early promoter. Expression of Luteinizing Hormone (LH) cDNA Clones Construction of a Human Pituitary cDNA Library RNA is prepared from human pituitaries by homogenizing 5 to 10 grams of the frozen glands in 20 ml of a solution containing 4 M guanidine thiocyanate, 1 M 2-mercaptoethanol, 0.05 M Na-acetate (pH 5.0), and 0.001 M EDTA. One g CsCl is added per ml of homogenate and the suspension is centrifuged at 2,000 rpm for 15 min. The supernatant is layered carefully over a 15 ml cushion of CsCl solution (containing 1.25 ml of 1 M Na-acetate (pH 5), 62.5 microliters of 0.4 M EDTA and 39.8g of CsCl in a final volume of 35 ml) and centrifuged at 45,000 rpm in the Ti 70 rotor of a Beckman ultracentrifuge for 18-24 h at 20°C. The RNA visible as a pellicle in the gradient is removed with a syringe, diluted, and precipitated by the addition of two volumes of ethanol. Following three cycles of dissolution and reprecipitation, the RNA pellet is dissolved in H 2 O and brought to 0.01 M Tris-HCl (pH 7.5) and 0.5 M NaCl by the addition of concentrated stock solutions. The preparation is then enriched for poly A + mRNA by two passes over oligo dT-cellulose, as described above in the case of placental RNA. A human pituitary cDNA library is constructed from the poly A + mRNA as described above for placental poly A + mRNA except that both the large fragment E. coli DNA polymerase I and the avian myeloblastosis virus reverse transciptase are used sequentially for second strand cDNA synthesis. The Klenow is used first. The reaction is stopped by phenol extraction. The aqueous phase of the centrifuged extract is applied to a 5 ml column of BioGel A-5m. Fractions containing high molecular weight material are pooled, concentrated, precipitated with two volumes of ethanol, dried, and dissolved in 100 mM Tris-HCl (pH 8.3), 10 mM MgCl 2 , 140 mM KCl, 20 mM 2-mercaptoethanol, 1 mM of each of the four deoxyribonucleoside triphosphates, for reverse transcription. Reverse transcriptase is added to about 20 units per microgram of cDNA. Double stranded cDNA is then treated with nuclease Sl, tailed, and cloned as described above. Isolation of Beta LH cDNA Clones Colonies grown on nutrient agar plates containing 25 micrograms per ml of tetracycline are transferred to nitrocellulose filters. Colonies are lysed in situ by treatment with 0.5 M NaOH and neutralized with 0.5 M Tris-HCl (pH 7.4) containing 1.5 M NaCl. Liberated DNA is fixed to the filter by baking at 80°C in a vacuum oven for 2 h. The filters are screened by hybridization to a 32 P labeled 88 base pair fragment of the beta hCG clone corresponding to amino acids 16 to 45 of the mature hCG beta chain, which has 29 of 30 amino acids in common with this region of the beta LH polypeptide (Fig. 6). Hybridization is carried out overnight at 32° in 50% formamide, 0.75 M NaCl, 0.075M Na-Citrate (pH 7.0), 2.5% dextran sulfate, 0.1% polyvinylpyrollidone, 0.1 mg per ml bovine serum albumin, and at least 10 5 cpm per filter of 32 P-labeled 88 bp beta hCG fragment. Filters are washed several times in 0.15 M NaCl, 0.015 M Na-citrate at 37°C before autoradiography. One of the positive isolated clones LH12 (Figure 7), is used further. LH12 is 365bp long and includes sequences coding for 15 amino acids of the pre-beta signal sequence plus 105 amino acids of the mature beta LH polypeptide. Its nucleotide sequence is determined. Since the complete mature beta LH is not coded by LH12, further screening of the human pituitary cDNA library is carried out using a 240 bp Nco I- Pvu II fragment of LH12 (Fig. 7) as a 32 P labeled hybridization probe. The clone LH6 (Fig. 7) is isolated from this screening. LH6 contains the complete 3' end of beta LH, including the region corresponding to the untranslated portion of the mRNA through 27 A residues of the poly A "tail" of the mRNA. No clones are found that extended further than LH12 in the 5' direction. DNA sequencing of the complete, combined mature beta LH coding regions reveals two differences in the amino acid sequence of beta LH from the published protein sequence data: position 42 is a methionine and position 55 is a valine. Also, the mature beta LH contains 121 amino acids, based on the cDNA sequence. A clone containing an intact signal peptide coding sequence and the complete mature beta LH sequence is constructed as shown in Fig. 8, using the restriction fragment illustrated in Fig. 7. A 104 bp Eco RI- Dde I fragment is isolated from the plasmid beta 579 H and ligated to an isolated 181 bp Dde I fragment, subsequently digested with Pst I, from the LH12 plasmid. Following ligation overnight at 15°C, the ligation mix is digested with Eco RI and Pst I and fractionated on a 7% polyacrylamide gel from which the desired 256 bp fragment is isolated. This fragment fuses the beta hCG signal sequence to that of the pre-beta LH in such a way as to provide a coding sequence for a 20 amino acid signal peptide. The 256 bp Eco RI- Pst I fragment is cloned into pBR 322 digested with Eco RI and Pst I so as to give the plasmid LH beta 260. The 146 bp Eco RI- Nco I fragment indicated in Fig. 8 is isolated from a polyacrylamide gel and used later in the construction as described below. The LH6 plasmid (Fig. 8) is digested with Sau 3a and the 390 bp fragment is isolated by polyacrylamide gel electrophoresis. This fragment is then digested with Hinc II, ligated to Bam HI linkers, digested with Bam HI, and cloned into the plasmid pAPP at the Bam HI site. pAPP is derived from pBR 322 by digestion with Ava I, filling in the 5' overhang with the dNTP's and the large fragment DNA polymerase I of E. coli , digestion with Pvu II, and ligation to close the plasmid so as to eliminate the Pvu II site. The plasmid LH6B, isolated from the ligation of the 340 bp Bam HI fragment into the Bam HI site of pAPP, is digested with Eco RI and Pvu II, and treated with bacterial alkaline phosphatase. The fragments are ligated to a mixture of the 145 bp Eco RI- Nco I fragment of LH beta 260, described above, and the isolated 241 bp Nco I- Pvu II fragment from the plasmid LH12 shown in Fig. 8. The ligation mix is used to transform E. coli to ampicillin resistance. The plasmid LH 520 H/B is found among the transformants. LH 520 H/B contains a complete beta LH coding sequence including a hybrid signal peptide sequence. Construction of p Alpha LHSVVP1 In order to express this pre-beta LH clone in an SV40-based vector, as had been done for the pre-alpha and pre-beta hCG clones described previously, it is desirable to place an Eco RI site very close to the ATG of the pre-beta coding sequence. This is accomplished by digesting LH520 H/B with Hga I, filling in the 5' overhang, ligating on synthetic Eco RI linkers, digesting with Eco RI and Bam HI, and cloning the isolated 496 bp Eco RI- Bam HI fragment into pBR 322 digested with Eco RI and Bam HI and treated with bacterial alkaline phosphatase. The plasmid pLH496 R/B is isolated from E. coli transformed with this ligation mix and is used as the source of the 496 bp fragment to be expressed. The plasmid p alpha beta VP1, whose construction and use in expressing both subunits of hCG is described earlier (Fig. 3), is digested with Eco RI and Bam HI and ligated in a reaction mix containing the plasmid pLH496 R/B which had been digested with both of these enzymes (Fig. 9). The plasmid p alpha LHVP1 is identified among the E. coli transformants. As shown in Fig. 9, the intact SV40 viral early region is taken from p alpha SVHVP1 (Fig. 1) and inserted by ligation as a Kpn I- Sal I fragment into p alpha LHVP1 which had been digested with Kpn I and Sal I to give the plasmid p alpha LHSVVP1. By cutting this plasmid with Bam HI and religating, the virus alpha LHSVVP1 is formed. This virus contains cloned cDNA's for the common (to LH and hCG, as well as FSH and TSH) alpha subunit and the specific beta LH subunit under control of the SV40 late promoter. The cloned cDNA's are positioned in such a way that the common alpha insert replaced the viral VP1 protein coding sequence and the beta LH insert replaced the viral VP2 coding sequence. Insertion of the Beta LH cDNA (With Beta hCG 5' End of Signal Peptide) into a BPV-Based Expression System LH 520 H/B (Fig. 8) is digested with Hind III and Bam HI, treated with the E. coli DNA polymerase (Klenow), ligated to synthetic Sal I linkers, digested with Sal I, and cloned into the Sal I site of pBR 322. The resulting plasmid, LH 530 Sal, is used as a source of the LH cDNA clone for insertion into the mouse metallothionein gene of the plasmid CL28 as described in Fig. 10. CL28 is cut with Bgl II, treated with nuclease Sl, and ligated to Xho I linkers. Following digestion with Xho I, ligation and digestion with Bgl II, E. coli is transformed with the reaction mix to give the plasmid CL28Xho. This plasmid is digested with Bam HI and Sal I and ligated to a Bam HI plus Sal I digest of the plasmid pB2-2 (Fig. 4) to give the plasmid CL28 Xho BPV. The latter LH insert is then ligated into the Xho I site of CL28 Xho BPV as a Sal I fragment, since the 5' overhang of Sal I digests is complementary to that of Xho I digests. Following digestion with Xho I to eliminate background, E. coli is transformed and the desired plasmid pCL28XhoLHBVP containing the (hybrid) pre-beta LH insert, in a BPV-based plasmid, under control of the mouse metallothionein promoter, is isolated. Transfection and Infection of Host Monkey Cells The incorporation of virus-containing vectors into eukaryotic cells for the production of a heteropolymeric protein is generally accomplished as follows. First, if the viral DNA and homopolymeric protein-encoding DNA are incorporated into a plasmid, which is maintained, in, say, E. coli , the plasmid sequences (e.g. the pBR 322 sequences) are removed and the resulting DNA is ligated to form circular DNA including the viral region and the heteropolymeric protein-encoding sequence or sequences. This circular DNA generally does not contain all of the genetic information needed to produce a replicating virus, the other necessary sequences (e.g. those encoding coat protein) having been replaced by the heteropolymeric protein-encoding sequence or sequences. The circular DNA, minus the plasmid DNA, must be close enough in size to the naturally occurring viral DNA from which it is derived to permit the DNA to enter and replicate in appropriate host mammalian cells. The circular DNA is used to transfect host cells in order to produce virus stock for later infections. Since some of the DNA necessary to produce virus is missing, the transfection must occur in conjunction with helper virus DNA encoding enough of the missing function to produce replicating virus. Transfected host cells are grown and incubated until lysed by replicating virus. The resulting replicating virus stock, including helper virus, is then used to infect host cells for production of the heteropolymeric protein. Virus stock is maintained, since it generally needs to be reused to infect fresh batches of host cells, as each culture of infected, protein-producing host cells generally is eventually lysed by the virus. The specific recombinant DNA sequences described above are used to transfect, and then infect, host cells, as follows. The pBR 322 sequences are removed from the above-described SV40-containing plasmids to produce transfecting viral DNA. In the case of p alpha SVHVP1 and p alpha beta SVVPI, this is accomplished by digestion with Bam HI, followed by ligation under conditions favoring circularization of the fragments to give (among other products) alpha SVHVP1 and alpha beta SVVPI. For p beta SVVP1, digestion with Eco RI followed by re-ligation brings the SV40 late promoter and VP1 splice region into juxtaposition with the beta hCG cDNA insert at the same time that it eliminates pBR 322 sequences and forms beta SVP1. At the same time, ptsA58 Bam (tsA58 SV40 viral DNA cloned into the pBR 322 Bam HI site) is cut with Bam HI and ligated to obtain self-ligated circles. Analogous methods are used for the LH vectors. Separate virus stocks are prepared as described below. The DNA's, which are cut and ligated as described above, are ethanol precipitated and dissolved in sterile water. Approximately 1 ug of ptsA58 Bam DNA (helper virus) and 10 ug of recombinant DNA (encoding alpha and/or beta hCG or LH) are combined in a sterile test tube, mixed with 2 ml of TBS buffer (G. Kimura and R. Dulbecco 1972, Virogy, 49 , 79-81) and 1 ml of 2 mg/ml DEAE-dextran solution and added to a monolayer of confluent monkey CV-1 cells previously washed twice with 10 ml of TBS in a T-75 flask. The cells are left at 37°C for 1-2 hrs with occasional shaking, washed with TBS twice, fed with 10 ml of DMEM containing 5% fetal calf serum, and left at 40°C for 10-15 days. After complete cell lysis, the medium is transferred to a test tube, frozen and thawed five times, and centrifuged at 3000 rpm for five minutes. The resulting supernatants serve as virus stocks for infection of fresh CV-1 cells. To accomplish an infection, CV-1 cells are grown to confluence in a T-150 flask. 1 ml of one of the virus stocks (made as described above) is added to the flask and the cells are incubated at 40 o C for 5 days. For mixed infections, CV-1 cells are grown to confluence in a T-150 flask. alpha SVHVP1 and beta SVP1 viruses are mixed in a 1:1 ratio and 1 ml of the mixed virus is used to infect CV-1 cells at 40 o C. Transfection of Mouse Cells To produce heterodimeric hCG using a mixed transfection, five ug of each BPV plasmid, i.e., pRF 375 (alpha hCG) and pRF 398 (beta hCG), are mixed and added to 0.5 ml of a 250 mM CaCl 2 solution containing 10 ug of salmon sperm DNA as carrier. This mixture is bubbled into 0.5 ml of 280 mM NaCl, 50 mM Hepes and 1.5 mM sodium phosphate. The calcium phosphate precipitate is allowed to form for 30-40 minutes at room temperature. 24 hours prior to transfection, 5x10 5 cells of mouse C127 cells (available from Dr. Dean Hamer, National Cancer Institute, NIH, Bethesda, MD) are placed in a 100 mm dish or T-75 flask. Immediately before adding the exogenous DNA, the cells are fed with fresh medium (Dulbecco's Modified Medium, 10% fetal calf serum). One ml of calcium phosphate precipitate is added to each dish (10 ml), and the cells are incubated for 6-8 hours at 37 o C. The medium is aspirated and replaced with 5 ml of 20% glycerol in phosphate buffered saline, pH 7.0 (PBS) for 2 minutes at room temperature. The cells are washed with PBS, fed with 10ml of medium, and incubated at 37 o C. After 20-24 hours, the medium is changed and subsequent refeeding of the cells is carried out every 3-4 days. Individual clones are grown in T-25cm flasks. After 7-21 days, cell clones can be transferred to larger flasks for analysis. To produce heterodimeric hCG using a single transfection, plasmid RF 398 alpha t 2 is employed in the same manner as the above two plasmids were employed for a mixed infection. To make heterodimeric LH, plasmids PRF 375 and pCL28XhoLHBPV are mixed, as described above in the case of hCG. An interesting observation is that culturing cells containing beta hCG or beta LH-encoding vectors alone, in the absence of alpha-encoding cells, produces practically no beta subunit, while cells containing alpha and beta-encoding sequences produce not only heterodimer, but free beta subunit as well. This lends support to the notion that the production of both subunits in a single cell culture has the additional advantage of somehow permitting the presence of the alpha subunit to stabilize the beta subunit. Deposits The following, described above, have been deposited in the American Type Culture Collection, Rockville, MD: alpha beta SVVP1, ATTC VR2077 ; alpha SVHVP1, ATCC VR2075 ; beta SVVP1, ATCC VR2075 ; pRF 375 in C127 cells, ATCC CRL8401 ; pRF 398 in C127 cells, ATCC CRL8401 ; pCL28XhoLHBPV E. coli, ATCC 39475 ; pRF 398 alpha t 2 in C127 cells. Use Transfected cells of the invention can be used to produce biologically active luteinising hormone. Other Embodiments Other embodiments are within the following claims. For example: Other host cells, vectors, promoters, transforming sequences, and viruses can also be employed. The host cell employed generally is dependent on the vector being used. For example, when the vector is replicating virus or non-replicating viral DNA, the host cells are cells capable of being infected or transfected, respectively, by those vectors; e.g., SV40-containing vectors require monkey host cells, preferably CV-1 cells. Where the cloning vector is a plasmid having procaryotic control sequences, prokaryotic host cells, e.g., E. coli, are used. Where the cloning vector is a plasmid having eukaryotic control sequences, appropriate eukaryotic host cells, e.g., mouse C127 cells, are used.

Claims: A DNA molecule comprising a DNA sequence encoding a luteinising hormone (LH) having an α and β subunit, the β subunit having the residues Met 42 and Val 55 . An expression vector capable of transfecting a eukaryotic cell, the vector comprising heterologous DNA encoding the α and β subunits of biologically active, post-translationally modified luteinising hormone (LH), the β subunit being 121 amino acids in length and having the residues Met 42 and Val 55 . A vector as claimed in claim 2 which was used to transfect E. coli deposited under ATCC 39475. A vector as claimed in claim 2 or 3 wherein the heterologous DNA encoding each subunit is under the control of a respective promoter. A vector as claimed in any of claims 2 to 4 comprising the SV40 late promoter, the bovine papilloma virus promoter or the mouse metallothionein promoter. A vector as claimed in any of claims 2 to 4 which comprises plasmid-derived DNA and/or replicating virus-derived DNA, such as at least the 69% transforming region of the bovine papilloma virus genome. A set of expression vectors, each vector being capable of transfecting a eukaryotic cell, each vector comprising heterologous DNA encoding a respective α and β subunit of biologically active, post-translationally modified luteinising hormone (LH), the β subunit being 121 amino acids in length and having the residues Met 42 and Val 55 , wherein the α and β subunits of the LH are encoded by heterologous DNA in the vectors. A set of vectors as claimed in claim 7 wherein each expression vector comprises the SV40 late promoter, the bovine papilloma virus promoter or the mouse metallothionein promoter. A set of vectors as claimed in claim 7 wherein each expression vector comprises plasmid-derived DNA and/or replicating virus-derived DNA. A eukaryotic cell transfected with one or more expression vectors, the cell being capable of producing biologically active post-translationally modified luteinising hormone (LH) having α and β subunits, the β subunit of LH being 121 amino acids in length and having the residues Met 42 and Val 55 , the subunits of the LH being encoded by heterologous DNA in the expression vector(s). A cell as claimed in claim 10 which is transfected with more than one expression vector, each vector comprising heterologous DNA encoding a respective subunit. A cell as claimed in claim 10 which is transfected with a single expression vector comprising heterologous DNA encoding each subunit. A cell as claimed in any of claims 10 to 12 wherein the heterologous DNA encoding each subunit is under the control of a respective promoter. A cell as claimed in any of claims 10 to 13 wherein the heterologous DNA encoding at least one subunit is under the control of the SV40 late promoter, the mouse metallothionein promoter or the bovine papilloma virus promoter. A cell as claimed in any of claims 10 to 14 wherein the or each expression vector comprises plasmid-derived DNA and/or replicating virus-derived DNA, for example wherein the or each vector comprises at least 69% transforming region of the bovine papilloma virus genome. A process for the preparation of a protein which is biologically active, post-translationally modified luteinising hormone (LH) having an α and β subunit, the β subunit being 121 amino acids in length and having the residues Met 42 and Val 55 the process comprising commonly synthesising the α and β subunit of LH in a eukaryotic cell transfected with one or more expression vectors comprising heterologous DNA encoding each of the subunits. A process according to claim 6 wherein the post-translational modification is glycosylation. A process as claimed in claim 16 or 17 wherein the cell is transfected with more than one expression vector, each vector comprising heterologous DNA encoding a respective subunit. A process as claimed in claim 17 or 18 wherein the cell is transfected with a single expression vector comprising heterologous DNA encoding each subunit. A process as claimed in any of claims 16 to 19 wherein the heterologous DNA encoding each subunit is under the control of a respective promoter. A process as claimed in any of claims 16 to 20 wherein the heterologous DNA encoding at least one subunit is under the control of the SV40 late promoter or the bovine papilloma virus promoter. A process as claimed in any of claims 16 to 21 wherein the heterologous DNA encoding at least one subunit is under the control of the mouse metallothionein promoter. A process as claimed in any of claims 16 to 22 wherein the or each expression vector comprises plasmid-derived DNA and/or replicating virus-derived DNA. A process as claimed in claim 23 where the or each vector comprises at least the 69% transforming region of the bovine papilloma virus genome. A protein which is biologically active, post-translationally modified, luteinising hormone (LH) having an α and β subunit, the β subunit being 121 amino acids in length and having the residues Met 42 and Val 55 . A protein according to claim 25 which is a recombinant protein. A protein according to claim 25 or 26 for use in medicine. A pharmaceutical composition comprising a protein as defined in claim 25 or 26 and a carrier. A process for the preparation of a vector according to any of claims 2 to 6, the process comprising DNA ligation and/or synthesis. A process for preparing a set of expression vectors according to any of claims 7 to 9, the process comprising preparing each vector by DNA ligation and/or synthesis. A process for the preparation of a transfected eukaryotic cell according to any of claims 10 to 15, the process comprising transfecting a eukaryotic cell with one or more expression vectors as described in any of claims 2 to 9. A process for preparing a pharmaceutical composition according to claim 28, the process comprising admixing a carrier with a protein as claimed in any of claims 25 to 27.

Inventors: BECK ANTON K, BERNSTINE EDWARD G, HSING NANCY, REDDY VEMURI B, BECK, ANTON K., BERNSTINE, EDWARD G., HSING, NANCY, REDDY, VEMURI B.
Applicants: APPLIED RESEARCH SYSTEMS, APPLIED RESEARCH SYSTEMS ARS HOLDING N.V.
Application year: 1984
Main classification: C12N15
IPC codes: C12N15, A61K38