Androgen-regulated expression of a cloned rat prostatic c3 gene transfected into mouse mammary tumor cells

5alpha-Androstane-3alpha,17beta-diol activates pathway that resembles the epidermal growth factor responsive pathways in stimulating human prostate cancer LNCaP cell proliferation

5alpha-Androstane-3alpha,17beta-diol (3alpha-diol) is considered to have no androgenic effects in androgen target organs unless it is oxidized to 5alpha-dihydrotestosterone (5alpha-DHT). We used microarray and bioinformatics to identify and compare 3alpha-diol and 5alpha-DHT responsive gene in human prostate LNCaP cells. Through a procedure called 'hypervariable determination', a similar set of 30 responsive genes involving signal transduction, transcription regulation, and cell proliferation were selected in 5alpha-DHT-, 3alpha-diol-, and epidermal growth factor (EGF)-treated samples. F-means cluster and networking procedures showed that the responsive pattern of these genes was more closely related between 3alpha-diol and EGF than between 5alpha-DHT and 3alpha-diol treatments. We conclude that 3alpha-diol is capable of stimulating prostate cell proliferation by eliciting EGF-like pathway in conjunction with androgen receptor pathway.

In utero exposure to antiandrogens alters the responsiveness of the prostate to p,p'-DDE in adult rats and may induce prostatic inflammation

DDE is an environmental pollutant with antiandrogenic properties. Following administration to pregnant rats, DDE was shown to cause feminization in the male offspring at the neonatal stages but did not affect the pubertal growth of accessory sex organs. In this study, we examined the potential of in utero exposure to antiandrogens to alter the responsiveness of the male rats to subsequent DDE challenge. Pregnant Long-Evans rats were dosed by gavage from Gestation Day 14 to 18 at 0, 10 (low dose), or 100 (high dose) mg DDE, or 40 mg flutamide/kg body wt (bw)/day (in utero treatment). At approximately 80 days of age, the male offspring from each of the four in utero treatment groups were divided into two groups. One group received the adult treatment of four daily gavage administrations of DDE at 70 mg/kg bw (adult treatment), while the second group served as the adult treatment control (adult control). The in utero treatment resulted in 18, 31, and 53% reductions of ventral prostate weights at approximately 85 days of age compared to the control for the low- and high-dose DDE and flutamide groups, respectively. These results suggest that the in utero antiandrogen treatments produced a latent effect on prostate growth that became pronounced only in the postpubertal stage. The in utero treatment also altered the responsiveness of the prostate to the adult treatment, indicated by a significant reduction in ventral prostate weight that was seen only in the control group of the in utero treatment but not in the other groups. The in utero treatment was also associated with expression of testosterone-repressed prostatic message-2 in the adult ventral prostate. In addition, a few prostates in the high-dose DDE- and flutamide-treated groups of the in utero treatment were found to have chronic suppurative prostatitis. While other types of hormonal manipulations have been shown to incite similar responses in rat prostate, the possible linkage between in utero antiandrogen treatment and prostatic inflammation needs to be further evaluated.

Purification of estramustine-binding protein and production of monoclonal antibodies to its different components

Estramustine-binding protein (EMBP) is a heterodimeric 46-kDa glycoprotein that is secreted from the prostate. Upon reductive cleavage it decomposes into two closely related components, C1 and C2, and the shared glycosylated peptide C3. EMBP binds estramustine and estromustine, the active metabolites of estramustine phosphate (Estracyt), which is a drug with antimitotic properties used in the treatment of prostatic carcinoma. In the present study, a two-step procedure (i.e., anion-exchange and Con A-Sepharose chromatography) is described for the isolation of EMBP in high yield from rat prostate tissue. Mouse monoclonal antibodies (mAbs) were produced using the major DEAE-Sepharose fraction of EMBP as an immunogen. Eleven mAbs were selected by screening in a solid-phase ELISA. One displayed high-affinity binding with soluble EMBP (Ka approximately 3 x 10(10) M-1) and crossreacted with a human prostate tumor extract in a radioimmunoassay. The epitopes defined by these mAbs were analyzed by Western immunoblotting. All constituents of EMBP, except component C1, were identified by at least one antibody. Nine visualized either one or both of the two EMBP subunits under denaturing conditions, two of which retained their reactivity after reduction of disulfide bridges. One epitope was exposed to its mAb only when the antigen was in its reduced state. The immunoreactivity was eliminated by protease treatment, whereas deglycosylation with glycopeptidase F had a minimal effect. EMBP has been detected in tissues other than the prostate as well as in prostate neoplastic specimens and in several other human malignancies. Hence, these mAbs will be a useful tool in the characterization of EMBP in different tissues and in evaluating existing and in defining new indications for Estracyt therapy.

Sequence analysis and characterization of FAR-17c, an androgen-dependent gene in the flank organs of hamsters

This study reports on the isolation and characterization of a cDNA clone, regulated by androgen transcriptionally, in male Golden hamsters' flank organs. Previous studies have reported on the cloning of an androgen-dependent gene, FAR-17a, from the same hamster organ. After castration, the FAR-17c transcription rate decreases faster than FAR-17a but is not suppressed completely. The recovery of transcription by androgen injection is also faster than FAR-17a. In male hamsters, it is expressed strongly in the sebaceous glands and liver, and weakly in the lungs and brain. It has never been expressed in the testes. In the female, it is strongly expressed in the liver and brain and weakly in the lungs and flank organs. Sequence analysis shows that FAR-17c has a long 1062 bp open reading frame and its deduced amino acid sequence (354 residues) is highly homologous to the stearyl-CoA desaturases of the rat liver and mouse adipocytes. Stearyl-CoA desaturase, either in the liver or adipocytes appears to be independent of androgen regulation. Since stearyl-CoA desaturase plays a key role in fatty acid metabolism, further studies on its regulation by androgen are warranted in relation to acne vulgaris.

Steroid-induced epithelial-fibroblastic conversion associated with syndecan suppression in S115 mouse mammary tumor cells

Cell-matrix interactions play an important role in the maintenance of cell shape, supposed to be mediated by the anchorage of cellular cytoskeleton to extracellular matrix via matrix receptors. In this work the expression of one of the known matrix receptors, syndecan, was studied during the hormone-induced change in the phenotype of Shionogi 115 (S115) mouse mammary tumor cells. In the presence of testosterone, when S115 cells express fibroblastic phenotype, they increased their growth rate and became gradually anchorage independent. These cells, however, revealed strong RGDS-dependent binding to fibronectin (FN) but not binding to the heparin-binding domain of FN. Instead, S115 cells growth without testosterone showed epithelial morphology and binding to the heparin-binding domain of FN, suggesting an alteration of syndecan expression in hormone-treated S115 cells. As quantitated by radioimmunoassay and by Western blot, the amounts of both matrix-binding ectodomain of syndecan and syndecan mRNA (2.6 kb) declined in hormone-treated S115 cells. The addition of antiandrogen cyproterone acetate to culture medium opposed the effect of testosterone on syndecan mRNA. We thus propose that the inactivation of syndecan gene and the consequent suppression of syndecan expression is related to the altered adhesion properties, the disappearance of epithelial phenotype, and, on the other hand, to the appearance of transformed-like phenotype in hormone-treated S115 cells.

Tissue-specific and hormonal regulation of the gene for rat prostatic steroid-binding protein in transgenic mice

We investigated the tissue-specific and hormonal regulation of the gene for rat prostatic steroid-binding protein by introducing the C3(1) gene with 4-kilobase (kb) upstream and 2-kb downstream flanking sequences into transgenic mice. There was selective expression in the ventral prostate that was stimulated by testosterone, which indicated that the gene together with 6-kb flanking DNA contains the information required for prostate-specific and testosterone-regulated expression.

Transcriptional and posttranscriptional mechanisms regulate murine thymidine kinase gene expression in serum-stimulated cells

We previously isolated and characterized the structure of murine thymidine kinase (tk) genomic and cDNA sequences to begin a study designed to identify regions of the tk gene important for regulated expression during the transition of cells from G0 to a proliferating state. In this report, we describe the stable transfection of the cloned gene into L-M(TK-) cells and show that both thymidine kinase (TK) enzyme activity and DNA synthesis increase in parallel when transfectants in G0 arrest are stimulated by serum. To define promoter and regulatory regions more precisely, we have constructed a series of tk minigenes and have examined their expression in stable transfectants after serum stimulation. We have identified a 291-base-pair DNA fragment at the 5' end of the tk gene that has promoter function, and we have determined its sequence. In addition, we have found that DNA sequences which mediate serum-induced expression of TK are transcribed, since expression of the murine tk cDNA, fused to a promoter from either the murine tk gene, the simian virus 40 early region, or the herpes simplex virus tk gene, is stimulated by serum. Our constructs also reveal that the murine tk polyadenylation signal is not required for regulation, nor is most of the 3' untranslated region. RNA dot blot analysis indicates that murine cytoplasmic tk mRNA levels always parallel TK enzyme activity. Nuclear runon transcription assays show less than a 2-fold increase in transcription from the cloned tk gene in serum-stimulated transfectants, but an 11-fold increase in mouse L929 cells, which are inherently TK+. These results taken together suggest that the murine tk gene is controlled in serum-stimulated cells by a transcriptional mechanism influenced by DNA sequences that flank tk and also by a posttranscriptional system linked to gene sequences that are transcribed.

Molecular genetics of androgen-inducible RP2 gene transcription in the mouse kidney

Androgen control of the RP2 gene in the mouse kidney has been modified during evolution. In inbred mice (Mus domesticus), the concentrations of mRNAs encoded by RP2 undergo a 10- to 12-fold induction in response to testosterone; in other Mus species (e.g., Mus hortulanus and Mus caroli), induction ranges from none to about two- to fourfold. In this communication, we show that androgens induced RP2 transcription in M. domesticus, although this induction may not have fully accounted for the increase in mRNA levels. Reduced mRNA inducibility in M. hortulanus and in several other species was associated with an absence of transcriptional induction. Analysis of an interspecies backcross population indicated that the difference in RP2 inducibility between M. domesticus and M. hortulanus was due to a single Mendelian locus tightly linked (0 of 47 recombinants) to RP2. The RP2 gene was found to contain at least two promoters, only one of which was highly sensitive to testosterone. These results indicate that induction of the RP2 mRNAs, as well as interspecies variations in RP2 inducibility, are primarily a consequence of effects on this promoter.

Tissue-specific and hormonal regulation of the gene for rat prostatic steroid-binding protein in transgenic mice

We investigated the tissue-specific and hormonal regulation of the gene for rat prostatic steroid-binding protein by introducing the C3(1) gene with 4-kilobase (kb) upstream and 2-kb downstream flanking sequences into transgenic mice. There was selective expression in the ventral prostate that was stimulated by testosterone, which indicated that the gene together with 6-kb flanking DNA contains the information required for prostate-specific and testosterone-regulated expression.

Molecular genetics of androgen-inducible RP2 gene transcription in the mouse kidney

Androgen control of the RP2 gene in the mouse kidney has been modified during evolution. In inbred mice (Mus domesticus), the concentrations of mRNAs encoded by RP2 undergo a 10- to 12-fold induction in response to testosterone; in other Mus species (e.g., Mus hortulanus and Mus caroli), induction ranges from none to about two- to fourfold. In this communication, we show that androgens induced RP2 transcription in M. domesticus, although this induction may not have fully accounted for the increase in mRNA levels. Reduced mRNA inducibility in M. hortulanus and in several other species was associated with an absence of transcriptional induction. Analysis of an interspecies backcross population indicated that the difference in RP2 inducibility between M. domesticus and M. hortulanus was due to a single Mendelian locus tightly linked (0 of 47 recombinants) to RP2. The RP2 gene was found to contain at least two promoters, only one of which was highly sensitive to testosterone. These results indicate that induction of the RP2 mRNAs, as well as interspecies variations in RP2 inducibility, are primarily a consequence of effects on this promoter.

The structure and function of steroid receptor proteins

This review has highlighted several topics in the study of steroid hormone action. The unanswered questions regarding the mechanism of ligand-controlled LRF activity, the extent of evolutionary conservation and specificity of DNA binding, and the validity of various models of transcriptional regulation mediated through gene networks point to the future direction of research in this field. Steroid hormones are used extensively in clinical treatments, especially glucocorticoids. Our laboratory is attempting to determine which gene networks are responsible for some of these clinical phenotypes. Figure 5 points out that the study of glucocorticoid action holds a unique position because it spans both the basic sciences and the field of applied molecular biology. Now that we have a fundamental knowledge of the necessary elements required for steroid-dependent regulation of gene expression, we can better investigate the clinical responses to steroid therapy (which include devastating side effects) by isolating and characterizing the important target gene(s). In this author's opinion, future directions in the study of steroid responsiveness will have to include a systematic approach toward deciphering a variety of these LRF-regulated gene networks in experimentally feasible systems. Hopefully, work in this area may be revealing and perhaps beneficial to ongoing clinical studies. In addition, the study of mechanisms of transcriptional induction and repression, using the model system of LRFs, could be applicable to many gene regulatory systems which are controlled by such processes as development and differentiation.

Transcriptional and posttranscriptional mechanisms regulate murine thymidine kinase gene expression in serum-stimulated cells

We previously isolated and characterized the structure of murine thymidine kinase (tk) genomic and cDNA sequences to begin a study designed to identify regions of the tk gene important for regulated expression during the transition of cells from G0 to a proliferating state. In this report, we describe the stable transfection of the cloned gene into L-M(TK-) cells and show that both thymidine kinase (TK) enzyme activity and DNA synthesis increase in parallel when transfectants in G0 arrest are stimulated by serum. To define promoter and regulatory regions more precisely, we have constructed a series of tk minigenes and have examined their expression in stable transfectants after serum stimulation. We have identified a 291-base-pair DNA fragment at the 5' end of the tk gene that has promoter function, and we have determined its sequence. In addition, we have found that DNA sequences which mediate serum-induced expression of TK are transcribed, since expression of the murine tk cDNA, fused to a promoter from either the murine tk gene, the simian virus 40 early region, or the herpes simplex virus tk gene, is stimulated by serum. Our constructs also reveal that the murine tk polyadenylation signal is not required for regulation, nor is most of the 3' untranslated region. RNA dot blot analysis indicates that murine cytoplasmic tk mRNA levels always parallel TK enzyme activity. Nuclear runon transcription assays show less than a 2-fold increase in transcription from the cloned tk gene in serum-stimulated transfectants, but an 11-fold increase in mouse L929 cells, which are inherently TK+. These results taken together suggest that the murine tk gene is controlled in serum-stimulated cells by a transcriptional mechanism influenced by DNA sequences that flank tk and also by a posttranscriptional system linked to gene sequences that are transcribed.

A complex androgen-responsive enhancer resides 2 kilobases upstream of the mouse Slp gene

Neighboring genes encoding the mouse sex-limited protein (Slp) and fourth component of complement (C4) show extensive homology. In contrast to C4, however, Slp is regulated by androgen. One region of the Slp gene capable of hormonal response following transfection was located about 2 kilobases upstream of the transcription start site, where the C4 and Slp sequences diverge. This region, delimited here to a 0.75-kilobase fragment, showed cryptic promoter activity as well as androgen responsiveness in either orientation in front of the bacterial chloramphenicol acetyltransferase coding region. When this fragment was placed upstream of a viral long terminal repeat, increased chloramphenicol acetyltransferase expression derived from the viral promoter. Proteins from nuclear extracts specifically bound to four sequences within the region, near sites that are DNase I hypersensitive in vivo and reflect the hormonal and developmental regulation of Slp. Like several other cellular enhancers, this androgen-responsive element seems to be modular in nature and complex in its function.

A complex androgen-responsive enhancer resides 2 kilobases upstream of the mouse Slp gene

Neighboring genes encoding the mouse sex-limited protein (Slp) and fourth component of complement (C4) show extensive homology. In contrast to C4, however, Slp is regulated by androgen. One region of the Slp gene capable of hormonal response following transfection was located about 2 kilobases upstream of the transcription start site, where the C4 and Slp sequences diverge. This region, delimited here to a 0.75-kilobase fragment, showed cryptic promoter activity as well as androgen responsiveness in either orientation in front of the bacterial chloramphenicol acetyltransferase coding region. When this fragment was placed upstream of a viral long terminal repeat, increased chloramphenicol acetyltransferase expression derived from the viral promoter. Proteins from nuclear extracts specifically bound to four sequences within the region, near sites that are DNase I hypersensitive in vivo and reflect the hormonal and developmental regulation of Slp. Like several other cellular enhancers, this androgen-responsive element seems to be modular in nature and complex in its function.

Androgen-regulated expression of secretory protein synthesis in mouse ventral prostate

Two proteins of molecular weights 25 and 12 kDa (p25 and p12 respectively), whose expression is regulated by testosterone, were identified in mouse ventral prostate. An antiserum raised to mouse ventral prostate secretion was used to demonstrate that p25 corresponds to the major secretory glycoprotein in mouse prostatic fluid. This antiserum does not cross-react with the major secretory proteins of the rat ventral prostate. Western blot analysis of mouse ventral prostate proteins using the prostatic secretion antiserum demonstrates that p12 and p25 are detectable at 3 weeks of age, but the maximum level of both proteins is not attained until 5 weeks of age. In addition, synthesis of p25 was also observed in prostate tissue derived from differentiated embryonic urogenital sinus tissue growing as implants under the renal capsule of syngeneic male hosts.

Transcriptional control of the mouse alpha 2(I) collagen gene: functional deletion analysis of the promoter and evidence for cell-specific expression

A chimeric gene was constructed in which sequences between 2,000 base pairs upstream of the start of transcription of the mouse alpha 2(I) collagen gene and 54 base pairs downstream of this site were fused to the chloramphenicol acetyltransferase (CAT) gene. We present evidence suggesting that this collagen gene segment is sufficient for cell-specific expression of the chimeric gene. Indeed, the levels of CAT activity in transient expression experiments were at least 10 times higher after transfection of NIH 3T3 cells than after transfection of a mouse myeloma cell line, whereas much less difference was found after transfection of these two cell types with pSV2-CAT, a plasmid in which the early simian virus 40 promoter is fused to the CAT gene. Several deletions were introduced in the same 5'-flanking segment of the alpha 2(I) collagen gene, and the effects of these deletions were examined after DNA transfection of the chimeric collagen-CAT gene into NIH 3T3 cells. At least two segments broadly located between -979 and -502 and between -346 and -104 are needed for optimal expression of the chimeric gene. These results were obtained both in transient expression experiments and by analysis of pools of NIH 3T3 cells that were stably transfected with the different mutants. In general, the effects of the deletions on the activity of the alpha 2(I) collagen promoter were analogous, whether the plasmids harbored the simian virus 40 enhancer sequence or not, although the overall levels of expression of the chimeric gene were increased when the recombinant plasmids contained this sequence.

Androgen regulation by the long terminal repeat of mouse mammary tumor virus

Mouse mammary tumor virus (MMTV) has long been implicated in mouse mammary carcinogenesis, and it is now well established that the long terminal repeat (LTR) contains regulatory sequences responsible for glucocorticoid-mediated induction of viral RNA. However, we have demonstrated previously that androgens as well as glucocorticoids can regulate MMTV RNA in the S115 mouse mammary tumor cell line. To determine if androgens act directly on the LTR in these cells, plasmids were constructed with the MMTV LTR joined to the coding sequences of genes not normally expressed in the cells. Following transfection of these chimeric genes into S115 cells, we show that the expression of the genes is regulated by both androgens and glucocorticoids. Furthermore, hormonal regulation is also conferred by the LTR on the neighboring guanine phosphoribosyltransferase (gpt) gene. Thus, androgens can act on the LTR of MMTV when the appropriate receptors are present in the cells, and this interaction can influence the expression of additional adjacent genes.

Characterization of androgen receptors in a transplantable human prostatic adenocarcinoma (PC-82)

The transplantable human prostatic adenocarcinoma, PC-82, has been shown to be a suitable model for the study of several aspects of androgen-regulated tumor growth. This tumor contains an androgen receptor, and the purpose of the present investigation was to characterize this androgen receptor with respect to hormone specificity, sedimentation coefficient, dissociation constant, Stokes radius, ionic properties, and molecular mass. Cytosol was prepared from tumor tissues grown in athymic nude mice, which were castrated 10 days before harvesting the tumor. Scatchard plot analysis revealed a binding protein with a Kd of 0.1 nM for R1881 (methyltrienolone) and binding capacity of 120 fmol/mg protein. The receptor showed a high affinity for R1881, testosterone, and 5 alpha-dihydrotestosterone, respectively, whereas no or little affinity was found for progesterone and estradiol. In the presence of 10 mM molybdate the androgen receptor in PC-82 cytosol eluted from an FPLC anion exchange column (Mono Q) at 0.32 M NaCl, which is identical to what has been found for androgen receptors from rat prostate and calf uterine cytosol. Photoaffinity labeling of the [3H]R1881-androgen receptor complex and subsequent analysis on SDS-polyacrylamide gels resulted in a covalently labeled protein with a molecular mass of approximately 50 kD. The androgen receptor of the PC-82 tumor had a sedimentation coefficient of 4S and a Stokes radius of 3.3 nm at high ionic strength (0.4 M NaCl). It is concluded that the PC-82 tumor contains a binding protein with the properties described for androgen receptors present in prostate tissue.

Androgen regulation by the long terminal repeat of mouse mammary tumor virus

Mouse mammary tumor virus (MMTV) has long been implicated in mouse mammary carcinogenesis, and it is now well established that the long terminal repeat (LTR) contains regulatory sequences responsible for glucocorticoid-mediated induction of viral RNA. However, we have demonstrated previously that androgens as well as glucocorticoids can regulate MMTV RNA in the S115 mouse mammary tumor cell line. To determine if androgens act directly on the LTR in these cells, plasmids were constructed with the MMTV LTR joined to the coding sequences of genes not normally expressed in the cells. Following transfection of these chimeric genes into S115 cells, we show that the expression of the genes is regulated by both androgens and glucocorticoids. Furthermore, hormonal regulation is also conferred by the LTR on the neighboring guanine phosphoribosyltransferase (gpt) gene. Thus, androgens can act on the LTR of MMTV when the appropriate receptors are present in the cells, and this interaction can influence the expression of additional adjacent genes.

Serum-free growth of adult human prostatic epithelial cells

Proliferation of adult human prostatic epithelial cells in serum-free medium occurs upon the addition of cholera toxin, epidermal growth factor, pituitary extract, and hydrocortisone to basal medium PFMR-4A. Insulin and selenium enhance proliferation and permit growth at lower cell densities. Reducing the level of calcium in the medium dramatically alters morphology and also seems to increase proliferation. Mortal strains of cells derived from normal central or peripheral zone, benign hyperplasia, or cancer respond similarly to growth factors and calcium, but two populations of cancer cells which have been long-lived and may be immortal lines behave differently. GKC-CA cells require serum proteins or high levels of pituitary extract for optimal growth, and neither GKC-CA cells or cells of another cancer line, WB-CA, proliferate well in medium containing reduced levels of calcium. These observations may, however, be a reflection of attachment phenomena rather than of growth responses per se. Growth of cells in serum-free medium has allowed definitive studies of the effects of androgens, and regardless of cell type no response to androgens of prostate epithelial cells under any experimental conditions has been seen.

Transcriptional control of the mouse alpha 2(I) collagen gene: functional deletion analysis of the promoter and evidence for cell-specific expression

A chimeric gene was constructed in which sequences between 2,000 base pairs upstream of the start of transcription of the mouse alpha 2(I) collagen gene and 54 base pairs downstream of this site were fused to the chloramphenicol acetyltransferase (CAT) gene. We present evidence suggesting that this collagen gene segment is sufficient for cell-specific expression of the chimeric gene. Indeed, the levels of CAT activity in transient expression experiments were at least 10 times higher after transfection of NIH 3T3 cells than after transfection of a mouse myeloma cell line, whereas much less difference was found after transfection of these two cell types with pSV2-CAT, a plasmid in which the early simian virus 40 promoter is fused to the CAT gene. Several deletions were introduced in the same 5'-flanking segment of the alpha 2(I) collagen gene, and the effects of these deletions were examined after DNA transfection of the chimeric collagen-CAT gene into NIH 3T3 cells. At least two segments broadly located between -979 and -502 and between -346 and -104 are needed for optimal expression of the chimeric gene. These results were obtained both in transient expression experiments and by analysis of pools of NIH 3T3 cells that were stably transfected with the different mutants. In general, the effects of the deletions on the activity of the alpha 2(I) collagen promoter were analogous, whether the plasmids harbored the simian virus 40 enhancer sequence or not, although the overall levels of expression of the chimeric gene were increased when the recombinant plasmids contained this sequence.

Sequence organisation of rat seminal vesicle F gene: location of transcriptional start point and sequence comparison with six other androgen-regulated genes

Seminal vesicle F gene, encoding an androgen-regulated serine-rich structural protein of the rat copulatory plug, has been sequenced together with 5' and 3' flanking regions. The intron/exon arrangement of the gene deduced from restriction maps was confirmed. The major and possible minor transcriptional start points were located by primer extension analysis and S1 nuclease mapping. A published nucleotide sequence for seminal vesicle S gene which also encodes an androgen-regulated protein of the copulatory plug has been extended to allow comparison of F and S genes. The considerable sequence homology between the two genes confirms their evolutionary relatedness. Homology is especially high in their promoter regions and their transcriptional start points are identical. They share several regions of dyad symmetry including one just upstream of the promoter. The upstream regions of F and S genes were compared with those of five other androgen-responsive rodent genes in an attempt to identify common sequence motifs that might be involved in hormonal regulation of gene expression.

Expression of amplified human beta interferon genes using heavy metal induction in Chinese hamster ovary cells

An expression cassette consisting of the human beta-interferon (beta-IFN) cDNA fused to the human metallothionein (MeT)IIA promoter has been linked to a selectable mouse dihydrofolate reductase gene (dhfr) and used to transform dhfr-deficient Chinese hamster ovary (CHO) cells. Transformants resistant to increasing concentrations of methotrexate (Mtx) were isolated and found to secrete beta-IFN either constitutively or upon induction with cadmium (up to 325 000 units beta-IFN/10(6) cells/24 h). Molecular analysis demonstrates a large increase in beta-IFN-specific DNA sequences and beta-IFN mRNA levels in amplified cell lines, with initiation of transcription occurring at the authentic start point for the MeT promoter.

Organization and expression of genes encoding prostatic steroid binding protein

We have cloned the genes for prostatic steroid binding protein to study the mechanism whereby their expression is regulated by testosterone. The genes for the C1 and C2 polypeptides are probably unique whereas there are two genes C3(1) and C3(2) for the C3 polypeptide of which only the former is transcribed in vivo. The state of DNA methylation associated with the two genes for C3 also differ, insofar as C3(1) is demethylated in ventral prostate from 14-28 days of age, whereas the C3(2) gene remains hypermethylated. The organization of all four genes is similar and appreciable DNA sequence homologies suggest that they may have arisen from a single ancestral gene. To study C3 expression and its hormonal regulation we have introduced the cloned genes into mouse S115 cells, an androgen-responsive cell line. Both genes were accurately transcribed and their expression was stimulated up to fivefold by 10(-8) M testosterone in approximately one third of the clones tested. To delineate the site of action of the hormone we have constructed chimeric genes consisting of putative C3 promoters and regulatory sequences together with a marker gene, interferon. This chimeric gene resulted in interferon production but its expression was stimulated by less than twofold in all clones tested. Therefore, these results indicate that, in mouse cells, testosterone does not interact directly with the rat C3 promoter but, in certain clones, may act post-transcriptionally.

Tissue-specific activation of a cloned alpha-fetoprotein gene during differentiation of a transfected embryonal carcinoma cell line

To identify cis-acting DNA elements involved in the activation of the alpha-fetoprotein gene during differentiation, modified copies of the gene were introduced into murine F9 embryonal carcinoma cells. The differentiation of the transformants to either parietal or visceral endoderm was accompanied by induction of the exogenous template in a manner qualitatively, but not quantitatively, identical to that of the endogenous alpha-fetoprotein gene.

Progestin-specific markers in human cell lines: biological and pharmacological applications

We review the progestin-specific responses (induced proteins, increased enzymatic activity) described in uterus, mammary tumours and human breast cancer cell lines established from pleural effusions. Recent data from our laboratory using the T47D breast cancer cell line are then given. They include: (a) a general methodology for evaluating the specific effects of steroids on the production of [35S]methionine-labelled proteins released into the culture medium; (b) results concerning the specificity of regulation by the progestins of a 48 000 dalton protein secreted by T47D cells; (c) the evidence for androgen-specific proteins in the same cells; (d) A discussion of the criteria required to define the receptor responsible for a particular effect of steroids. Lastly, we consider the general interest of progestin-regulated proteins in cell culture for pharmacology and biology.

Rat prostatic steroid binding protein: characterisation of the Alu element upstream of the C3 genes

We have characterised an Alu-like repetitive element found about 400 bp upstream of the gene encoding the C3 component of rat prostatic steroid binding protein and suggest, from comparisons with other published sequences, that it is an example of a third class of rodent Alu-equivalent sequences. Members of this class are 80-90 bp long, share greater than 90% sequence homology, and contain sequences resembling the RNA polymerase III bipartite promoter. The Alu type III element within the C3 gene was found to be expressed in cell-free systems and within heterologous cells stably transfected with the C3 gene, but these transcripts were not detectable in rat ventral prostate. It therefore seems unlikely that expression of this sequence plays a role in expression from the adjacent C3 gene.

Polypeptide hormone regulation of gene transcription: specific 5' genomic sequences are required for epidermal growth factor and phorbol ester regulation of prolactin gene expression

A fusion gene containing 5' rat prolactin genomic sequences ligated to the structural portion of the rat growth hormone gene ( grl ) was introduced by DNA-mediated gene transfer into mammalian cells by using a chimeric plasmid vector. Clonal transfected cell lines produced a mRNA that used the authentic 5' initiation site and that was processed to the predicted size. The intracellular levels of this RNA product were increased 2.5- to 5-fold by exposure of the cells to epidermal growth factor (EGF) and 2- to 3-fold by exposure of the cells to a potent phorbol ester, phorbol 12-myristate 13-acetate, apparently due to regulation at the level of gene transcription. Substitution of the 5' prolactin DNA sequences by 5' growth hormone DNA sequences resulted in the loss of EGF inducibility. A genomic sequence in or near the 5' flanking portion of the prolactin gene therefore appears to confer polypeptide hormone transcriptional regulation upon the gene.

Use of gene transfer to study expression of steroid-responsive genes

The ability to introduce DNA into eucaryotic cells has provided a means to analyse the expression of cloned genes. By manipulating the genes in vitro using recombinant DNA techniques it is possible to identify regulatory DNA sequences which are important for individual steps in gene expression. This review will summarize how these techniques have been applied to study steroid-responsive genes and what we have learned about steroid hormone action.

Interaction of rat prostate androgen receptors with polynucleotides, RNA, DNA and cloned DNA fragments

Androgen receptors were partially purified from prostates of mature (non-castrated) rats by chromatography on 2',5'-ADP-Sepharose and labelled by exchange with 5 alpha-[3H]dihydrotestosterone. The partially purified receptor preparation was free of DNAase activity and sedimented at approx. 3 S. The specificity of the interaction of this androgen receptor with nucleotides was investigated in a competitive binding assay using inhibition of binding of the steroid receptor complex to ADP-Sepharose. Certain polyribonucleotides were strongly bound (e.g., poly(UG), poly(AU), poly(G) and poly(U] and competed more effectively for the receptor binding sites than prostate RNA. Restriction fragments of genomic clones from the genes which code for prostatic binding protein showed only moderate affinity for the 3 S receptor form. These data suggest that the 3 S form of the androgen receptor lacks the specific domain or conformation necessary for specific interaction with DNA, but retains a high affinity for certain forms of RNA. Some potent inhibitors of proteolysis (diisopropylfluorophosphate, leupeptin) did not have any effect on the form of the receptor isolated from mature intact animals. A possible function of the 3 S form in post-transcriptional processing is discussed.

Steroid controlled expression of the chicken lysozyme and the rat tryptophan oxygenase gene after transfer into eukaryotic cells

To study the mechanism of steroid induced transcriptional control we have introduced recombinants of the chicken lysozyme gene and the rat tryptophan oxygenase (TO) gene into heterologous and homologous cells. To monitor the activity of the TO-promoter, 1.9 kb of the TO 5'-flanking sequences were fused with sequences coding for the bacterial enzyme chloramphenicol acetyltransferase (CAT). Upon transfer into mouse L-cells the transient expression of the TO-CAT recombinant was found to be inducible by dexamethasone. Transient expression of chicken lysozyme gene recombinants after introduction into various cell types could only be detected in chicken oviduct cells, or in conjunction with SV-40 enhancer sequences in human cells. The recombinant gene used in oviduct cells was a fusion between the lysozyme promoter, including 1.4 kb of upstream sequences, and the coding region of the gene for SV 40 T-antigen (plys-T). The expression in oviduct cells was stimulated by dexamethasone or progesterone, whereas SV 40 enhanced expression of lysozyme sequences in human cells could not be regulated by steroids. Using several deletion mutants, a region between -220 bp and -140 bp upstream of the cap site was found to be essential for both regulation by glucocorticoids as well as by progesterone.

Organization and expression of prostatic steroid binding protein genes

The function of regulatory regions of DNA, which flank the genes for prostatic steroid binding protein, is being analysed by introducing the cloned genes into heterologous cells. Two non-allelic genes for the C3 polypeptide, C3(1) and C3(2) have been transfected into androgen-responsive S115 cells using SV2-gpt vectors. The genes have been introduced either intact or as so-called fusion genes consisting of putative C3 promoters plus human beta-interferon cDNA. Both genes for C3 were accurately transcribed and their expression was stimulated 5-10-fold with 10(-8) M testosterone. Thus we should be able to define at least one region of DNA which confers androgen sensitivity to the genes. Although both genes were expressed similarly in S115 cells only C3(1) is responsible for C3 in vivo and C3(2) is transcribed poorly, if at all. The most likely explanation for the difference is that in vivo the C3(2) gene remains hypermethylated whereas the DNA which was introduced into S115 cells was unmethylated. This result supports the notion that the state of DNA methylation is important for controlling the transcription of genes.