Characterization of monoclonal antibodies specific for the V beta 3 family of the human T cell receptor generated using soluble TCR beta-chain

A soluble, recombinant form of the human T cell receptor (TCR) beta-chain containing the V beta 3.1 sequence has been constructed, expressed in Chinese hamster ovary cells, amplified by dihydrofolate reductase selection, and purified in quantities appropriate for the generation of monoclonal antibodies (mAb). The V beta 3 sequence was chosen because of its reported elevated usage in the synovial T cells of rheumatoid arthritis patients but the approach described should be applicable to other known human V beta gene sequences. By this method, two mAb were prepared which reacted with up to 10% of normal, live peripheral blood T cells but with reactivity varying greatly among individual donors. Both mAb specifically bound to a murine T cell line transfected with a human TCR V beta 3.1 and immunoprecipitated a protein of the expected molecular weight for the TCR beta-chain. Both antibodies were mitogenic for T cells and analysis of peripheral blood lymphocyte cultures stimulated with the mAb suggested that both were specific for the V beta 3.1 subfamily and not D beta or J beta. Clones expressing V beta 3, which were derived from mAb-stimulated peripheral blood lymphocytes of a single individual, preferentially (8/13), but not exclusively, utilized the J beta 2.7 gene segment. The V beta 3.1 usage showed no preference for the CD8+ or CD4+ subpopulations of normal peripheral blood T cells.

Steroid requirement for androgen receptor dimerization and DNA binding. Modulation by intramolecular interactions between the NH2-terminal and steroid-binding domains

Infection of Spodoptera frugiperda Sf9 insect cells with recombinant human androgen receptor (AR) baculovirus results in expression of a 118-kDa phosphoprotein that displays high affinity androgen binding and androgen-dependent targeting to the nucleus. Using the DNA mobility shift assay, specific in vitro binding of full-length AR to androgen response element DNA (ARE) requires intracellular hormone exposure. The ability of a variety of steroids to induce ARE binding paralleled their transcriptional potential. Certain antihormones, cyproterone acetate and RU486, promote ARE binding, but a pure antiandrogen, hydroxyflutamide, inhibits AR binding to ARE DNA. AR dimerization requires incubation of recombinant baculovirus-infected insect cells with androgen, but only when one or both components of the dimer contain the NH2-terminal domain. Based on the intensities of ARE binding and lack of binding to an ARE half-site, it appears that, unlike the glucocorticoid receptor, AR binds DNA primarily as a dimer. Thus, full-length baculovirus-expressed AR requires intracellular hormone exposure for dimerization and ARE binding to overcome inhibition imposed by the AR NH2-terminal domain. Antihormones with agonist activity promote dimerization and ARE binding, while a pure antiandrogen blocks AR DNA binding. It is concluded that intramolecular interactions between the NH2-terminal and steroid-binding domains are regulated by the specificity of hormone binding and modulate receptor dimerization and DNA binding.

Receptor accessory factor enhances specific DNA binding of androgen and glucocorticoid receptors

Protein-protein interactions are common among transcriptional activators and may have important consequences for gene regulation. Using the mobility shift assay, we have identified a factor that enhances specific DNA binding of truncated rat androgen (AR) and glucocorticoid (GR) receptors by 25- and 6-fold, respectively, through the formation of heteromeric complexes. This factor, designated receptor accessory factor, or RAF, also potentiates DNA binding of full-length human GR. RAF is temperature and trypsin sensitive and is present in a variety of cultured mammalian cells. By gel filtration RAF has a predicted molecular mass of 130 kDa. RAF enhancement of AR-DNA binding is optimal with androgen response element DNA. RAF appears to interact directly with AR because 1) deoxycholate, which interferes with protein-protein but not protein-DNA interactions, prevents RAF.AR.DNA complex formation, 2) RAF activity is recovered from an androgen response element DNA affinity column only in the presence of AR, and 3) RAF increases the size of an AR.DNA complex by gel filtration. Mutagenesis of truncated AR fragments indicates that a region in the NH2-terminal domain is required for RAF to enhance AR-DNA binding. The interaction of RAF with AR and GR suggests that RAF might influence the ability of these nuclear receptors to activate transcription.

Transcriptional repression of the glycoprotein hormone alpha subunit gene by androgen may involve direct binding of androgen receptor to the proximal promoter

Testicular androgens suppress the synthesis and secretion of the pituitary gonadotropins, in particular, luteinizing hormone. This suppressive effect includes transcription of both the common alpha subunit gene and the unique beta subunit genes. Herein, we demonstrate that 1500 base pairs (bp) of proximal 5'-flanking region derived from the human alpha subunit gene and a shorter 315-bp segment of the bovine alpha subunit gene confer negative regulation by androgen to the gene encoding bacterial chloramphenicol acetyltransferase in transgenic mice. Cotransfection assays with human androgen receptor indicated that the 1500-bp promoter region of the human alpha subunit gene also confers androgen regulation (transcriptional suppression) to reporter genes in both pituitary and placental cell lines. This raises the possibility of a role for DNA binding in suppression of alpha subunit transcription by activated androgen receptor. Consistent with this possibility, we have used a gel-mobility shift assay to detect several high affinity binding sites for androgen receptor located in the proximal promoter of the human alpha subunit gene. The strongest androgen receptor binding site is located at approximately -101 in the proximal 5'-flanking region. This steroid receptor binding site overlaps another binding site that defines one of several contiguous cis-acting regulatory elements required for basal transcriptional activity. Thus, binding of activated androgen receptor to this region may block the binding of a requisite trans-acting factor and lead to an attenuation in transcription. We conclude that this interaction, which occurs directly at the level of the pituitary, represents one of several physiological avenues through which androgens regulate gonadotropin gene expression.

Characterization of the DNA-binding domain of the mouse uterine estrogen receptor using site-specific polyclonal antibodies

The DNA-binding domain of the mouse uterine estrogen receptor (ER) was characterized using site-specific polyclonal antibodies. The peptides used as antigens have sequences corresponding to amino acids 185-199 and 227-245, the two zinc finger regions of the DNA-binding domain of the human ER, and produced anti-sera designated A-1542 and A-1554, respectively. Mouse uterine nuclear ER and salt-activated 4 S cytosol receptor, as well as 8 S untransformed cytosol receptor, were observed to react with the antisera by Western blot and sucrose density gradient centrifugation analyses indicating that the DNA-binding domain of the 8 S cytosol receptor is not completely masked by heat shock protein 90 or other proteins. Only A-1554 detected a nuclear-specific doublet form of the ER on Western blot analysis. In a gel shift assay, neither antisera altered the pattern of the nuclear ER interaction with the vitellogenin A2 estrogen response element (VRE). In contrast, antiserum A-1554 partially shifted the 8 S cytosol receptor-VRE complex. This concurs with mutational analysis and x-ray crystallography studies with the human ER that have shown that the second finger is not in contact with the DNA. The results of the gel shift assay were confirmed by sucrose density gradient analysis using the same buffer conditions. The nuclear receptor-VRE complex did not react with either antisera, suggesting that when the dimeric nuclear receptor form binds the VRE, the specific receptor epitopes involved with the DNA binding may be blocked and unable to bind the antisera. The cytosol receptor-VRE complex reacted only partially with the second finger antisera A-1554, suggesting that on receptor monomers the second finger epitope is not completely blocked by DNA binding or dimer formation.

Immunohistochemistry of the androgen receptor in human benign and malignant prostate tissue

The role of the androgen receptor in the development and progression of prostatic carcinoma has not been defined. The development of androgen receptor antibodies has provided new opportunities for direct immunohistochemical analysis. We compared the androgen receptor staining characteristics of fresh human prostatic carcinoma with benign prostatic hyperplasia (BPH) using an avidin-biotin complex method. Cancer and BPH obtained from the same radical retropubic prostatectomy specimen in 10 prostate cancer patients (68.5 +/- 7.3 years old standard deviation) and BPH from 10 noncancer patients (71.5 +/- 7.7 years old) were incubated with AR52, a rabbit polyclonal antibody against a synthetic androgen receptor peptide. Nuclei within each section were graded for intensity of androgen receptor staining (0-absent, 1-weak, 2-moderate or 3-strong) and the percentage (0 to 100%) of nuclei sampled staining at each of these intensity levels was determined. A total intensity score (0 to 300) was the summation of the products of each intensity score (0 to 3) and their corresponding percentages. Cancer sections (166 +/- 69) stained less intensely and more heterogeneously than BPH in cancer patients (246 +/- 41, Student's t test p < 0.05) and noncancer patients (225 +/- 39, p < 0.05). The decreased intensity and greater heterogeneity of androgen receptor staining in cancer tissue may implicate a quantitative or functional difference in androgen receptor between prostatic carcinoma and BPH.

Single base mutations in the human androgen receptor gene causing complete androgen insensitivity: rapid detection by a modified denaturing gradient gel electrophoresis technique

Mutations of the human androgen receptor (AR) gene impair normal sexual differentiation and development in karyotypic males, resulting in a spectrum of external genital phenotypes ranging from complete female to nearly complete male. Identification and characterization of these mutations can provide valuable information regarding the functional importance of specific amino acids of the AR. To screen for point mutations in the AR gene underlying the phenotypic abnormalities in the androgen insensitivity syndrome (AIS), the eight exons of the AR gene were amplified from genomic DNA using the polymerase chain reaction (PCR) and analyzed by denaturing gradient gel electrophoresis. A computer program, MELTMAP, was used to identify optimum sequences for denaturing gradient gel electrophoresis, and mutation detection sensitivity was enhanced by forming heteroduplexes between control and subject PCR products to create base mismatches. In seven families with complete AIS, single base mutations were found in the region of the AR gene encoding the steroid-binding domain of the receptor. The mutations that converted amino acid 774 from Arg to His and amino acid 864 from Asp to Gly were recreated using site-directed mutagenesis and the mutant ARs expressed in COS 7 and CV1 cells. In both cases, abnormalities of androgen binding and transcriptional activation were consistent with the observed sex phenotype. These results together with others reported previously demonstrate that single amino acid changes within the region encoded by exons D to H of the AR gene can alter androgen binding and are a common cause of complete androgen resistance. The strategy used herein, employing denaturing gradient gel analysis of heteroduplex PCR products, provides a valuable aid to rapid detection of single base mutations in AIS.

Ligand-independent oligomerization of natriuretic peptide receptors. Identification of heteromeric receptors and a dominant negative mutant

Activation of many single-transmembrane receptors requires ligand-induced receptor oligomerization. We have examined the oligomerization of the atrial natriuretic peptide receptor, NPR-A, using epitope-tagged receptor in a co-immunoprecipitation assay. Unlike other single-transmembrane receptors, NPR-A oligomerized in a ligand-independent fashion. Extracellular receptor sequences were both necessary and sufficient for oligomer formation. NPR-A was also able to oligomerize with the related natriuretic peptide receptor, NPR-B. A truncated NPR-A lacking most of the cytoplasmic domain blocked activation of the full-length receptor, presumably through formation of an inactive heteromer. These results indicate that oligomerization of this single-transmembrane receptor is important for the transduction of a conformational change across the plasma membrane but are not consistent with models in which natriuretic peptide receptor oligomerization serves merely to bring intracellular domains together.

Domain functions of the androgen receptor

Molecular cloning of the androgen receptor cDNA has facilitated analysis of structure/function relationships of this ligand activated transcription factor. Amplification of mutant androgen receptor DNA using the polymerase chain reaction has revealed single base and deletion mutations in the androgen receptor gene that cause the androgen insensitivity syndrome in rats and humans. Site directed mutagenesis of the NH2-terminal and hinge regions indicates specific sequences required for full transcriptional activation and nuclear targeting of the androgen receptor. Finally, transient transfection systems have shown that the antiandrogen cyproterone acetate is both an agonist and antagonist, while hydroxyflutamide acts only as an antagonist and thus is a pure antiandrogen.

Complete androgen insensitivity due to deletion of exon C of the androgen receptor gene highlights the functional importance of the second zinc finger of the androgen receptor in vivo

Androgen-dependent gene transcription is mediated by the androgen receptor (AR) through interaction of its central zinc finger region with specific DNA sequences on target genes. Failure of this receptor-mediated gene transcription results in end organ resistance to androgens-the androgen insensitivity syndromes. In a pair of siblings with complete androgen insensitivity who had supranormal levels of androgen binding in genital skin fibroblasts, polymerase chain reaction and Southern blot analysis of the androgen receptor gene confirmed by polymerase chain reaction and sequence analysis of AR cDNA, revealed an in-frame deletion of exon C encoding the second zinc finger of the receptor. The mutant receptor in cultured genital skin fibroblasts had normal androgen binding affinity and was localized in the nucleus but had markedly reduced DNA-binding affinity. When recreated in vitro and tested in a cotransfection assay system the mutant receptor failed to activate transcription of an androgen-responsive reporter gene. This naturally occurring mutation highlights the functional dependence of the AR upon its second zinc finger in vivo and explains the complete insensitivity to androgen manifest by the affected individuals despite increased androgen binding. The elevated AR levels in the subjects' genital skin fibroblasts further suggests a possible role for the second zinc finger in autoregulation of receptor levels in vivo.

Molecular cloning of rat prostate transglutaminase complementary DNA. The major androgen-regulated protein DP1 of rat dorsal prostate and coagulating gland

Complementary DNA (cDNA) that codes for a major androgen-dependent secretory protein of rat coagulating gland and dorsal prostate, dorsal protein 1 (DP1), was isolated by molecular cloning. Recombinant DP1 cDNA clones were identified from a bacteriophage lambda gt11 rat coagulating gland expression library using an affinity purified polyclonal antibody. Amino acid sequence deduced from DNA contained sequences identical with several DP1 cyanogen bromide cleavage fragments. Northern blot hybridization of poly(A) RNA isolated from intact rat dorsal prostate and coagulating gland revealed a predominant messenger RNA (mRNA) species of approximately 3200 nucleotides. Tissue-specific expression of DP1 mRNA was indicated by the absence of DP1 mRNA in ventral prostate and other tissues of the rat. Expression of DP1 mRNA was androgen-dependent, decreasing approximately 80% 7 days after castration and increasing rapidly following androgen replacement. Southern blot analysis of restriction enzyme-digested rat DNA indicated that DP1 is encoded by a single gene and that no major genomic rearrangements accounted for its lack of expression in the dorsal prostate-derived rat Dunning tumor. Sequence comparisons revealed that rat prostate DP1 shares sequence identity with Factor XIIIa and tissue transglutaminase, including the active center, GQCWVF, indicating that DP1 is a member of the transglutaminase gene family.

Complete deletion of the androgen receptor gene: definition of the null phenotype of the androgen insensitivity syndrome and determination of carrier status

The molecular basis of androgen insensitivity was investigated in a family with the complete form of the syndrome. Polymerase chain reaction amplification and Southern blot analysis of genomic DNA revealed a deletion of the entire androgen receptor (AR) gene in affected individuals. The carrier status of female members of this family was examined using a HindIII restriction fragment length polymorphism associated with the AR gene. Obligate carriers were hemizygous for one of the two alleles at this locus, while heterozygosity for the polymorphic alleles, implying the presence of two copies of the AR gene, indicated noncarrier status. This conclusion was supported by gene dosage studies using comparative densitometric analysis of Southern blots hybridized simultaneously with an AR cDNA probe and a control cDNA probe from an unrelated gene. Finally, the pattern of inheritance of another X-linked DNA polymorphism allowed us to conclude that the original mutation had occurred in the germ line of the maternal great-grandfather of the index patient. Although rare, complete deletion of the AR gene is of particular importance in terms of correlation between molecular defect and phenotype, as it represents the quintessential form of complete androgen insensitivity, the null phenotype.

Immunocytochemical localization of androgen receptors in the male songbird and quail brain

The distribution of androgen receptors was studied in the brain of the Japanese quail (Coturnix japonica), the zebra finch (Taeniopygia guttata), and the canary (Serinus canaria) by immunocytochemistry with a polyclonal antibody (AR32) raised in rabbit against a synthetic peptide corresponding to a sequence located at the N-terminus of the androgen receptor molecule. In quail, androgen receptor-immunoreactive cells were observed in the nucleus intercollicularis and in various nuclei of the preoptic-hypothalamic complex, namely, the nucleus preopticus medialis, the ventral part of the nucleus anterior medialis hypothalami, the nucleus paraventricularis magnocellularis, the nucleus ventromedialis hypothalami, and the tuberal hypothalamus. In the two songbird species, labeled cells were also observed in various nuclei in the preoptic-hypothalamic region, in the nucleus taeniae, and in the nucleus intercollicularis. Additional androgen receptor-immunoreactive cells were present in the androgen-sensitive telencephalic nuclei that are part of the song control system. These immunoreactive cells filled and outlined the boundaries of the hyperstriatum ventrale, pars caudalis, nucleus magnocellularis neostriatalis anterioris (both in the lateral and medial subdivisions), and nucleus robustus archistriatalis. The immunoreactive material was primarily present in cell nuclei but a low level of immunoreactivity was also clearly detected in cytoplasm in some brain areas. These studies demonstrate, for the first time, that androgen receptors can be detected by immunocytochemistry in the avian brain and the results are in general agreement with the binding data obtained by autoradiography with tritiated dihydrotestosterone. Immunocytochemical methods offer several advantages over autoradiography and their use for the study of the androgen receptor will greatly facilitate the analysis of steroid-sensitive systems in the avian brain.

Response elements of the androgen-regulated C3 gene

Intron and 5'-flanking regions of the androgen-regulated C3 subunit gene contain potential cis-acting transcription control sequences including several 15-base pair (bp) partial palindromes resembling response elements for glucocorticoid (GRE) and progesterone (PRE) receptors. Specific DNA binding of the androgen receptor (AR) and androgen-dependent activation of transcription indicate that some of these GRE/PRE-like sequences are capable of functioning as androgen response elements (ARE). A 0.3-kilobase pair (kbp) 5'-flanking fragment including the promoter region contains one such sequence (element A) and a 0.5-kbp region of the first intron contains two sequences (elements B and C). Androgen-dependent enhancement of transcription was assayed by cotransfection of CV1 cells with a rat AR expression vector, pCMVrAR, and C3 genomic fragments or synthetic elements cloned into the reporter vector ptkCAT. Enhancement of chloramphenicol acetyltransferase activity with the 0.5-kbp first intron fragment was 16 +/- 4-fold, while with the 0.3-kbp 5'-flanking fragment no response was detected and element C alone was greater than B or A. Binding of AR in the mobility shift assay correlated with androgen-dependent enhancement of chloramphenicol acetyltransferase activity. The intensity of transcriptional enhancement with the 0.5-kbp intron fragment suggested that other regulatory sequences within this intron region potentiated the ARE activities of elements B and C. ARE activity of the strongest C3 gene response element (C) was similar to that of a potent GRE (element M) of the mouse mammary tumor virus gene.

Androgen receptor phosphorylation, turnover, nuclear transport, and transcriptional activation. Specificity for steroids and antihormones

Nuclear transport, phosphorylation, ligand binding, and degradation rate of the recombinant androgen receptor (AR) were analyzed in transfected COS cells in the presence of various steroids and antiandrogens. Transcriptional activation was assessed in CV1 cells by cotransfection with an androgen-responsive chloramphenicol acetyltransferase (CAT) reporter vector. Hormone binding specificity of recombinant AR was essentially identical to endogenous AR. AR localized in the nucleus in the presence of methyltrienolone (R1881, a synthetic androgen), dihydrotestosterone, testosterone, hydroxyflutamide, cyproterone acetate, estradiol, progesterone, and RU486. In the absence of hormone or with the antiandrogen, flutamide, AR remained largely in the cytoplasm with a perinuclear distribution. AR was degraded rapidly (t1/2 = 1 h) except in the presence of androgen (t1/2 = 6 h) which accounted for an apparent 2-4-fold androgen-induced increase in AR phosphorylation, indicating that AR phosphorylation was not enhanced by androgen. CAT activity was stimulated by R1881, dihydrotestosterone, testosterone, cyproterone acetate, estradiol, progesterone, and RU486 in a dose-dependent manner. The antiandrogens, flutamide and hydroxyflutamide, lacked agonist activity and inhibited R1881-induced activation of CAT and androgen stabilization of AR. Steroids and antiandrogens with moderate to low affinity for AR promoted both nuclear transport and transcriptional activation but only at high hormone concentrations. Hydroxyflutamide acted as a true antiandrogen since it lacked agonist activity and was an inhibitor of androgen-induced transcriptional activation.

An androgen-inducible expression system for Saccharomyces cerevisiae

A novel controllable expression system for Saccharomyces cerevisiae has been developed. Expression of the gene encoding the human androgen receptor, from a strong yeast promoter, results in transactivation of a hybrid promoter carrying androgen-responsive sequences such that a target gene may be expressed in an androgen-dependent manner. By selection of an appropriate combination of androgen receptor level, target-gene copy number and concentration of the androgenic ligand, dihydrotestosterone, the expression level can be set within a 1400-fold range with no detectable effect on normal cell growth.

The multistep proteolytic maturation pathway utilized by vaccinia virus P4a protein: a degenerate conserved cleavage motif within core proteins

The most abundant vaccinia virus (VV) core protein found within the virion is protein 4a, which represents approximately 14% of the particle's dry weight. The 4a protein is synthesized as a 102.5-kDa precursor, which is proteolytically processed to a 62-kDa product concomitant with virion assembly. To identify the pathway by which P4a is converted into 4a, immunological reagents which are specific for subregions of the P4a precursor were developed and used in concert with peptide mapping and protein sequencing procedures. The results obtained suggest that the 891 amino acid P4a precursor is cleaved at two locations, between residues 614 and 615 and 697 and 698. Both the large amino-terminal 4a protein (residues 1-614) and the carboxy-terminal-derived 23-kDa protein (residues 698-891) become major virion constituents. The location and fate of the small internal peptide (residues 615-697) is not known. Interestingly, an analysis of the predicted amino acid sequences at the sites of cleavage within the P4a precursor indicated the presence of an Ala-Gly decreases Thr motif flanking the 697-698 site and an Ala-Gly decreases Ser motif flanking the 614-615 site. Since both of these signals are quite similar to the Ala-Gly decreases Ala signal previously identified as the cleavage point within the VV P4b and P25K core protein precursors (VanSlyke et al., 1991.J. Gen. Virol. 72, 411-416), this suggests that processing of all three core protein precursors may be coordinately linked and/or catalyzed by the same proteinase during viral assembly.

Androgen receptor gene mutations in X-linked spinal and bulbar muscular atrophy

X-linked spinal and bulbar muscular atrophy (Kennedy's disease) is an adult-onset form of motorneuron disease which may be associated with signs of androgen insensitivity. We have now investigated whether the androgen receptor gene on the proximal long arm of the X chromosome is a candidate gene for this disease. In patient samples we found androgen receptor gene mutations with increased size of a polymorphic tandem CAG repeat in the coding region. These amplified repeats were absolutely associated with the disease, being present in 35 unrelated patients and none of 75 controls. They segregated with the disease in 15 families, with no recombination in 61 meioses (the maximum log likelihood ratio (lod score) is 13.2 at a recombination rate of 0). The association is unlikely to be due to linkage disequilibrium, because 11 different disease alleles were observed. We conclude that enlargement of the CAG repeat in the androgen receptor gene is probably the cause of this disorder.

Assembly and analysis of a functional vaccinia virus "amplicon" containing the C-repeat region from the M protein of Streptococcus pyogenes

Previous studies have shown that when inoculated intranasally into mice, vaccinia virus (VV) recombinants expressing the carboxyl half of the Streptococcus pyogenes M protein [which contains the C-repeat region (CRR)] could elicit a protective immune response against subsequent challenge by both homologous and heterologous serotypes of pathogenic group A streptococci. In the present study, an insertion plasmid was constructed that contained three tandem in-frame repeats of a 310-base-pair DNA sequence encoding the CRR from streptococcal M6 protein under control of a constitutive viral promoter. The plasmid was used to introduce the bacterial sequences into the VV genome by homologous recombination. Surprisingly, the recombinant VV:CRR3X virus that was isolated appeared to represent not an individual recombinant virus but a complex mixture of variants that contained from 1 to greater than 20 tandem copies of the CRR region at the insertion site. This genomic complexity was mirrored at the transcriptional level in that a nested set of coterminal transcripts was detected in VV:CRR3X-infected cells, which increased in size from 1400 to 6600 bases by increments of approximately 300 bases. All transcripts containing two or more CRR inserts appeared functional, as Western (immuno) blot analyses of VV:CRR3X-infected cell extracts revealed a family of CRR-related proteins with apparent molecular masses that increased from 30 kDa upward in increments of 10 kDa. All data are consistent with the hypothesis that variation in the VV:CRR3X recombinants is from random crossover events that occur within the CRR region during viral DNA replication. These results suggest that the genomic diversity generated by the "recombinogenic" properties of vaccinia recombinants containing tandem foreign inserts could be used to facilitate induction of a broadly protective immune response against antigenically diverse pathogenic agents.

A frameshift mutation destabilizes androgen receptor messenger RNA in the Tfm mouse

A composite mouse androgen receptor DNA sequence was obtained by amplifying genomic DNA or cDNA using the polymerase chain reaction. The open reading frame was 2,697 basepairs, encoding a polypeptide of 899 amino acids (98,204 mol wt). Amino acid sequence comparisons indicated that the mouse androgen receptor (AR) is 97% homologous with rat AR and 83% with human AR. The amino acid sequences of the three receptors are identical within the DNA- and steroid-binding domains. Northern blot analysis revealed the predominant mouse AR mRNA to be 10 kilobases (kb). A 1.7-kb mRNA species was detected in mouse kidney using a cDNA probe containing only 5' untranslated AR sequence. Lack of hybridization with AR-coding sequence probes suggested that the 1.7-kb mRNA was not a truncated form of AR mRNA. Sequencing of genomic DNA isolated from testicular feminized (Tfm) mice revealed a single base deletion in the N-terminal domain, resulting in a frameshift mutation. Cycloheximide treatment caused a dramatic increase in AR mRNA in kidneys of Tfm mice, but not wild-type mice, suggesting that the Tfm mutation results in an unstable AR mRNA.