ABSTRACT
cDNA clones coding for rabbit prolactin were isolated from a pituitary library using a rat prolactin RNA probe. One cDNA contained 873 bases including the entire coding sequence of rabbit prolactin, its signal peptide and the 5' and 3' untranslated regions of 44 and 145 nucleotides respectively. The deduced amino acid sequence of the cloned prolactin cDNA presented a 93-78% identity with mink, porcine and human prolactins. The prolactin gene transcription was investigated by RT-PCR analysis in several organs of midlactating New Zealand White rabbits. The ectopic transcription of the prolactin gene was examined in more detail in the mammary gland. A strong PCR signal was detected in the mammary gland of virgin does and was also observed during pregnancy and at the beginning of lactation. This PCR signal was very weak in mid-lactating and absent in post-weaning mammary gland.
Subject(s)
Lactation/metabolism , Mammary Glands, Animal/metabolism , Pituitary Gland/metabolism , Pregnancy, Animal/metabolism , Prolactin/biosynthesis , Amino Acid Sequence , Animals , Base Sequence , Cattle , Cloning, Molecular , DNA Primers , DNA, Complementary , Female , Gene Expression Regulation , Gene Library , Humans , Mink , Molecular Sequence Data , Pregnancy , Prolactin/chemistry , Rabbits , Rats , Sequence Homology, Amino Acid , Sheep , SwineABSTRACT
The extracellular domain of the PRL receptor (PRL-R) is composed of two subdomains of approximately 100 amino acids, S1 and S2. To explore the functional significance of these subdomains in PRL binding and signal transduction, deletion mutants of S1 or/and S2 subdomains were constructed. We report here the inability of each of these mutant receptor forms to bind PRL after expression in COS-7 cells. We also studied the abilities of these different mutant receptors to respond to hormonal stimulation after transfection of each mutant complementary DNA into CHO-K1 cells along with a chimeric gene containing the promoter of a milk protein gene (beta-lactoglobulin) fused to chloramphenicol acetyltransferase coding sequence. Somewhat unexpectedly, a constitutively (PRL-independent) mutant form of the PRL-R was obtained after deletion of the S2 subdomain. Moreover, we analyzed, in CHO-K1 cells, the biological activity of chimeric receptors constructs in which each subdomain sequence was replaced by an unrelated, but coding, sequence of foreign protein, and we confirmed a specific requirement for the S1 sequence in the constitutive activity. In contrast, the S2 subdomain produced an inhibitory effect on S1 constitutive activity. Cotransfection experiments with the wild-type receptor and the constitutive mutant receptor provided evidence that the wild-type receptor was able to inhibit the constitutive activity of the deleted mutant. Furthermore, in the mouse mammary epithelial cell line HC11, the constitutive PRL-R form was able to induce transcription of the beta-casein gene in the absence of PRL. These results suggest a complex signal transduction process that implicates each extracellular PRL-R subdomain. Possible mechanisms for the constitutive effect are discussed.
Subject(s)
Mutagenesis, Site-Directed , Receptors, Prolactin/chemistry , Receptors, Prolactin/metabolism , Animals , CHO Cells , Caseins/genetics , Cell Line , Chloramphenicol O-Acetyltransferase/genetics , Cricetinae , DNA, Complementary/genetics , Gene Expression , Prolactin/metabolism , Promoter Regions, Genetic , Receptors, Prolactin/genetics , Recombinant Fusion Proteins , Signal Transduction , Structure-Activity Relationship , Swine , TransfectionABSTRACT
The Androgen Receptor (AR) mRNA was studied in cultured cells from normal subjects and 10 patients with Complete (CAI, 9 patients, 5: R-, 4: R+) or Partial (PAI, 1 patient) Androgen Insensitivity. The probe was a 3,4 cDNA coding for the entire AR. AR mRNA appears as a 10 kb band. It is strongly expressed in genital skin fibroblasts, 50 to 100 times less in non genital skin. In genital skin fibroblasts, a 3 to 5 fold increase is observed after 1 h of treatment of the cultures with dihydrotestosterone (DHT, 5 nM) whereas a 22 fold decrease is observed after 24 h. A 3 fold increase is also observed after 1 h of treatment with progesterone (50 nM) or cyproterone acetate (500 nM) which does not seem to act as an antiandrogen in this model. The 10 kb band was present in all 10 A1 patients studied, though expressed at a much lower level. It is therefore possible that an abnormal regulation of the AR gene expression is involved in the mechanism of Androgen Insensitivity.
