Cloning of rat Sertoli cell follicle-stimulating hormone primary response complementary deoxyribonucleic acid: regulation of TSC-22 gene expression.

The molecular mechanisms underlying the pleiotropic effects of FSH were investigated by screening a plasmid cDNA library for clones hybridizing to FSH-regulated RNAs. Recombinant colonies were selected at random, and plasmids were purified, radiolabeled, and hybridized to Northern blots containing RNA extracted from control and FSH-treated Sertoli cells. Of 210 clones screened by this method, 10 hybridized to transcripts that were regulated either positively or negatively by FSH. DNA sequence comparisons with the GenBank database revealed that 3 clones that hybridized to positively regulated RNAs have sequences similar to known or putative transcription regulating factors. Clone 99 encodes the rat homolog of transforming growth factor-beta 1-stimulated clone 22 (TSC-22), which contains a putative leucine zipper region. Clone 18 has 93% sequence identity in the coding region with the cDNA for mouse nuclear factor-kappa B p50 subunit. Clone 325 encodes rat TIS11b, which contains zinc finger-like motifs thought to confer DNA-binding capacity. Among the other cDNAs, 2 have strong sequence similarity to RNA-binding proteins, including splicing factors, 1 corresponds to the rat mitochondrial transcript that encompasses the abundant 12S and 16S ribosomal RNAs, and another has 93% homology with the human B-cell translocation gene-1 (BTG-1), which encodes a putative antiproliferative factor. The remaining 3 clones had no identity with sequences in the GenBank database. Regulation of rat TSC-22 mRNA was analyzed in primary Sertoli cell cultures. TSC-22 mRNA transiently increased 4-fold in the presence of FSH, reached maximal levels at 3 h, and returned to prestimulation levels by 12 h. The FSH-stimulated increase was independent of protein synthesis because it occurred in the presence of cycloheximide and FSH. TSC-22 mRNA was detected in all tissues examined in male and female rats, and the highest levels in the 16-day animal were observed in the testis, ovary, uterus, and lung. Testicular 1.8-kilobase (kb) TSC-22 mRNA decreased by 50% from 14 to 60 days of age. A 5-kb transcript became detectable by 30 days and decreased after 50 days of age. Ovarian 1.8-kb TSC-22 transcript levels increased about 2-fold during the same maturation period.

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