SEQUENCE-ANALYSIS OF THE TURKEY LH BETA-SUBUNIT AND ITS REGULATION BYGONADOTROPIN-RELEASING-HORMONE AND PROLACTIN IN CULTURED PITUITARY-CELLS

cDNAs encoding the precursor molecule of the turkey LH beta subunit (t LH beta) were cloned from a turkey pituitary cDNA library. The nucleot ide sequence of the longest of two different tLH beta cDNA clones cont ained 592 bp, and included 23 bp of the 5' untranslated region (UTR) a nd 92 bp of the 3' UTR in addition to a 477 bp open reading frame that encoded a 39 amino acid leader polypeptide and a 120 amino acid matur e apoprotein. Turkey and chicken LH beta sequences shared approximatel y 92 and 93% nucleotide and amino acid sequence similarities respectiv ely. Northern blot analysis of total cellular anterior pituitary RNA s howed that an approximate 800 base transcript hybridized to a P-32-lab elled tLH beta cDNA probe. The gonadotrophin-releasing hormone (GnRH)- and prolactin (PRL)-regulated expression of LH and PRL in dispersed p ituitary cells was determined by Northern blot analysis of tLH beta an d PRL steady-state mRNA levels and by RIA analysis of secreted LH and PRL. GnRH-treated cells showed increased levels of both tLH beta mRNA and secreted LH, whereas mRNA and secreted levels of PRL did not chang e significantly. Cells treated with PRL showed lower levels of tLH bet a and PRL mRNA as well as decreased release of LH and PRL. When cells were treated with both PRL and GnRH, increases in tLH beta mRNA and se creted levels of LH observed with GnRH alone were negated, whereas the decreases in mRNA and secreted levels of PRL observed with PRL alone were abrogated. These findings suggest that PRL can down-regulate tLH beta gene expression and spontaneous release of LH as well as autoregu late PRL gene expression and spontaneous release of PRL, while GnRH ap pears capable of modulating the effects of PRL-regulated LH and PRL ge ne expression and spontaneous release.