Molecular Endocrinology, Vol 7, 561-569, Copyright © 1993 by Endocrine Society

ARTICLES

Transcriptional regulation of inhibin beta B messenger ribonucleic acid levels in TM.4 or primary rat Sertoli cells by 8-bromo-cyclic adenosine monophosphate

H Najmabadi, LA Rosenberg, QX Yuan, G Reyaz and S Bhasin
Division of Endocrinology, Harbor-University of California-Los Angeles Medical Center, Torrance 90502.

FSH, a major regulator of inhibin production in the testis, is believed to exert its effects via cAMP second messenger system. Inhibin alpha- subunit gene appears to be regulated by cAMP and has a palindromic cAMP response element sequence TGACGTCA. However, the regulation of the inhibin beta B-subunit gene by cAMP has been less clear. It has been assumed that beta B may not be regulated by cAMP, based mainly on observations that FSH stimulates only alpha, not beta B, mRNA levels, and that the 5'-up-stream regulatory region of the beta B gene does not contain the classical cAMP response element. However, we have observed that 8-bromo-cAMP stimulates beta B mRNA levels in both primary Sertoli (approximately 2-fold) and TM.4 cells (approximately 5-fold). We examined whether this cAMP-induced increase in beta B mRNA levels is the result of increased transcription or altered mRNA stability. Data from nuclear run-on assays demonstrate about a 2-fold increase in relative mRNA synthesis rates in primary Sertoli-cells and about a 4- to 5-fold increase in TM.4 cells. Transfection studies in TM.4 and JEG.3 cell lines with beta B:luciferase chimeric reporter gene constructs containing 1.5 kilobases of the beta B 5'-up-stream regulatory region revealed marked cAMP induction of reporter gene activity in both cell types.(ABSTRACT TRUNCATED AT 250 WORDS)

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