FOLLICLE-STIMULATING-HORMONE (FSH) STIMULATES TRANSFERRIN GENE-TRANSCRIPTION IN RAT SERTOLI CELLS - CIS AND TRANS-ACTING ELEMENTS INVOLVED IN FSH ACTION VIA CYCLIC ADENOSINE-3',5'-MONOPHOSPHATE ON THE TRANSFERRIN GENE

FSH is a major regulator of transferrin (Tf) production in the testis. FSH effects on Sertoli cell Tf production are believed to be mediated, at least in part, via cAMP second messenger system. Previously, it has been shown that FSH and (Bu)2cAMP stimulate Tf mRNA levels. This study examines the effect of cAMP and FSH on Tf gene transcription using run-on assays. These data demonstrate rapid induction of Tf gene by (Bu)2cAMP (2.3-fold) and FSH (2.8-fold) within 30 min and 2 h, respectively. Furthermore, the ability of (Bu)2cAMP and FSH to drive the transcription of chimeric constructs containing a 0.6-kilobase segment of the 5'-regulatory region of the human Tf gene coupled to a chloramphenicol acetyltransferase (CAT) was examined. Deletion analysis indicated that the sequence -100/-52 base pairs is required for the cAMP-dependent transcription. This sequence shows no homology to that of the consensus cAMP-regulatory element (CRE). However, co-transfection experiments with a CRE-binding protein (CREB) expression vector revealed a basal induction of the Tf transcriptional activity as well as a synergistic activation of CREB and (Bu)2cAMP. Expression of KCREB, a dominant negative mutant form of CREB, completely blocked the cAMP induction of the -100+39Tf-CAT construct. This region contains two functional regions PRI and PRII. Gel shift assay with nuclear proteins from Sertoli cells using the PRII and PRI probes showed that the bandshifts formed by PRII were competable complexes with CRE, and a CREB antiserum retarded the migration of nuclear Sertoli cells proteins. We conclude that CREB is implicated in the FSH regulation on the Tf gene in Sertoli cells.