CCAAT enhancer-binding protein β and GATA-4 binding regions within the promoter of the steroidogenic acute regulatory protein (StAR) gene are required for transcription in rat ovarian cells

Eran Silverman, Sarah Eimerl, Joseph Orly*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

175 Scopus citations

Abstract

Steroidogenic acute regulatory protein (STAR) iS a vital accessory protein required for biosynthesis of steroid hormones from cholesterol. The present study shows that in primary granulosa cells from prepubertal rat ovary, StAR transcript and protein are acutely induced by gonadotropin (FSH). To determine the sequence elements required for hormone inducibility of the StAR promoter, truncated regions of the -1002/+6 sequence of the mouse gene were ligated to pCAT-Basic plasmid and transfected by electropotation to freshly prepared cells. FSH inducibility determined over a 6-h incubation was 10-40-fold above basal levels of chloramphenicol acetyltransferase activity. These functional studies, supported by electrophoretic mobility shift assays indicated that two sites were sufficient for transcription of the StAR promoter constructs: a non-consensus binding sequence (-81/-72) for CCAAT enhancer-binding protein β (C/EBPβ) and a consensus motif for GATA-4 binding (-61/-66). Western analyses showed that GATA-4 is constitutively expressed in the granulosa cells, while all isoforms of C/EBPβ were markedly inducible by FSH. Site-directed mutations of both binding sequences practically ablated both basal and hormone-driven chloramphenicol acetyltransferase activities to less than 5% of the parental -96/+6 construct. Unlike earlier notions, elimination of potential binding sites for steroidogenic factor-1, a well known tissue-specific transcription factor, did not impair StAR transcription. Consequently, we propose that C/EBPβ and GATA-4 represent a novel combination of transcription factors capable of conferring an acute response to hormones upon their concomitant binding to the StAR promoter.

Original languageEnglish
Pages (from-to)17987-17996
Number of pages10
JournalJournal of Biological Chemistry
Volume274
Issue number25
DOIs
StatePublished - 18 Jun 1999

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