Regulation of steroidogenic acute regulatory protein transcription in largemouth bass by orphan nuclear receptor signaling pathways.
The steroidogenic acute regulatory (StAR) protein mediates the rate-limiting step of mitochondrial transport of cholesterol for steroid biosynthesis. To investigate the regulation of this protein in lower vertebrates, we cloned the StAR coding region from large-mouth bass for analysis. Induction of the mRNA corresponded with increasing levels of plasma sex steroids in vivo. Cultures of largemouth bass ovarian follicles were exposed to dibutyryl cAMP (dbcAMP), a potent signaling molecule for steroidogenesis. StAR mRNA expression was significantly up-regulated by dbcAMP signaling, suggesting that the 5' regulatory region of the gene is functionally conserved. To further analyze its transcriptional regulation, a 2.9-kb portion of the promoter was cloned and transfected into Y-1 cells, a steroidogenic mouse adrenocortical cell line. The promoter activity was induced in a dose-responsive manner upon stimulation with dbcAMP; however, deletion of 1 kb from the 5' end of the promoter segment significantly diminished the transcriptional activation. A putative retinoic acid-related receptor-alpha/rev-erb alpha element was identified between the -1.86- and -2.9-kb region and mutated to assess its potential role in dbcAMP regulation of the promoter. Mutation of the rev-erb alpha element significantly impeded dbcAMP-induced activation. Chromatin immunoprecipitation and EMSA results revealed rev-erb alpha and retinoic acid-related receptor-alpha enrichment at the site under basal and dbcAMP-induced conditions, respectively. These results implicate important roles for these proteins previously uncharacterized for the StAR promoter. Altogether these data suggest novel regulatory mechanisms for dbcAMP up-regulation of StAR transcription in the distal part of the largemouth bass promoter.
Kocerha
Jannet
J
Department of Biochemistry and Molecular Biology, University of Florida, P.O. Box 110885, Gainesville, Florida 32611, USA.
Prucha
Melinda S
MS
Kroll
Kevin J
KJ
Steinhilber
Dieter
D
Denslow
Nancy
N
D000818:Animals; D001492:Bass / Q000235:genetics* / Q000378:metabolism; D002478:Cells, Cultured; D003001:Cloning, Molecular; D005260:Female; D005786:Gene Expression Regulation; D051379:Mice; D056953:Nuclear Receptor Subfamily 1, Group D, Member 1 / Q000378:metabolism / Q000502:physiology; D057094:Nuclear Receptor Subfamily 1, Group F, Member 1 / Q000378:metabolism / Q000502:physiology; D057093:Orphan Nuclear Receptors / Q000378:metabolism / Q000502:physiology*; D010750:Phosphoproteins / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D015398:Signal Transduction / Q000235:genetics; D014158:Transcription, Genetic; D014162:Transfection; D000098682:Steroidogenic Acute Regulatory Protein
D056953:Nuclear Receptor Subfamily 1, Group D, Member 1; D057094:Nuclear Receptor Subfamily 1, Group F, Member 1; D057093:Orphan Nuclear Receptors; D010750:Phosphoproteins; D000098682:Steroidogenic Acute Regulatory Protein