Conditional response of the human steroidogenic acute regulatory protein gene promoter to sterol regulatory element binding protein-1a.
The steroidogenic acute regulatory protein (StAR) gene controls the rate-limiting step in the biogenesis of steroid hormones, delivery of cholesterol to the cholesterol side-chain cleavage enzyme on the inner mitochondrial membrane. We determined whether the human StAR promoter is responsive to sterol regulatory element-binding proteins (SREBPs). Expression of SREBP-1a stimulated StAR promoter activity in the context of COS-1 cells and human granulosa-lutein cells. In contrast, expression of SREBP-2 produced only a modest stimulation of StAR promoter activity. One of the SREBP-1a response elements in the StAR promoter was mapped in deletion constructs and by site-directed mutagenesis between nucleotides -81 to -70 from the transcription start site. This motif bound recombinant SREBPs in electrophoretic mobility shift assays, but with lesser affinity than a low density lipoprotein receptor SREBP-binding site. An additional binding site for the transcriptional modulator, yin yang 1 (YY1), was observed within the SREBP-binding site (nucleotides -73 to -70). Mutation of the YY1-binding site increased the responsiveness of the StAR promoter to exogenous SREBP-1a, but did not alter the affinity for SREBP-1a binding in electrophoretic mobility gel shift assays. Manipulations that altered endogenous mature SREBP-1a levels (e.g. culture in lipoprotein-deficient medium and addition of 27-hydroxycholesterol) did not affect StAR promoter function, but influenced low density lipoprotein receptor promoter activity. We conclude that 1) the human StAR promoter is conditionally responsive to SREBP-1a such that promoter activity is up-regulated in the presence of high levels of SREBP-1a, but is unaffected when mature SREBP levels are suppressed; and 2) the human StAR promoter is selectively responsive to SREBP-1a.
Christenson
L K
LK
Center for Research on Reproduction and Women's Health, University of Pennsylvania (L.K.C., J.F.S.), Philadelphia, Pennsylvania 19104.
Osborne
T F
TF
McAllister
J M
JM
Strauss
J F
JF
D000818:Animals; D001483:Base Sequence; D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D019556:COS Cells; D002417:Cattle; D002522:Chlorocebus aethiops; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006107:Granulosa Cells / Q000378:metabolism; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010750:Phosphoproteins / Q000235:genetics*; D011401:Promoter Regions, Genetic; D051381:Rats; D011973:Receptors, LDL / Q000235:genetics; D011994:Recombinant Proteins / Q000378:metabolism; D016415:Sequence Alignment; D017384:Sequence Deletion; D012689:Sequence Homology, Nucleic Acid; D051780:Sterol Regulatory Element Binding Protein 1; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection; D000098682:Steroidogenic Acute Regulatory Protein
D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D008565:Membrane Proteins; D010750:Phosphoproteins; D011973:Receptors, LDL; D011994:Recombinant Proteins; C497387:SREBF1 protein, human; C497388:Srebf1 protein, mouse; C497389:Srebf1 protein, rat; D051780:Sterol Regulatory Element Binding Protein 1; D014157:Transcription Factors; D000098682:Steroidogenic Acute Regulatory Protein