Regulation of rat cytochrome P450C24 (CYP24) gene expression. Evidence for functional cooperation of Ras-activated Ets transcription factors with the vitamin D receptor in 1,25-dihydroxyvitamin D(3)-mediated induction.
Transcription of the rat CYP24 gene is induced by 1, 25-dihydroxyvitamin D(3) (1,25-(OH)(2)D(3)) through two vitamin D response elements (VDREs). A functional Ras-dependent Ets-binding site (EBS) was located downstream from the proximal VDRE and was critical to 1,25(OH)(2)D(3)-mediated induction. Cotransfection of Ets-1 and Ets-2 stimulated induction, which was lost when the EBS was mutated. Multiple nuclear-protein complexes from COS-1 cells bound to the EBS in which three complexes were immunologically related to Ets-1. Transcriptional synergy was observed between the proximal VDRE and adjacent EBS as was the attendant formation of a ternary complex between vitamin D receptor- retinoid X receptor (VDR. RXR) and Ets-1. In the absence of 1,25-(OH)(2)D(3) or in the presence of an inactive proximal VDRE, the EBS failed to respond to exogenous Ets-1. However, Ets-1 increased basal expression when cotransfected with a mutant VDR. The inductive action of 1, 25-(OH)(2)D(3) was substantially increased by Ras, which was ablated by mutagenesis of the EBS or by expression of a mutated Ets-1 protein (T38A). EBS contribution to hormone induction was prevented by manumycin A, an inhibitor of Ras farnesylation. A fundamental role was established for transcriptional cooperation between Ras-activated Ets proteins and the VDR.RXR complex in mediating 1, 25-(OH)(2)D(3) action on the CYP24 promoter.
Dwivedi
P P
PP
Department of Biochemistry, University of Adelaide, Adelaide, South Australia 5005, Australia.
Omdahl
J L
JL
Kola
I
I
Hume
D A
DA
May
B K
BK
D000818:Animals; D001665:Binding Sites; D002117:Calcitriol / Q000494:pharmacology*; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis / Q000235:genetics*; D019281:Dimerization; D015971:Gene Expression Regulation, Enzymologic; D009687:Nuclear Proteins / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D050784:Proto-Oncogene Protein c-ets-1; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D050783:Proto-Oncogene Proteins c-ets; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D051381:Rats; D018167:Receptors, Calcitriol / Q000378:metabolism*; D018168:Receptors, Retinoic Acid / Q000378:metabolism; D020218:Response Elements; D047488:Retinoid X Receptors; D013250:Steroid Hydroxylases / Q000096:biosynthesis / Q000235:genetics*; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D065668:Vitamin D3 24-Hydroxylase; D018631:ras Proteins / Q000378:metabolism*
C494043:Ets1 protein, rat; D009687:Nuclear Proteins; D050784:Proto-Oncogene Protein c-ets-1; D011518:Proto-Oncogene Proteins; D050783:Proto-Oncogene Proteins c-ets; D018167:Receptors, Calcitriol; D018168:Receptors, Retinoic Acid; D047488:Retinoid X Receptors; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D065668:Vitamin D3 24-Hydroxylase; D019908:Proto-Oncogene Proteins c-raf; D018631:ras Proteins; D002117:Calcitriol