title: Two distinct coactivators, DRIP/mediator and SRC/p160, are differentially involved in vitamin D receptor transactivation during keratinocyte differentiation.
abstract: Cell programs such as proliferation and differentiation involve the sequential activation and repression of gene expression. Vitamin D, via its active metabolite 1,25-dihydroxyvitamin D [1,25-(OH)2D3)], controls the proliferation and differentiation of a number of cell types, including keratinocytes, by directly regulating transcription. Two classes of coactivators, the vitamin D receptor (VDR)-interacting proteins (DRIP/mediator) and the p160 steroid receptor coactivator family (SRC/p160), control the actions of nuclear hormone receptors, including the VDR. However, the relationship between these two classes of coactivators is not clear. Using glutathione-S-transferase-VDR affinity beads, we have identified the DRIP/mediator complex as the major VDR binding complex in proliferating keratinocytes. After the cells differentiated, members of the SRC/p160 family were identified in the complex but not major DRIP subunits. Both DRIP and SRC proteins were expressed in keratinocytes. DRIP205 expression decreased during differentiation, although SRC-3 levels increased. Both DRIP205 and SRC-3 potentiated vitamin D-induced transcription in proliferating cells, but during differentiation, DRIP205 was no longer effective. These results indicate that these two distinct coactivators are sequentially involved in vitamin D regulation of gene transcription during keratinocyte differentiation, suggesting that these coactivators are part of the means by which the temporal sequence of gene expression is regulated during the differentiation process.
authors.affiliation: Departments of Medicine and Endocrinology University of California San Francisco and Veterans Affairs Medical Center, San Francisco, California 94121, USA. y2073@itsa.ucsf.edu.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Oda
authors.forename: Carina
authors.initials: C
authors.lastname: Sihlbom
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Chalkley
authors.forename: Lan
authors.initials: L
authors.lastname: Huang
authors.forename: Christophe
authors.initials: C
authors.lastname: Rachez
authors.forename: Chao-Pei Betty
authors.initials: CP
authors.lastname: Chang
authors.forename: Alma L
authors.initials: AL
authors.lastname: Burlingame
authors.forename: Leonard P
authors.initials: LP
authors.lastname: Freedman
authors.forename: Daniel D
authors.initials: DD
authors.lastname: Bikle
mesh_terms: D000595:Amino Acid Sequence; D002454:Cell Differentiation / Q000187:drug effects; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D051548:Histone Acetyltransferases; D006801:Humans; D007231:Infant, Newborn; D015603:Keratinocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D013058:Mass Spectrometry; D056892:Mediator Complex; D056913:Mediator Complex Subunit 1; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009687:Nuclear Proteins / Q000378:metabolism*; D056920:Nuclear Receptor Coactivator 1; D011485:Protein Binding; D018167:Receptors, Calcitriol / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation / Q000187:drug effects; D014807:Vitamin D / Q000494:pharmacology
chemical_list: C113182:DRIP, VDR interacting protein complex; C538855:MED1 protein, human; C491863:MED4 protein, human; D056892:Mediator Complex; D056913:Mediator Complex Subunit 1; D009687:Nuclear Proteins; D018167:Receptors, Calcitriol; D015534:Trans-Activators; D014157:Transcription Factors; D014807:Vitamin D; D051548:Histone Acetyltransferases; C538859:NCOA1 protein, human; D056920:Nuclear Receptor Coactivator 1