The transcriptional coactivator DRIP/mediator complex is involved in vitamin D receptor function and regulates keratinocyte proliferation and differentiation.
Mediator is a multisubunit coactivator complex that facilitates transcription of nuclear receptors. We investigated the role of the mediator complex as a coactivator for vitamin D receptor (VDR) in keratinocytes. Using VDR affinity beads, the vitamin D receptor interacting protein (DRIP)/mediator complex was purified from primary keratinocytes, and its subunit composition was determined by mass spectrometry. The complex included core subunits, such as DRIP205/MED1 (MED1), that directly binds to VDR. Additional subunits were identified that are components of the RNA polymerase II complex. The functions of different mediator components were investigated by silencing its subunits. The core subunit MED1 facilitates VDR activity and regulating keratinocyte proliferation and differentiation. A newly described subunit MED21 also has a role in promoting keratinocyte proliferation and differentiation, whereas MED10 has an inhibitory role. Blocking MED1/MED21 expression caused hyperproliferation of keratinocytes, accompanied by increases in mRNA expression of the cell cycle regulator cyclin D1 and/or glioma-associated oncogene homolog. Blocking MED1 or MED21 expression also resulted in defects in calcium-induced keratinocyte differentiation, as indicated by decreased expression of differentiation markers and decreased translocation of E-cadherin to the membrane. These results show that keratinocytes use the transcriptional coactivator mediator to regulate VDR functions and control keratinocyte proliferation and differentiation.
Oda
Yuko
Y
Department of Medicine and Endocrinology, University of California, San Francisco and Veterans Affairs Medical Center San Francisco, San Francisco, California 94121, USA. yuko.oda@ucsf.edu
Chalkley
Robert J
RJ
Burlingame
Alma L
AL
Bikle
Daniel D
DD
D015820:Cadherins / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D019938:Cyclin D1 / Q000378:metabolism; D006801:Humans; D015603:Keratinocytes / Q000166:cytology* / Q000502:physiology*; D056892:Mediator Complex / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D056913:Mediator Complex Subunit 1 / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D012319:RNA Polymerase II / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering; D018167:Receptors, Calcitriol / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism*; D014158:Transcription, Genetic / Q000502:physiology
C530104:CCND1 protein, human; D015820:Cadherins; C113182:DRIP, VDR interacting protein complex; C538855:MED1 protein, human; C538711:MED10 protein, human; C098617:MED21 protein, human; C538714:MED31 protein, human; D056892:Mediator Complex; D056913:Mediator Complex Subunit 1; D009687:Nuclear Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D018167:Receptors, Calcitriol; D018160:Receptors, Cytoplasmic and Nuclear; D015534:Trans-Activators; D019938:Cyclin D1; D012319:RNA Polymerase II; D002118:Calcium