Dynamic interactions and cooperative functions of PGC-1alpha and MED1 in TRalpha-mediated activation of the brown-fat-specific UCP-1 gene.
PGC-1alpha is an inducible nuclear receptor coactivator with direct functions in both p300-mediated chromatin remodeling and Mediator-dependent transcription in vitro. Here, we have employed the PPARgamma- and TRalpha-activated brown adipose tissue-specific UCP-1 enhancer to investigate mechanistic aspects of PGC-1alpha function. We first demonstrate a cellular role for the PGC-1alpha-interacting MED1 subunit of Mediator in UCP-1 induction, as well as the accumulation of TRalpha, PPARgamma, PGC-1alpha, and MED1 on the UCP-1 enhancer in brown adipocytes. We then use biochemical assays to show that (i) PGC-1alpha is recruited to the TRalpha-RXRalpha-UCP-1 enhancer complex through interaction of an N-terminal LXXLL domain with TRalpha, (ii) MED1/Mediator displaces PGC-1alpha from TRalpha through LXXLL domain competition, and (iii) upon loss of PGC-1alpha-TRalpha interactions, PGC-1alpha remains associated with the enhancer complex through an interaction between PGC-1alpha and MED1 C-terminal domains. These results indicate dynamic MED1-dependent PGC-1alpha interactions related to functions in both chromatin remodeling and the transition to subsequent transcription initiation.
Chen
Wei
W
Laboratory of Biochemistry and Molecular Biology, The Rockefeller University, New York, NY 10021, USA.
Yang
Qiheng
Q
Roeder
Robert G
RG
D002001:Adipose Tissue, Brown / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002478:Cells, Cultured; D042002:Chromatin Assembly and Disassembly; D004742:Enhancer Elements, Genetic; D007473:Ion Channels / Q000235:genetics / Q000378:metabolism*; D008024:Ligands; D056913:Mediator Complex Subunit 1; D051379:Mice; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D047495:PPAR gamma / Q000378:metabolism; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D047490:Retinoid X Receptor alpha / Q000378:metabolism; D037021:Thyroid Hormone Receptors alpha / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection; D000071256:Uncoupling Protein 1; D015854:Up-Regulation
D007473:Ion Channels; D008024:Ligands; C538856:Med1 protein, mouse; D056913:Mediator Complex Subunit 1; D024101:Mitochondrial Proteins; D047495:PPAR gamma; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; C485290:Ppargc1a protein, mouse; D012333:RNA, Messenger; D047490:Retinoid X Receptor alpha; D037021:Thyroid Hormone Receptors alpha; D015534:Trans-Activators; D014157:Transcription Factors; C000604372:Ucp1 protein, mouse; D000071256:Uncoupling Protein 1