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.
Laboratory of Biochemistry and Molecular Biology, The Rockefeller University, New York, NY 10021, USA.
Wei
W
Chen
Qiheng
Q
Yang
Robert G
RG
Roeder
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