Chen Wei, Yang Qiheng, Roeder Robert G
Laboratory of Biochemistry and Molecular Biology, The Rockefeller University, New York, NY 10021, USA.
Mol Cell. 2009 Sep 24;35(6):755-68. doi: 10.1016/j.molcel.2009.09.015.
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.
PGC-1α是一种可诱导的核受体辅激活因子，在体外对p300介导的染色质重塑和中介体依赖性转录均具有直接作用。在此，我们利用PPARγ和TRα激活的棕色脂肪组织特异性UCP-1增强子来研究PGC-1α功能的机制方面。我们首先证明了中介体中与PGC-1α相互作用的MED1亚基在UCP-1诱导中的细胞作用，以及TRα、PPARγ、PGC-1α和MED1在棕色脂肪细胞的UCP-1增强子上的积累。然后我们使用生化分析表明：（i）PGC-1α通过其N端LXXLL结构域与TRα的相互作用被招募到TRα-RXRα-UCP-1增强子复合物中；（ii）MED1/中介体通过LXXLL结构域竞争将PGC-1α从TRα上置换下来；（iii）当PGC-1α与TRα的相互作用丧失时，PGC-1α通过PGC-1α与MED1 C端结构域之间的相互作用仍与增强子复合物结合。这些结果表明了与染色质重塑和向后续转录起始转变功能相关的动态MED1依赖性PGC-1α相互作用。
