PGC-1 functions as a transcriptional coactivator for the retinoid X receptors.
Ligand-dependent gene transcription mediated by the nuclear receptors involves the recruitment of transcriptional coactivators to the ligand-binding domain (LBD), which leads to interaction with the basal transcription machinery, and ultimately with RNA polymerase II. Although most of these coactivators are ubiquitously expressed, a tissue-selective coactivator, PGC-1, has recently been characterized. Because PGC-1 and the retinoid X receptors (RXRs) possess an overlapping tissue distribution, we investigated whether PGC-1 is a coactivator for the retinoid X receptors. In a transient transfection assay, PGC-1 augments ligand-stimulated RXR transcription. Furthermore, PGC-1 efficiently enhances the RXR element-driven reporter gene transcription by all three RXR isoforms. An immunoprecipitation assay reveals that PGC-1 and RXRalpha interact in vivo. In addition, a glutathione S-transferase pull-down assay showed that this interaction requires the presence of the LXXLL motif of PGC-1. We demonstrate further, in a mammalian two-hybrid assay, that this physical interaction also requires the presence of the AF-2 region of RXR to interact with the LXXLL motif of PGC-1, which is consistent with our protein-protein interaction results. A time-resolved fluorescence assay shows that a peptide within the NR box of PGC-1 is efficiently recruited by a ligand-bound RXRalpha in vitro. Finally, PGC-1 and TIF2 synergistically enhance ligand-activated RXRalpha transcriptional activity. Taken together, these results indicate that PGC-1 is a bona fide coactivator for RXRalpha.
Delerive
Philippe
P
Department of Gene Regulation, Bone, and Inflammation Research, Eli Lilly Research Laboratories, Lilly Corporate Center, Indianapolis, Indiana 46285, USA. delerive_philippe@lilly.com
Wu
Yifei
Y
Burris
Thomas P
TP
Chin
William W
WW
Suen
Chen S
CS
D002460:Cell Line; D006801:Humans; D051958:Nuclear Receptor Coactivator 2; D011485:Protein Binding; D018168:Receptors, Retinoic Acid / Q000235:genetics*; D047488:Retinoid X Receptors; D015534:Trans-Activators / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics* / Q000502:physiology*
C498001:NCOA2 protein, human; D051958:Nuclear Receptor Coactivator 2; D018168:Receptors, Retinoic Acid; D047488:Retinoid X Receptors; D015534:Trans-Activators; D014157:Transcription Factors; C111264:peroxisome-proliferator-activated receptor-gamma coactivator-1