P/CAF rescues the Bhlhe40-mediated repression of MyoD transactivation.
Previously, we found that MRFs (myogenic regulatory factors) regulated the expression of PGC-1alpha (peroxisome-proliferator-activated receptor gamma co-activator 1alpha) by targeting a short region, from nt -49 to +2 adjacent to the transcription initiation site, that contained two E-boxes. However, only the E2-box had significant affinity for MRFs, and the E1-box was predicted to be the target of Bhlhe40 (basic helix-loop-helix family, member e40, also known as Stra13, Bhlhb2, DEC1 and Sharp2), a transcriptional repressor implicated in the regulation of several physiological processes. In the present study, by using EMSA (electrophoresis mobility-shift assay), we confirmed that Bhlhe40 targeted the E1-box and formed a complex with the basic helix-loop-helix transcription factor MyoD (myogenic differentiation factor D) on the PGC-1alpha core promoter. We demonstrate that Bhlhe40 binds to the promoters of PGC-1alpha and myogenic genes in vivo and that Bhlhe40 represses the MyoD-mediated transactivation of these promoters. Furthermore, we found that this repression could be relieved by P/CAF (p300/CBP-associated factor) in a dose-dependent manner, but not by CBP [CREB (cAMP-response-element-binding protein)-binding protein]. Bhlhe40 interacted with P/CAF and this interaction disrupted the interaction between P/CAF and MyoD. These results suggest that Bhlhe40 functions as a repressor of MyoD by binding to adjacent E-boxes and sequestering P/CAF from MyoD.
Hsiao
Sheng P
SP
Department of Life Sciences, National Central University, 300 Jhongda Road, Jhongli 32054, Taiwan.
Huang
Kai M
KM
Chang
Hsin Y
HY
Chen
Shen L
SL
D000818:Animals; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / Q000502:physiology*; D002460:Cell Line; D051379:Mice; D017570:MyoD Protein / Q000037:antagonists & inhibitors* / Q000235:genetics*; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D013489:Suppression, Genetic; D015534:Trans-Activators / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics; D014157:Transcription Factors; D015533:Transcriptional Activation / Q000502:physiology*; D050880:p300-CBP Transcription Factors / Q000502:physiology*
D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D017570:MyoD Protein; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; C485290:Ppargc1a protein, mouse; D015534:Trans-Activators; D014157:Transcription Factors; D050880:p300-CBP Transcription Factors