Department of Biochemistry and Molecular Biology and Simmons Cancer Institute, Southern Illinois University School of Medicine, Carbondale, IL, United States of America.
Molecular Pathology Unit, Massachusetts General Hospital Research Institute, Charlestown, MA, United States of America.
PLoS One. 2021 Jan 19;16(1):e0245618. doi: 10.1371/journal.pone.0245618. eCollection 2021.
Skeletal muscle gene expression is governed by the myogenic regulatory family (MRF) which includes MyoD (MYOD1) and myogenin (MYOG). MYOD1 and MYOG are known to regulate an overlapping set of muscle genes, but MYOD1 cannot compensate for the absence of MYOG in vivo. In vitro, late muscle genes have been shown to be bound by both factors, but require MYOG for activation. The molecular basis for this requirement was unclear. We show here that MYOG is required for the recruitment of TBP and RNAPII to muscle gene promoters, indicating that MYOG is essential in assembling the transcription machinery. Genes regulated by MYOD1 and MYOG include genes required for muscle fusion, myomaker and myomerger, and we show that myomaker is fully dependent on activation by MYOG. We also sought to determine the role of MYOD1 in MYOG dependent gene activation and unexpectedly found that MYOG is required to maintain Myod1 expression. However, we also found that exogenous MYOD1 was unable to compensate for the loss of Myog and activate muscle gene expression. Thus, our results show that MYOD1 and MYOG act in a feed forward loop to maintain each other's expression and also show that it is MYOG, and not MYOD1, that is required to load TBP and activate gene expression on late muscle gene promoters bound by both factors.
骨骼肌基因表达受肌源性调节因子家族（MRF）调控，该家族包括 MyoD（MYOD1）和肌生成素（MYOG）。已知 MYOD1 和 MYOG 调节一组重叠的肌肉基因，但 MYOD1 不能在体内补偿 MYOG 的缺失。在体外，已经表明晚期肌肉基因被这两种因子结合，但需要 MYOG 才能激活。这一需求的分子基础尚不清楚。我们在这里表明，MYOG 是招募 TBP 和 RNAPII 到肌肉基因启动子所必需的，这表明 MYOG 对于组装转录机制是必不可少的。MYOD1 和 MYOG 调节的基因包括肌肉融合所需的基因、肌原和肌联，我们表明肌原完全依赖于 MYOG 的激活。我们还试图确定 MYOD1 在 MYOG 依赖的基因激活中的作用，出乎意料的是，我们发现 MYOG 是维持 Myod1 表达所必需的。然而，我们还发现，外源性 MYOD1 无法补偿 Myog 的缺失并激活肌肉基因表达。因此，我们的结果表明，MYOD1 和 MYOG 以正反馈回路相互作用，维持彼此的表达，并且表明正是 MYOG，而不是 MYOD1，需要加载 TBP 并激活两种因子结合的晚期肌肉基因启动子上的基因表达。
