Division of Transcriptomics, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-0054, Japan.
Department of Cellular Biochemistry, Graduate School of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-0054, Japan.
J Biochem. 2021 Sep 7;169(6):653-661. doi: 10.1093/jb/mvab001.
MyoD, a myogenic differentiation protein, has been studied for its critical role in skeletal muscle differentiation. MyoD-expressing myoblasts have a potency to be differentiated with proliferation of ectopic cells. However, little is known about the effect on chromatin structure of MyoD binding in proliferative myoblasts. In this study, we evaluated the chromatin structure around MyoD-bound genome regions during the cell cycle by chromatin immunoprecipitation sequencing. Genome-wide analysis of histone modifications was performed in proliferative mouse C2C12 myoblasts during three phases (G1, S, G2/M) of the cell cycle. We found that MyoD-bound genome regions had elevated levels of active histone modifications, such as H3K4me1/2/3 and H3K27ac, compared with MyoD-unbound genome regions during the cell cycle. We also demonstrated that the elevated H3K4me2/3 modification level was maintained during the cell cycle, whereas the H3K27ac and H3K4me1 modification levels decreased to the same level as MyoD-unbound genome regions during the later phases. Immunoblot analysis revealed that MyoD abundance was high in the G1 phase then decreased in the S and G2/M phases. Our results suggest that MyoD binding formed selective epigenetic memories with H3K4me2/3 during the cell cycle in addition to myogenic gene induction via active chromatin formation coupled with transcription.
肌节同源蛋白 1（MyoD）作为一种肌生成分化蛋白，其在骨骼肌分化中的关键作用已有研究。MyoD 表达的成肌细胞具有增殖异位细胞的潜力，进而分化。然而，MyoD 结合对增殖性成肌细胞染色质结构的影响知之甚少。在这项研究中，我们通过染色质免疫沉淀测序评估了细胞周期中 MyoD 结合基因组区域周围的染色质结构。在细胞周期的三个阶段（G1、S、G2/M）中，我们在增殖性小鼠 C2C12 成肌细胞中进行了全基因组组蛋白修饰分析。与细胞周期中的 MyoD 未结合基因组区域相比，我们发现 MyoD 结合的基因组区域具有更高水平的活性组蛋白修饰，如 H3K4me1/2/3 和 H3K27ac。我们还证明，H3K4me2/3 修饰水平在细胞周期中保持升高，而 H3K27ac 和 H3K4me1 修饰水平在后期阶段降低至与 MyoD 未结合基因组区域相同的水平。免疫印迹分析显示，MyoD 在 G1 期大量存在，然后在 S 和 G2/M 期减少。我们的结果表明，MyoD 结合在细胞周期中形成了与 H3K4me2/3 选择性的表观遗传记忆，除了通过与转录偶联的活性染色质形成诱导肌生成基因外。
