REGULATION OF MYOD POST TRANSCRIPTIONAL MODIFICATIONS

本研究的目的是了解的分子和细胞机制，调节肌原性bHLH蛋白的转录活性。更具体地说，我们感兴趣的是研究开关，使MyoD成为转录活性一旦未分化的成肌细胞过渡到分化的肌管。MyoD活性是卫星细胞增殖所必需的，并且在横纹肌肉瘤（一种儿科实体瘤）中失调。 骨骼肌细胞再生和肿瘤转化的分子机制仍不清楚。乙酰化是一个动态过程，涉及乙酰转移酶和脱乙酰酶的作用。MyoD是p300和PCAF乙酰化的直接靶标。尽管如此，乙酰化介导的PCAF，而不是由p300，需要协助MyoD依赖的转录和肌肉分化。PCAF介导的MyoD乙酰化导致DNA结合能力增加，并改变MyoD与DNA结合的构象。我们以前分析了p300和PCAF乙酰转移酶对肌肉分化的贡献。 我们建议继续这一调查。具体目标是：1.研究HDAC是否与MyoD物理相关并阻碍肌肉分化。2.分析MyoD、pRb和HDAC1在调节肌肉特异性转录中的相互作用.探讨乙酰化在骨骼肌细胞再生和肿瘤转化中的作用。在过去的一年中，我们已经开始表征含有MyoD和HDAC1的细胞复合物的组成，并启动了肌肉细胞中HDAC1过表达的实验。我们的初步结果表明，HDAC 1的强制表达拮抗了MyoD依赖性转录并抑制了肌肉分化。

The present study is aimed at the understanding of the molecular and cellular mechanisms that regulate the transcriptional activity of the myogenic bHLH proteins. More specifically, we are interested in studying the switches that allow MyoD to become transcriptionally active once undifferentiated myoblasts transition into differentiated myotubes. MyoD activity is required for proliferation of satellite cells and is deregulated in rhabdomyosarcoma, a pediatric solid tumor. The molecular mechanisms of regeneration and neoplastic transformation of skeltal muscle cells remian unclear. Acetylation is a dynamic process involving the actions of both acetyltransferases and deacetylases. MyoD is a direct target of acetylation by both p300 and PCAF. Nonetheless, acetylation mediated by PCAF, but not by p300, is required to assist MyoD-dependent transcription and muscle differentiation. PCAF-mediated acetylation of MyoD results in an increased DNA binding capability and modify the conformation of MyoD bound to DNA. We have previously analyzed the contribution of the p300 and PCAF acetyltransferases to muscle differentiation. We propose to continue this line of investigation. The specific aims are:1. To investigate whether the HDACs physically associate with MyoD and impede muscle differentiation. 2. To analyze the functional interplay of MyoD, pRb and HDAC1 in regulating muscle specific transcription.3. To investigate the role of acetylation in both regeneration and neoplastic transformation of skeletal muscle cells. In the past year, we have begun characterizing the composition of a cellular complex containing MyoD and HDAC1 and have initiated experiments of HDAC1 overexpression in muscle cells. Our preliminary results indicate that forced expression of HDAC1 antagonizes MyoD-dependent transcription and prohibits muscle differentiation.