Interplay between MyoD and chromatin-modifying enzymes

描述(由申请人提供)：我们的长期目标是了解MyoD和染色质修饰因子在控制骨骼肌发生中的协同作用。我们实验室的工作表明，MyoD在未分化的成肌细胞中的活性是通过其与组蛋白1脱乙酰酶(HDAC)的结合或在分化发生时受组蛋白乙酰转移酶(HAT)控制的。我们的新研究表明，MyoD和HDAC1在染色质上的相互作用现在可能定义了一种新的机制，通过这种机制，肌肉特异基因一直处于抑制状态，直到成肌细胞被诱导分化。我们的目的是探索MyoD的这一新功能，并进行研究，以确定在未分化和已分化的肌肉细胞中，分别在肌肉特异性基因的启动子上与MyoD特异性相互作用的HDAC和HATS。还建议进行实验，以确定这两种酶是否通过包括其他染色质重塑因子(如甲基酶、HP1和SWL/SNF)的电路与MyoD一起发挥作用。在目标1中，我们计划研究MyoD是否在肌肉分化之前，以及在染色质修饰因子的帮助下，在抑制肌肉特异基因方面发挥普遍作用。还提出了一些实验，以确定MyoD是否正在招募HDAC来影响染色质结构，特别是组蛋白的‘标记’。在目标2中，我们计划探索一旦分化发生，MyoD是否与P/Caf和/或p300/CBP一起占据肌肉基因的启动子，如果是，则进行研究以确定它们的招募是否依赖MyoD。我们还计划调查MyoD是否与HATS交叉对话，以建立肌肉特异基因启动子内的组蛋白乙酰化模式，如果是，则进行动力学研究，以确定这是否与它们的表达相关。最后，我们计划确定磷酸化和乙酰化之间是否在调节MyoD在分化时激活MyoD反应基因的能力方面存在功能联系。

DESCRIPTION (provided by applicant): Our long-term goal is to understand the synergism between MyoD and chromatin-modifying factors in the control of skeletal myogenesis. Work from our laboratory has revealed that MyoD's activities in undifferentiated myoblasts are controlled through its association with a class 1 histone deacetylase (HDAC), or by a histone acetyltransferase (HAT) as differentiation occurs. Our new studies indicate that the interaction between MyoD and HDAC1 on chromatin may now define a new mechanism by which musclespecific genes are kept in a repressed state until myoblasts are induced to differentiate. Our purpose is to explore this new function of MyoD, and in addition, pursue studies that identify the HDACs and HATs that specifically interact with MyoD at the promoters of muscle-specific genes in undifferentiated and differentiated muscle cells, respectively. Experiments are also proposed to determine whether these two enzymes are functioning with MyoD through a circuitry that include other chromatin remodeling factors (e.g., methylases, HP1, and SWl/SNF). In Aim 1, we plan to investigate whether MyoD is serving a general role in repressing muscle-specific genes prior to muscle differentiation, and with the help of chromatin modifying factors. Experiments to determine whether MyoD is recruiting an HDAC to promoters for affecting chromatin structure, specifically the 'markings' of histones, are also proposed. In Aim 2, we plan to explore whether MyoD is occupying the promoters of muscle genes along with P/CAF and/or p300/CBP once differentiation occurs, and if so, perform studies to determine whether their recruitment depends on MyoD. We also plan to investigate whether MyoD cross talks with HATs to establish a pattern of histone acetylation within the promoters of muscle-specific genes, and if so, conduct kinectic studies to determine whether this correlates to their expression. Finally, we plan to determine whether there is a functional link between phosphorylation and acetylation in regulating MyoD's ability to activate MyoD-responsive genes upon differentiation.