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形成中的协同作用。我们实验室的研究表明，MyoD在未分化成肌细胞中的活性是通过其与1类组蛋白去乙酰化酶（HDAC）或组蛋白乙酰转移酶（HAT）的关联来控制的。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，肌肉特异性基因保持在抑制状态，直到诱导成肌细胞分化。我们的目的是探索MyoD的这一新功能，并在未分化和分化的肌肉细胞中分别在肌肉特异性基因的启动子上鉴定与MyoD特异性相互作用的hdac和HATs。还提出了实验来确定这两种酶是否通过包括其他染色质重塑因子（例如，甲基化酶，HP1和SWl/SNF）的电路与MyoD一起起作用。在Aim 1中，我们计划在染色质修饰因子的帮助下，研究MyoD是否在肌肉分化之前抑制肌肉特异性基因中起一般作用。还提出了确定MyoD是否招募HDAC以影响染色质结构（特别是组蛋白的“标记”）的启动子的实验。在Aim 2中，我们计划探索一旦发生分化，MyoD是否会与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募集是否依赖于MyoD。我们还计划研究MyoD是否与HATs进行交叉对话，以在肌肉特异性基因的启动子内建立组蛋白乙酰化模式，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存在功能联系，以调节MyoD在分化时激活MyoD应答基因的能力。

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.