Transcription Factor Function in Chromatin

描述（由申请人提供）：为了理解正常发育和分化，有必要确定细胞启动新的基因表达程序并促进特定细胞谱系形成的机制。通常，这涉及转录沉默的基因的激活，这些基因可能被整合到抑制性染色质结构中。证据支持这样的想法，即分化特异性转录调节因子和重塑或改变染色质结构的酶合作，使基因组DNA更容易进入转录机制。SWI/SNF酶以ATP依赖性方式重塑核小体结构，并促进体外和体内转录因子功能。这些酶的成分是胚胎发育所必需的，有些还起到肿瘤抑制剂的作用。此外，SWI/SNF酶与其他已知的肿瘤抑制剂相互作用，并参与细胞周期控制。因此，这些酶是正常细胞功能以及分化和发育所广泛需要的，并且它们的失调与肿瘤形成有关。 骨骼肌分化一直是研究组织分化基本原理的模型。我们已经广泛使用细胞培养模型来鉴定和表征骨骼肌分化过程中染色质重塑酶的功能。通过修改现有的方法，我们现在也能够检查染色质结构的变化和调节蛋白的相互作用，导致在胚胎肌发生过程中的基因激活和成人组织中的基因表达的激活和维持。最近的进展使我们能够检查肌细胞基因表达的调控，特别是在体节，在胚胎肌细胞发生的开始，这进一步扩展了我们的能力，了解在胚胎发育的背景下，肌细胞发生的分子控制。 该更新申请将重点关注SWI/SNF染色质重塑酶在几个水平上的功能。我们将研究SWI/SNF酶如何与肌源性转录因子和组蛋白修饰酶合作，以促进肌源性基因表达（AIm 1）的时间控制。我们将研究肌细胞发生所需的信号转导途径如何调节染色质重塑酶的功能（目的2）。最后，我们将研究SWI/SNF染色质重塑酶在细胞核中肌源性基因定位的分化依赖性重排中的功能，以及这一过程如何有助于肌源性基因表达的时间控制（目的3）。 公共卫生相关性：我们提出的研究在分子水平上解决胚胎和成人骨骼肌分化和维持过程中组织特异性基因表达的调节，将对我们对胚胎肌肉发育和成人肌肉再生的整体理解产生重大影响。这项工作也将增加我们对肌肉疾病中发生的变化的理解，其中肌肉生长增加（肥大）或肌肉发育减少（萎缩），以及横纹肌肉瘤的形成，这是肌源性肿瘤。

DESCRIPTION (provided by applicant): To understand normal development and differentiation, it is necessary to determine the mechanisms by which cells initiate new programs of gene expression and promote formation of specific cell lineages. Typically, this involves activation of genes that are transcriptionally silent and that are likely incorporated into repressive chromatin structure. Evidence supports the idea that differentiation specific transcriptional regulators and enzymes that remodel or alter chromatin structure cooperate to render genomic DNA more accessible to the transcriptional machinery. SWI/SNF enzymes remodel nucleosome structure in an ATP dependent manner and facilitate transcription factor function in vitro and in vivo. Components of these enzymes are essential for embryonic development and some act as tumor suppressors. Additionally, SWI/SNF enzymes interact with other known tumor suppressors and are implicated in cell cycle control. Thus these enzymes are broadly required for normal cell function and for differentiation and development, and their misregulation is implicated in tumor formation. Skeletal muscle differentiation has long been a model for studying fundamental principles of tissue differentiation. We have made extensive use of cell culture models to identify and characterize chromatin remodeling enzyme function during skeletal muscle differentiation. Via modification of existing methodologies, we are now also capable of examining changes in chromatin structure and regulatory protein interactions that lead to gene activation during embryonic myogenesis and during the activation and maintenance of gene expression in adult tissue. Recent advances allow us to examine the regulation of myogenic gene expression specifically in the somites, at the start of myogenesis in the embryo, which further extends our abilities to understand the molecular control of myogenesis in the context of embryonic development. This renewal application will focus on SWI/SNF chromatin remodeling enzyme function at several levels. We will investigate how SWI/SNF enzymes cooperate with myogenic transcription factors and histone modifying enzymes to promote temporal control of myogenic gene expression (AIm 1). We will investigate how signal transduction pathways required for myogenesis regulate chromatin remodeling enzyme function (Aim 2). Finally, we will investigate SWI/SNF chromatin remodeling enzyme function in the differentiation dependent rearrangement of myogenic gene positioning in the nucleus and how this process contributes to the temporal control of myogenic gene expression (Aim 3). PUBLIC HEALTH RELEVANCE: Our proposed studies addressing the regulation of tissue-specific gene expression during embryonic and adult skeletal muscle differentiation and maintenance at a molecular level will have significant impact on our overall understanding of muscle development in the embryo and muscle regeneration in the adult. This work will also increase our understanding of changes that occur in muscle diseases where increased muscle growth (hypertrophy) or reduced muscle development (hypotrophy) are exhibited and on the formation of rhabdomyosarcomas, which are tumors of myogenic derivation.