Cohesin Polycomb Interactions in Gene Regulation

描述（由申请人提供）：拟议工作的长期目标是确定姐妹染色单体凝聚蛋白如何控制基因转录。这将阐明某些人类遗传综合征和癌症的机制。在细胞分裂之前，粘着蛋白拓扑地环绕姐妹染色单体将它们保持在一起。适度降低粘着蛋白活性不会破坏染色单体的凝聚力，但会改变基因转录，导致生长和发育不良。高粘附素活性与多种癌症的预后不良有关。 粘着蛋白如何控制转录在很大程度上是未知的，但目前的证据表明，它直接参与多种机制。最近的发现提出了一种新的范式，其中粘附素和多梳抑制复合物1（PRC 1）表观遗传沉默复合物之间的平衡在全球范围内控制许多活性基因的基因沉默和转录。这些数据表明，粘附素直接促进PRC 1与活性基因的结合，其中PRC 1阻止启动子处暂停的RNA聚合酶II（Pol II）过早进入延伸。他们还表明，活性基因上的粘着蛋白隔离PRC 1，从而控制有多少可用于基因沉默，PRC 1限制了沉默和活性基因上的粘着蛋白结合。这项提议的目的是测试这种新的模式，并确定cohesin和PRC 1共同控制基因沉默和活性基因转录的机制。 拟议的研究结合了联合收割机生物化学，遗传学，基因组学和生物物理学的方法来测试当前模型的关键预测。目的1测试的想法，粘附素物理相互作用与PRC 1直接促进PRC 1结合到活性基因启动子，PRC 1限制粘附素结合，通过与粘附素加载或去除因子的相互作用。目的2测试PRC 1通过促进NELF和DSIF暂停因子或Pol II激酶活性来防止暂停的Pol II过早进入伸长的想法。这些研究所提供的对粘附素和PRC 1控制转录的机制的深入了解，应该为纠正遗传综合征和癌症中粘附素-PRC 1失衡提供新的方法。

DESCRIPTION (provided by applicant): The long-term goal of the proposed work is to determine how sister chromatid cohesion proteins control gene transcription. This will illuminate mechanisms that underlie certain human genetic syndromes and cancers. Cohesin topologically encircles sister chromatids to hold them together until a cell divides. Moderate reductions in cohesin activity don't disrupt chromatid cohesion, but alter gene transcription, leading to poor growth and development. High cohesin activity is linked to poor prognosis in multiple cancers. How cohesin controls transcription is largely unknown, but current evidence argues that it participates directly in multiple mechanisms. Recent discoveries argue for a new paradigm in which a balance between cohesin and the Polycomb Repressive Complex 1 (PRC1) epigenetic silencing complex globally controls both gene silencing and transcription of many active genes. The data argue that cohesin directly facilitates binding of PRC1 to active genes, where PRC1 prevents paused RNA polymerase II (Pol II) at the promoter from prematurely entering into elongation. They also suggest that cohesin at active genes sequesters PRC1, thereby controlling how much is available for gene silencing, and that PRC1 limits cohesin binding at silenced and active genes. The goal of this proposal is to test this new paradigm, and determine the mechanisms by which cohesin and PRC1 together control both gene silencing and transcription of active genes. The proposed studies combine biochemical, genetic, genomic, and biophysical approaches to test key predictions of the current model. Aim 1 tests the ideas that cohesin physically interacts with PRC1 to directly facilitate PRC1 binding to active gene promoters, and that PRC1 limits cohesin binding through interactions with cohesin loading or removal factors. Aim 2 tests the idea that PRC1 prevents premature entry of paused Pol II into elongation by facilitating NELF and DSIF pausing factor or Pol II kinase activities. The insights into the mechanisms by which cohesin and PRC1 control transcription provided by these studies should suggest new methods for correcting cohesin-PRC1 imbalances in genetic syndromes and cancer.