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内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背后的机制。从拓扑结构上讲，内聚蛋白将姐妹染色单体包围在一起，直到细胞分裂。内聚活性的适度降低不会破坏染色单体内聚，但会改变基因转录，导致生长发育不良。高黏结蛋白活性与多种癌症的不良预后有关。内聚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，即内聚蛋白和多梳抑制复合体1 （Polycomb suppression Complex 1, PRC1）表观遗传沉默复合体之间的平衡在全球范围内控制着许多活性基因的基因沉默和转录。数据表明，内聚蛋白直接促进了PRC1与活性基因的结合，其中PRC1阻止启动子处暂停的RNA聚合酶II （Pol II）过早进入延伸。他们还认为，活性基因上的内聚蛋白会隔离PRC1，从而控制基因沉默的可用量，而PRC1限制了内聚蛋白与沉默基因和活性基因的结合。本研究的目标是验证这一新范式，并确定内聚蛋白和PRC1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。Aim 1验证了粘合蛋白与PRC1物理相互作用直接促进PRC1与活性基因启动子结合的观点，以及PRC1通过与粘合蛋白装载或去除因子相互作用限制粘合蛋白结合的观点。目的2验证了PRC1通过促进NELF和DSIF暂停因子或Pol II激酶活性来阻止暂停的Pol II过早进入延伸的观点。这些研究提供的关于内聚蛋白和PRC1控制转录的机制的见解，应该为纠正遗传综合征和癌症中内聚蛋白-PRC1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.