Control of Programmed Replication fork Arrest by Chromosome Kissing

描述（由申请人提供）：据报道，癌细胞中的主要DNA处理（如转录、发育、X染色体失活和染色体易位）由称为“染色体接吻”的染色体与染色体接触控制，该接触由称为Reb 1的myb样终止子蛋白介导。我们最近在《细胞》杂志上发表的一篇论文中表明，裂变酵母中的染色体接吻也通过控制序列特异性的、生理程序化的叉停滞来控制复制叉的运动。这一发现提出了一些主要问题：（i）哪些蛋白质参与控制染色体接吻，它们的作用机制是什么？(ii)什么是程序化叉停的机制？在解决第一个问题的背景下，我们已经发现，两个染色质重塑蛋白的裂变酵母调节程序性叉逮捕。这意味着，这些重塑通过调节染色体接吻和核小体在复制末端的分布来做到这一点。该计划的目标之一是在全基因组搜索中发现调节染色体接吻的蛋白质，并试图了解它们的作用机制。该提案的另一个重要目标是通过测试这是通过MCM 2 -7解旋酶的单向停滞而发生的假设来揭示程序化叉停滞的作用机制。程序性叉停滞控制其他染色体的处理，如重组、基因沉默和转录传递，并且处于复制和其他过程的间期。最后，实验提出了本地化全基因组Reb 1依赖的复制末端。该目标的目的是检验两个假设：（i）天然存在的非典型弱位点通过染色体亲吻和/或DNA成环依赖性与强典型位点的相互作用而具有功能，并且这是这些长程蛋白质- DNA相互作用的一个功能;（ii）成环依赖性（或独立）叉停滞的功能是防止复制和转录之间的干扰。

DESCRIPTION (provided by applicant): Major DNA transactions such as transcription, development, X-chromosome inactivation and chromosomal translocations in cancer cells were reported to be controlled by chromosome to chromosome contacts called "chromosome kissing" mediated by a myb-like terminator protein called Reb1. We have recently shown in a paper to be published in Cell that chromosome kissing in fission yeast also controls replication fork movement by controlling sequence-specific, physiologically programmed fork arrest. This finding raises some major questions: (i) which proteins are involved in controlling chromosome kissing and what are their mechanisms of action?; (ii) what is the mechanism of programmed fork arrest? In the context of addressing the first question, we have discovered that two chromatin remodeling proteins of fission yeast modulate programmed fork arrest. The implication is that these remodelers do this by modulating chromosome kissing and nucleosome disposition about the replication termini. One of the goals of this proposal is to discover in a genome-wide search the proteins that modulate chromosome kissing and try to understand their mechanism of action. Another important goal of this proposal is to uncover the mechanism of action of programmed fork arrest by testing the hypothesis that this happens by unidirectional arrest of the MCM2-7 helicase. Programmed fork arrest controls other chromosome transactions such as recombination, gene silencing and transcriptional passage and is at the interphase of replication and other processes. Finally, experiments are proposed to localize genome-wide Reb1-dependent replication termini. The objectives of this goal is to test two hypotheses: (i) naturally occurring, noncanonical weak sites are rendered functional by chromosome kissing and/or DNA looping -dependent interaction with strong canonical sites and that is one function of these long range protein- DNA interactions; (ii) a function of looping-dependent (or independent) fork arrest is to prevent interference between replication and transcription.