Illegitimate recombination by drug resistance elements

描述(申请人提供)：我们希望了解管理染色体功能的基本原则，特别是涉及不同过程之间的空间、时间和功能协调的原则。建议的研究强调不同有机体之间的综合比较，分为四类。首先，我们将探讨最近发现的大肠杆菌染色体动力学的几个方面：三维排列、移动性；姐妹染色体之间的粘合和丧失(这发生在一个与真核有丝分裂中的事件惊人地相似的一致过程中，并对高等生物的染色体分离机制的进化发展具有影响)；起源附近区域的特殊行为；以及染色体状态和细胞分裂的连锁。其次，我们将进一步探索我们的发现，即酵母ATR同源基因Mec1基于染色体的信号转导通过特定的、基因定义的“慢区”介导DNA复制的调节进展。这一过程对DNA脆性部位的起源、激发和性质的调控具有重要意义。这些过程很可能是高等真核生物事件的典范。提出了遗传、物理和细胞学研究。第三，我们将继续对重组和染色体结构之间的功能相互作用进行研究。这项工作的一个方面涉及丝状真菌大孢子菌减数分裂的细胞遗传学研究。我们将进一步研究细线/合线转变过程中局部重组介导的轴失稳，通过突触前排列的重组介导的同系轴并置，纺锤体检查点蛋白在早期事件监测中的作用，以及选定的凝聚力和轴成分在轴发育中的作用。第二个方面将继续我们最近对有丝分裂断裂启动的重组的物理研究，首次确定参与这一过程的联合分子。突变研究将进一步定义物种和细胞周期变异，并探索对生化和染色体结构成分的要求。第四，我们将通过(I)开发评估热重复结构域的机械特性的方法；(Ii)探索磁力的新用途来探索染色质和整个染色体的机械特性；以及(Iii)使用我们最近开发的3C分析来探索双链断裂对染色质状态的局部影响，从而考虑染色体的机械特性。

DESCRIPTION (provided by applicant): We wish to understand basic principles that govern chromosome function, especially those involving spatial, temporal and functional coordination among different processes. Proposed research emphasizes synthetic comparisons among different organism and falls into four categories. First, several aspects of E.coli chromosome dynamics stemming from recent findings will be explored: three-dimensional disposition, mobility; cohesion and loss of cohesion between sister chromosomes (which occurs in a concerted process strikingly analogous to events in eukaryotic mitosis and has implications for the evolutionary development of chromosome segregation mechanisms in higher organisms); specialized behaviors of a peri-origin domain; and interlinkage of chromosome status and cell division. Second, we will further explore our finding that chromosome-based signal transduction by the yeast ATR homolog Mec1 mediates regulated progression of DNA replication through specific, genetically-defined "slow zones". This process has implications for regulation of origin firing and the nature of DNA fragile sites. These processes are likely paradigmatic for events in higher eukaryotes. Genetic, physical and cytological studies are proposed. Third, we will continue ongoing studies of functional interplay between recombination and chromosome structure. One aspect of this work involves cytogenetic studies of meiosis in the filamentous fungus Sordaria macrospora. We will further investigate local recombination-mediated axis destabilization at the leptotene/zygotene transition, recombination-mediated juxtaposition of homolog axes via presynaptic alignment, roles of spindle checkpoint proteins in surveillance of prophase events and roles of selected cohesion and axis components in axis development. A second aspect will continue our recent physical studies of mitotic break-initiated recombination which, for the first, time, identify joint molecules involved in this process. Species and cell cycle variations will be further defined and requirements for biochemical and chromosome structure components will be probed by mutant studies. Fourth, we will consider mechanical properties of chromosomes by (i) developing ways to assess mechanical properties of HEAT repeat domains; (ii) exploring novel uses of magnetic forces to probe the mechanical properties of chromatin and whole chromosomes; and (iii) using our recently developed 3C analysis to explore local effects of double-strand breaks on chromatin state.