Structure and Pharmacologic Modulation of the Mitotic Chromosome's Central Axis

项目摘要 有丝分裂染色体的形成对于真核生物遗传信息的传播是必不可少的。 分散的间期染色质转变为标志性的X形中期染色体 涉及三个主要事件：中轴（染色体“支架”）的形成，纵向 收缩和冷凝。已经提出了合理的理论来解释后两个事件， 收缩通过染色质环的挤压发生， 染色体材料的体积相变。相比之下， 有丝分裂支架，它的存在一直是相当大的争议的来源。直接 支架存在的证据最近来自于观察到的一个中心丝， 天然有丝分裂染色体进行体外受控扩增。这些细丝可以被释放出来， 完整的，从它的染色体限制仔细核溶解，为进一步研究提供了基础。 该建议旨在阐明有丝分裂染色体支架的基本原理，包括其 分子组成（目标1），其三维结构（目标2），以及其与 染色质包裹它（目的1和2）。所获得的信息将提供一个全球性的观点， 核心的有丝分裂染色体，解释其组成部分如何组装成一个结构的介观比例，以及这种结构如何组织基因组的方式，确保其忠实， 有效分配。所获得的知识将使更详细的调查机制支配支架组装和拆卸及其相互作用的性质与其他细胞 组件（例如，染色质、动粒）。 该提案还寻求开发支架组装的化学调节剂（目标3）。为 支架及其组分越来越多地被理解为在人类健康中发挥重要作用， 这些工具不仅能够进一步研究支架，而且还将允许在临床环境中对其进行药理学操作。例如，越来越多的恶性肿瘤涉及到支架成分（如冷凝素）的失调， 一种特殊的基因组不稳定性称为染色体不稳定性。基因组的不稳定性是 在癌细胞的演变中，促进它们逃避免疫清除和获得治疗抗性的因素。通过抑制导致染色体不稳定的途径，调节剂 凝聚素（和其他支架成分）的增加可能会限制癌症的进化潜力， 细胞

Project Summary Mitotic chromosome formation is essential for the dissemination of genetic information in eukaryotes. The conversion of dispersed interphase chromatin into the iconic, X-shaped metaphase chromosome involves three principal events: the formation of a central axis (the chromosomal “scaffold”), lengthwise contraction, and condensation. Plausible theories have been advanced to explain the latter two events, with contraction occurring through the extrusion of chromatin loops and condensation occurring through a volume phase transition of the chromosomal material. In contrast, little is known about the formation of the mitotic scaffold, and its very existence has been the source of considerable controversy. Direct evidence for the scaffold's existence has recently come from the observation of a central filament in native mitotic chromosomes subjected to controlled expansion ex vivo. This filament could be liberated, intact, from its chromosomal confines by careful nucleolysis, providing a basis for further study. This proposal aims to elucidate basic principles of the mitotic chromosome scaffold, including its molecular composition (Aim 1), its three-dimensional architecture (Aim 2), and its interactions with the chromatin enveloping it (Aims 1 and 2). The information obtained will provide a global view of the core of the mitotic chromosome, explaining how its components assemble into a structure of mesoscopic proportions and how this structure organizes the genome in a manner ensuring its faithful and efficient distribution. The acquired knowledge will enable more detailed investigations into the mechanisms governing scaffold assembly and disassembly and the nature of its interactions with other cellular components (e.g., chromatin, kinetochores). This proposal also seeks to develop chemical modulators of scaffold assembly (Aim 3). As the scaffold and its constituents are increasingly understood to play important roles in human health and disease, such tools will not only enable further research on the scaffold but will also allow for its pharmacological manipulation in clinical contexts. Dysregulation of scaffold components such as the condensins, for instance, has been implicated in a growing number of malignancies, where they contribute to a particular form of genome instability known as chromosome instability. Genome instability is a key factor in the evolution of cancer cells, facilitating their escape from immune clearance and their acquisition of therapeutic resistance. By suppressing a pathway leading to chromosome instability, modulators of condensins (and other scaffold components) may act to limit the evolutionary potential of cancer cells.