How Do Synaptonemal Complex Proteins Promote Crossover Recombination and Synapsis?

项目摘要 我们提出的研究旨在破译构成同源染色体的分子机制。 生殖细胞形成过程中的分离。减数分裂是专门的细胞分裂周期，它将 每条染色体的两个同源拷贝(同源)以分离子核，有效地减少了 染色体倍性。染色体分离错误导致非整倍体生殖细胞也携带 多条或两条染色体。同源基因分离成功的关键是事先建立 复制的染色体之间短暂但稳定的联系；对大多数生物体来说，这些联系是形成的 通过同源交叉重组事件，结合完整的姐妹凝聚力。 如何在减数分裂过程中有效地在每对染色体之间产生交叉事件仍然存在 人们对此知之甚少，但对大多数生物体来说，很明显，这个过程涉及到一种精致的协调 大规模染色体运动和局部DNA修复过程之间的关系。一种保守的多蛋白质 结构，联会复合体(SC)，调节同源伙伴之间的亲密排列 染色体的轴心，形成DNA修复中间体成熟的物理环境。SC已经很长时间了 与成功的交叉重组有关，尽管我们最近的研究表明 SC结构本身对于芽期酵母的杂交是必不可少的，我们还证明了SC构筑 区块成分ZIP1在促进杂交方面具有遗传上可分离的功能。我们的结构和功能 分析发现，ZIP1的S N末端的相邻结构域独立地发挥促进交叉的作用 重组和SC组装，可能通过与亲交叉E3相扑单独接口 连接酶、Zip3和SC中心元件蛋白复合体Ecm11-Gmc2。 我们最近的数据显示，在ZIP1的S N末端有一个潜在的基于磷酸化的开关，它控制着 它的交叉活性，ii)确定了Zip3蛋白中的几个区域，这些区域是它的前重组所必需的 和/或支持SC的组装活动，iii)缩小了ECC11和GMC2之间的最小相互作用界面， 和iv)证实了前交叉蛋白(以及可能的SC中心)之间的邻近标记相互作用 元素蛋白)，由ZIP1‘S N末端稳定。我们提议的实验，旨在 支持为几个本科生、一个新的五年级硕士学生提供独特的丰富的培训环境，以及 一名博士生，在我们最近的实验数据的基础上，旨在深化我们的结构和功能 了解酿酒酵母中协调重组和SC组装的分子机制。

Project Summary Our proposed research aims to decipher the molecular mechanisms that underlie homologous chromosome segregation during reproductive cell formation. Meiosis is the specialized cell division cycle that partitions the two homologous copies of every chromosome (homologs) to separate daughter nuclei, effectively reducing chromosome ploidy. Errors in chromosome segregation lead to aneuploid reproductive cells that carry too many or two few chromosomes. Key to the success of homolog segregation is the prior establishment of transient but stable associations between replicated chromosomes; for most organisms these links are formed by interhomolog crossover recombination events, in conjunction with intact sister cohesion. How crossover events are efficiently generated between every chromosome pair during meiosis remains poorly understood, but for most organisms it is clear that the process involves an exquisite coordination between large-scale chromosome movements and local DNA repair processes. A conserved multi-protein structure, the synaptonemal complex (SC), mediates an intimate alignment between homologous partner chromosome axes and forms the physical context in which DNA repair intermediates mature. SC has long been associated with successful crossover recombination, and although our recent research demonstrated that the SC structure per se is dispensable for crossing over in budding yeast, we also showed that the SC building block component, Zip1, has a genetically separable function in promoting crossovers. Our structure-function analysis revealed adjacent domains within Zip1’s N terminus that function independently to promote crossover recombination and SC assembly, potentially through separately interfacing with the pro-crossover E3 SUMO ligase, Zip3, and the SC central element protein complex Ecm11-Gmc2. Our recent data has i) revealed a potential phosphorylation-based switch in Zip1’s N terminus that controls its crossover activity, ii) identified several regions within the Zip3 protein required for its pro-recombination and/or pro-SC assembly activities, iii) narrowed the minimal interaction interface between Ecm11 and Gmc2, and iv) demonstrated proximity labeling interactions between pro-crossover proteins (and possibly SC central element proteins) that are stabilized by Zip1’s N terminus. Our proposed experiments, which are designed to support a uniquely rich training environment for several undergraduates, a new “5th year” Masters student, and one doctoral student, build upon our recent experimental data and aim to deepen our structural and functional understanding of the molecular mechanisms that coordinate recombination and SC assembly in S. cerevisiae.