How do Synaptonemal Complex Proteins Mediate Class I Crossover Formation?

 描述（由申请人提供）：减数分裂期间的染色体分离主要依赖于同源物间交叉重组事件产生的关联。在芽殖酵母和其他生物体中，错配修复蛋白复合物Msh 4/Msh 5和Mlh 1/Mlh 3是解决大部分交换所必需的，沿着的蛋白质组装成引人注目的蛋白质性染色体结构，即联会复合物（SC）。在芽殖酵母中，Zip 1是三重SC结构的横丝的组成部分，其位于纵向对齐的同源染色体的界面处。SC蛋白、全长SC结构和交叉成熟之间的关系尚不清楚。我们最近的研究涉及种间互补实验已经揭示，有点令人惊讶的是，Zip 1的祖先版本有能力促进在芽殖酵母中的交叉依赖于其他芽殖酵母SC蛋白和Mlh 3，但独立于全长SC，独立于Msh 4功能。这些数据已经把我们的注意力转向研究，将确定Zip 1和其他SC蛋白介导的交叉成熟的分子特征，并对实验，将SC和Msh 4独立，I类交叉事件的特点。我们提出的实验采用直接的遗传、生物化学和显微镜方法来1）进一步表征在交叉熟练的、突触缺陷的zip 1等位基因的背景下发生的交叉形成，2）鉴定Zip 1和其他突触蛋白的残基，这些残基对于交叉功能是重要的，以及3）表征在交叉位点处形成的突触起始复合物结构内的SC蛋白的结构和动力学。我们采用的高通量筛选方法与实验室的专业知识及其对众多高级本科生的访问非常匹配。我们的研究的总和将有助于我们理解的结构和分子机制（包括洞察可能的祖先机制），促进适当的同源分离酵母的重要细节。我们希望这些目标有助于多个高质量的研究论文，由两名本科生和一名博士生撰写，这将是相关的广泛的减数分裂和染色体动力学领域。

 DESCRIPTION (provided by applicant): Chromosome disjunction during meiosis relies critically on associations that are generated by interhomolog crossover recombination events. In budding yeast and other organisms, the mismatch repair protein complexes Msh4/Msh5 and Mlh1/Mlh3 are required for the resolution of a large proportion of crossovers, along with proteins that assemble a striking proteinaceous chromosomal structure, the synaptonemal complex (SC). In budding yeast, Zip1 is a component of the transverse filaments of the tripartite SC structure, which lies at the interface of lengthwise-aligned homologous chromosomes. The relationship between SC proteins, the full- length SC structure and crossover maturation is unclear. Our recent studies involving an interspecies complementation experiment have revealed, somewhat surprisingly, that an ancestral version of Zip1 has the capacity to promote crossovers in budding yeast that are dependent on other budding yeast SC proteins and on Mlh3, but independent of the full-length SC, and independent of Msh4 function. These data have turned our attention toward studies that will identify the molecular features of Zip1 and the other SC proteins that mediate crossover maturation, and toward experiments that will characterize SC- and Msh4-independent, class I crossover events. Our proposed experiments employ straightforward genetic, biochemical, and microscopy approaches to 1) further characterize the crossover formation that occurs in the context of a crossover- proficient, synapsis-defective zip1 allele, 2) identify residues of Zip1 and other synapsis proteins that are important for a crossover function, and 3) characterize the structure and dynamics of SC proteins within the synapsis initiation complex structures formed at crossover sites. The high-throughput screening approaches that we employ are well matched to the expertise of the lab and its access to numerous advanced undergraduate students. The sum of our studies will contribute important details to our understanding of the structures and molecular mechanisms (including insight into possible ancestral mechanisms) that promote proper homolog disjunction in yeast. We expect these Aims to contribute to multiple high quality research papers, authored by two undergraduates and a doctoral student, which will be relevant to the broad meiosis and chromosome dynamics fields.