ANALYSIS OF MEIOTIC CHROMOSOME SYNAPSIS IN YEAST

减数分裂是有性繁殖生物的一个基本过程 为了将生殖细胞中的染色体数量减少一半而进行。 这种减少是必要的，这样当两个配子在 受精：细胞的二倍体染色体数目重组。 当减数分裂失败时，就会产生染色体不平衡的配子。在哺乳动物身上， 由这种染色体不平衡的受精卵产生的受精卵 配子通常是不能存活的，并占了大量的 自然流产。在产生可存活后代的情况下， 智力和形态缺陷，如21三体 (唐氏综合征)。了解减数分裂过程是如何 精确分离同源染色体的工作最终可能会 提供监视和预防故障所需的知识 进程。 为了使同源染色体在一开始就能正确分离 减数分裂，它们必须首先通过 形成一种称为联会复合体的多蛋白质结构 (SC)。拟议拨款的重点是确定SC是如何 在减数分裂过程中组装以及它如何起到指导分离的作用 在酵母减数分裂I时将同源染色体定位到相反的两极 酿酒酵母。两个基因RUM17和RUM18是最近发现的 利用减数分裂相关基因的特异性筛选进行鉴定 染色体突触。这些基因中的突变者表现出水平降低的 同源重组和孢子存活率下降。此外, 一种名为hcs1-7的酰基转移酶能够 特异性抑制联会复合体成分中的缺陷 霍皮，将接受调查。为了找到更多重要的基因 对于突触，两个基因屏幕，高复制抑制和合成 孢子致死，将使用特选的等位基因 HOP1、Red1、MEK1和HCS1-7。由基因引起的基因突变 将分析筛选对SC形成、重组的影响 和染色体分离来评估它们的功能。生化 使用纯化的蛋白质和提取物的组合的实验将 以确定相互作用的基因产物 从基因上讲，这是通过直接的物理相互作用实现的。具体地说 Red1与HOP1物理交互的模型，以及 霍皮是一种底物，将对MEK1激酶进行检测。通过组合 遗传、生化和细胞学研究，更好地了解 SC的功能、结构和组装途径将是 获得。

Meiosis is a fundamental process that sexually reproducing organisms undergo in order to reduce by half the chromosome number in germ cells. This reduction is necessary so that when two gametes fuse at fertilization the diploid chromosome number of the cell is reconstituted. When meiosis fails, chromosomally imbalanced gametes result. In mammals, the zygotes generated by fertilization of such chromosomally imbalanced gametes are frequently inviable and account for a large number of spontaneous abortions. In cases where viable offspring are produced, mental and morphological defects such as those seen for Trisomy 21 (Down's syndrome) are observed. Understanding how the meiotic process works to accurately segregate homologous chromosomes may ultimately provide the knowledge needed to monitor and prevent failures of the process. In order for homologous chromosomes to segregate properly at the first meiotic division, they must first become physically associated by formation of a multi-protein structure called the synaptonemal complex (SC). The focus of the proposed grant is to determine how the SC is assembled during meiosis and how it functions to direct the segregation of homologous chromosomes to opposite poles at Meiosis I in the yeast Saccharomyces cerevisiae. Two genes, RUM17 and RUM18, have been recently identified using a screen specific for genes involved in meiotic chromosome synapsis. Mutants in these genes exhibit reduced levels of interhomolog recombination and decreased spore viability. In addition, the mechanism by which an acyltransferase, HCS1-7, is able to specifically suppress a defect in the synaptonemal complex component HOPI, will be investigated. In order to find additional genes important for synapsis, two genetic screens, high copy suppression and synthetic spore lethality, will be performed using specially selected alleles of HOP1, RED1, MEK1 and HCS1-7. Mutations in genes arising from the genetic screens will analyzed for their effects on SC formation, recombination and chromosome segregation to assess their functions. Biochemical experiments using a combination of purified proteins and extracts will be performed to determine whether gene products which interact genetically do so by a direct physical interaction. Specifically the model that RED1 physically interacts with HOP1, as well as the model that HOPI is a substrate for the MEK1 kinase will be tested. By combining genetic, biochemical and cytological studies, a greater understanding of the function, structure and pathway of assembly of the SC will be obtained.