Homologous chromosome pairing during meiosis in yeast

描述（由申请人提供）：我们的目标是了解同源重组和端粒组织如何在减数分裂中促进同源染色体的并列。这些过程对于i后期染色体分离是必不可少的。这些过程中的缺陷会导致非整倍体配子，从而导致人类的出生缺陷。这些过程背后的机制（双链断裂修复、端粒完整性和染色体组织）直接促成了癌细胞的发生。同源物如何配对是减数分裂研究中一个未解之谜。我们建议用出芽酵母进行实验，以解决两个核心问题：i)碱基配对相互作用在多大程度上促进了同源染色体相互寻找的能力？ii)端粒的动态组织、重组和紧密、稳定的同源并置（CSHJ）之间的机制联系。我们的假设是，重组的具体机械步骤部分取决于端粒的完整性，位置或运动。这一步是稳定入侵链的中间体。端粒结合蛋白Ndj1在减数分裂中参与连接端粒功能与染色体重组和分离。我们提出染色质结构和DNA损伤检查点蛋白在实现CSHJ中的作用。1. 我们将确定导致CSHJ的减数分裂重组的机制步骤。我们将使用一种新的定量分析，报告两个染色体位点的相对空间位置或可及性。2. 我们将确定影响减数分裂重组的减数分裂端粒重组的具体特征。我们将探讨空间约束、染色体运动的潜在作用，以及Ndj1或其他已知端粒结合蛋白在重组中的可能直接作用。3. 我们将通过突变确定与Ndj1协同作用的基因，以促进链入侵中间体的稳定。将采取全基因组和候选基因方法。胎儿描述：胚胎染色体数目异常（如21三体或唐氏综合症）导致妊娠流产和出生缺陷。这项研究的重点是了解染色体如何正确地分布到精子和卵细胞。我们的发现将影响子孙后代的健康。

DESCRIPTION (provided by applicant): Our objective is to understand how homologous recombination and telomere organization contribute to the juxtaposition of homologous chromosomes in meiosis. These processes are essential to proper chromosome segregation at anaphase I. Defects in these processes can lead to aneuploid gametes, which contribute to birth defects in humans. Mechanisms underlying these processes (double-strand break repair, telomere integrity and chromosome organization) contribute directly to the genesis of cancer cells. How homologs pair is a major unanswered question in the study of meiosis. We propose experiments using budding yeast to address two central questions: i) to what extent do base-pairing interactions contribute to the ability of homologous chromosomes to find one another? And ii) what defines the mechanistic link between dynamic organization of telomeres, recombination, and close, stable homolog juxtaposition (CSHJ). Our hypothesis is that a specific mechanistic step of recombination depends in part on telomere integrity, position or motion. This step is the stabilization of strand-invasion intermediates. A telomere-bound protein, Ndj1, is involved in linking telomere function to chromosome recombination and segregation in meiosis. We propose roles for chromatin structure and DNA damage checkpoint proteins in achieving CSHJ. 1. We will determine the mechanistic step(s) in meiotic recombination that lead to CSHJ. We will use a new quantitative assay that reports on the relative spatial position or accessibility of two chromosomal loci. 2. We will determine the specific features of meiotic telomere reorganization that impact meiotic recombination. We will explore the potential roles of spatial constraint, chromosome motion and a possible direct role in recombination by Ndj1 or other known telomere-bound proteins. 3. We will identify genes by mutation that act in concert with Ndj1 to promote the stabilization of strand invasion intermediates. Genome-wide and candidate gene approaches will be taken. Lay description: Pregnancy loss and birth defects result from embryos having abnormal chromosome numbers (e.g. trisomy 21 or Downs syndrome). This research focuses on understanding how chromosomes are properly distributed to sperm and egg cells. Our findings will impact health of future generations.