Sister Chromatid and Homolog Interactions in Meiosis

减数分裂中姐妹染色单体和同源物的相互作用

• 批准号: 0078138
• 负责人: Dean Dawson
• 金额: $ 37.5万
• 依托单位: Tufts University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-02-15 至 2004-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0078138&HistoricalAwards=false
• 关键词: Sister; Chromatid; Homolog; Interactions; Meiosis

Meiosis is the process used to generate haploid cells from diploid precursors. It is characterized by a single round of DNA replication followed by two rounds of chromosome segregation. In the first meiotic division, chromosomes pair with, then migrate away from, their homologues. A critical aspect of meiosis I is crossing-over, or exchange, between homologous chromosomes. This form of recombination may be part of a recognition process that allows chromosomes to align with their proper partner. This alignment culminates in formation of a proteinaceous structure, called the synaptonemal complex (SC), along the homologues. Crossovers also clearly play a role in providing a physical link between paired homologues, which allows the homologues to attach properly to spindle fibers that will mediate their segregation. Crossovers alone do not provide a stable linkage between homologues. Following DNA replication, each homologue is composed of two identical sister chromatids. The cohesion of these chromatids locks crossovers in place allowing the crossovers to act as a stable link between the homologues until anaphase I, at which time release of the sister arm cohesion allows the homologues to disjoin. Accordingly, mutants unable to completemeiotic recombination usually exhibit low fertility or sterility. However some organisms,including yeast, have mechanisms that insure the segregation of single pairs of chromosomesthat have failed to experience a crossover in an otherwise normal meiosis. This project addresses two questions. First, what types of interactions between chromosomes that have failed to experience an exchange enable them to segregate away from one another? Second, how do sister chromatids remain associated in meiosis I, thus helping crossovers to link homologues and ensuring that both sisters will stay joined until meiosis II? Experiments will test the model that interactions between the centromeres of test chromosomes mediate their disjunction at meiosis I. Cytological techniques will be used to test centromeric interactions occur between a pair of homeologues, specifically tagged with GFP. The second objective, to explore the behavior of sister chromatids in meiosis, will be addressed experimentally in three ways. First, experiments will be performed to determine whether the loss of meiotic sister cohesion observed in spo11 mutants (that do not initiate meiotic recombination) is due to a requirement for the Spo11 protein or alternatively a requirement for recombination initiation in meiotic sister chromatid cohesion. Second, the meiotic behavior of GFP-tagged sister chromatids will be observed cytologically in previously characterized meiotic mutants to explore the relationships of sister chromatid association, recombination and SC formation. Finally, the GFP tagged chromosomes will be monitored in a genetic screen to identify new genes involved in mediating proper sister chromatid behavior in meiosis. The experiments conducted in this work will help to elucidate the mechanism of chromosome segregation.

减数分裂是用于从二倍体前体产生单倍体细胞的过程。它的特征是一轮DNA复制，然后是两轮染色体分离。在第一个减数分裂师中，染色体与它们的同源物搭配，然后脱离它们。我在同源染色体之间越过或交换减数分裂的关键方面。这种形式的重组可能是识别过程的一部分，该过程允许染色体与其适当的伴侣保持一致。这种比对在沿着同源物沿着蛋白质结构（称为突发性复合物（SC）的形成，都达到顶点。跨界车还显然在配对同源物之间提供物理链接方面发挥了作用，这使得同源物可以适当地附着以旋转纤维，以介导其隔离。仅跨界车就不会在同源物之间提供稳定的联系。 DNA复制后，每个同源物由两个相同的姐妹染色单体组成。这些染色质的凝聚力将交叉锁定在适当的位置，使得交叉充当同源物之间的稳定链接，直到后期I，此时姊妹臂凝聚力的释放使同源物可以解开。因此，无法完成的突变体通常表现出低生育或不育。但是，某些生物（包括酵母）具有确保单对染色体对隔离的机制，但在原本正常的减数分裂中未能经历过交叉。 该项目解决了两个问题。首先，未能体验过交换的染色体之间的哪些类型的相互作用使它们能够彼此隔离？其次，姐妹染色单体如何在减数分裂I中保持联系，从而有助于跨界链接并确保两个姐妹都会保持加入直到减数分裂II？实验将测试该模型，即测试染色体的centromeres之间的相互作用介导其在减数分裂I上的分离I。细胞学技术将用于测试一对常字应之间发生的丝粒相互作用，该同源物特别标记了GFP。第二个目标是探索姐妹染色单体在减数分裂中的行为，将通过三种方式在实验中解决。首先，将进行实验，以确定在SPO11突变体中观察到的减数分裂姊妹内聚力的丧失（不启动减数分裂重组）是由于对SPO11蛋白的需求或对减数分裂姊妹染色剂凝聚的重组起始的要求。其次，将在先前表征的减数分裂突变体中观察到GFP标记的姐妹染色单体的减数分裂行为，以探索姐妹染色单体关联，重组和SC形成的关系。最后，将在遗传筛选中监测带有GFP标记的染色体，以鉴定参与减数分裂中介导适当的姐妹染色单体行为的新基因。这项工作中进行的实验将有助于阐明染色体隔离的机理。