A Molecular Genetic Analysis of Meiotic Chromosome Nondisjunction

9507089 Dresser这项工作的长期目标是了解减数分裂特有的结构，如联会复合体和重组结节，是如何组织起来的，并在减数分裂染色体修复、重组和分离中发挥作用。已有研究表明，多组分结构中亚基化学计量比的变化可能会干扰这些结构的功能。作为鉴定酿酒酵母减数分裂特异结构成分的新的第一步，细胞受到野生型酵母DNA的挑战，这些DNA携带在每个细胞复制到100个或更多拷贝的质粒上。一种敏感的减数分裂染色体不分离分析方法使鉴定携带能导致减数分裂染色体分离错误或阻止减数分裂完成的插入片段的质粒成为可能。已经发现了41个携带不同插入片段的这样的质粒。初步结果表明，其中一些质粒含有先前从隐性突变体搜索中鉴定出的减数分裂基因；另一些质粒含有新基因，其中一些可能由于与其他基因功能重叠而在以前的搜索中被遗漏。鉴于酵母基因组序列即将完成，对后一类基因的鉴定尤其及时，这将极大地促进对基因家族功能的分析。本文提出的工作是(1)对质粒库进行二次筛选，以确定最有可能直接参与减数分裂染色体分离的基因；(2)对一个子集进行免疫细胞学研究，以确定构成减数分裂染色体结构的基因产物。通过识别和分析减数分裂中染色体修复、重组和分离所需的新基因和新功能，这些在酵母模型系统中的研究将有助于理解包括人类在内的真核细胞如何在有性生物生殖周期的这一关键时期保持其基因组的完整。减数分裂中的错误会导致下一代细胞的染色体数量异常或细胞死亡。***

9507089 Dresser The long-range goal of this work is to understand how meiosis-specific structures, such as synaptonemal complexes and recombination nodules, are organized and function in meiotic chromosome repair, recombination and segregation. It has been shown that alterations in the stoichiometry of subunits in multicomponent structures can perturb the function of those structures. As a novel first step toward identifying the components of the meiosis-specific structures in the yeast Saccharomyces cerevisiae, cells have been challenged with wild-type yeast DNA carried on plasmids that replicate to 100 or more copies per cell. A sensitive assay for meiotic chromosome nondisjunction has made it possible to identify plasmids carrying inserts that specifically cause errors in meiotic chromosome segregation or prevent the completion of meiosis. Forty-one such plasmids carrying different inserts have been found. Preliminary results indicate that some of the plasmids contain meiotic genes previously identified from recessive mutant hunts; other plasmids contain novel genes, some of which are likely to have been missed in previous searches due to functional overlaps with other genes. Identification of genes in the latter class is particularly timely given the impending completion of the yeast genome sequence, which will greatly facilitate analysis of the functions of families of genes. The work proposed here is (1) to conduct secondary screens on the plasmid collection to identify genes most likely to be directly involved in meiotic chromosome segregation, and (2) to perform immunocytological studies on a subset to identify gene products that are components of meiotic chromosome structures. %%% By identifying and analyzing novel genes and functions required for chromosome repair, recombination and segregation in meiosis, these studies in the yeast model system will contribute to an understanding of how cells in eukaryotes, including humans, keep their genomes intact during this critica l period in the reproductive cycle of sexual organisms. Errors in meiosis can result in cells of the next generation having an abnormal number of chromosomes or in cell death. ***