A Molecular Genetic Analysis of Meiotic Chromosome Nondisjunction

这项工作的长期目标是了解减数分裂特异性结构，如突触复合体和重组结节，如何在减数分裂染色体修复、重组和分离中组织和起作用。研究表明，多组分结构中亚基化学计量的改变会扰乱这些结构的功能。作为鉴定酵母减数分裂特异性结构成分的新颖的第一步，细胞受到携带在质粒上的野生型酵母DNA的挑战，每个细胞复制100个或更多拷贝。一项对减数分裂染色体不分离的灵敏测定使鉴定携带插入物的质粒成为可能，这些插入物专门导致减数分裂染色体分离错误或阻止减数分裂完成。已经发现41个这样的质粒携带不同的插入物。初步结果表明，一些质粒含有先前从隐性突变体中发现的减数分裂基因；其他质粒含有新的基因，其中一些可能在以前的搜索中由于与其他基因的功能重叠而被遗漏。鉴于酵母基因组序列即将完成，后一类基因的鉴定尤其及时，这将极大地促进基因家族功能的分析。这里提出的工作是(1)对质粒收集进行二次筛选，以鉴定最有可能直接参与减数分裂染色体分离的基因；(2)对一个亚群进行免疫细胞学研究，以鉴定作为减数分裂染色体结构组成部分的基因产物。通过鉴定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功能，这些酵母模型系统的研究将有助于理解包括人类在内的真核生物细胞如何在有性生物生殖周期的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. ***