Molecular Mechanisms of Genetic Recombination

本研究的长期目标是了解同源基因重组的分子机制。这些目标是通过研究基因重组改变的突变体和通过研究促进重组的酶和重组过程中DNA的反应来实现的。本文主要研究了裂糖酵母（Schizosaccharomyces pombe）的减数分裂重组和大肠杆菌（Escherichia coli）的rebcd重组途径。这两种情况下的重组都与DNA双链断裂的形成和修复有关。S. pombe研究的具体目的是：1)分析减数分裂DNA断裂并确定其在重组中的作用；2)分离和分析重组后期改变的S. pombe突变体；3)评估重组在减数分裂染色体分离中的作用。在大肠杆菌中研究的具体目的是阐明RecBCD酶（一种移动重组机器）从双链端解绕DNA的机制。重组对于产生生物和细胞水平的多样性以及修复DNA双链断裂都是重要的。重组异常产生染色体重排，如缺失、易位和缺陷。这些重排与出生缺陷和癌症有关，也可能是其原因。了解重组的分子机制对于确定这些疾病的病因和可能的预防非常重要。

The long-term objective of the research proposed here is to understand the molecular mechanisms of homologous genetic recombination. These objectives are approached genetically by studying mutant organisms altered in recombination and biochemically by studying the enzymes promoting recombination and the reactions of DNA during recombination. The research is focused on meiotic recombination in the fission yeast Schizosaccharomyces pombe and on the RecBCD pathway of recombination in the bacterium Escherichia coli. Recombination in both of these situations is associated with the formation and repair of DNA double-strand breaks. Specific aims of the research in S. pombe are to 1) analyze meiotic DNA breaks and determine their role in recombination, 2) isolate and analyze S. pombe mutants altered in the late steps of recombination, and 3) assess the role of recombination in meiotic chromosome segregation. The specific aim of the research in E. coli is to elucidate the mechanism of DNA unwinding from a double-strand end by RecBCD enzyme, a traveling recombination machine. Recombination is important for generating diversity at both the organismal and cellular levels and for the repair of DNA double-strand breaks. Aberrancies of recombination generate chromosomal rearrangements, such as deletions, translocations, and deficiencies. These rearrangements are associated with, and may be a cause of, birth defects and cancers. Understanding the molecular mechanisms of recombination is important in determining the causes of these diseases and possibly preventing them.