Homologous Recombination and DNA Double-strand Breaks

1.关于波长重组的双链断裂修复模型。(1)证实了双链缝隙修复。(2)redpha和redbeta只是这种修复所必需的lambda基因。(3)大肠杆菌的recA、recBC、recD、recJ、recN和ruvB基因功能不是必需的。(4)RecA蛋白可能影响杂交和非杂交的选择。我们建立了一个允许回收两种重组产物的质粒转移系统，结果表明：(1)大肠杆菌的recf途径是非互惠的。(2)双链断裂刺激重组，夸大了这种非互易性。(3)这些结果支持“连续半交叉模型”，该模型认为，一个重组事件导致DNA末端，然后刺激下一个重组事件。在大肠杆菌的Ress途径中，我们证明了以下几点：(1)双链断裂刺激双链缝隙的相互修复。(2)双链末端的修饰使重组成为非互易的，但不改变其频率。(3)这些结果使我们建立了一个模型，在该模型中，双链间隙的产生导致了以下三种途径之一：非互易重组、有交换的可逆双链间隙修复和无互换的可逆双链间隙修复。我们用BPV质粒分析了哺乳动物的同源重组，特别是基因打靶。

1. On double-strand break repair model for recombination by lambda. (1) Proved double-strand gap repair. (2) Redalpha and redbeta are only lambda genes essential to this repair. (3) RecA, recBC, recD, recJ, recN, and ruvB gene functions of E. coli are not essential. (4) RecA protein might affect choice between crossover and non-crossover.2. We made a plasmid transfer system that allows recovery of both products of recombination and showed:(1) RecF pathway of E. coli is non-reciprocal. (2) A double-strand break stimulates recombination exaggerating this non-reciprocal nature. (3) These results support "successive half crossing-over model", which proposes that one event of recombination makes a DNA end that then stimulates a next event of recombination.3. We demonstrated the following in RecE pathway of E. coli: (1) A double strand break stimulates reciprocal double-strand gap repair. (2) Modification of a double strand end makes recombination non-reciprocal but does not alter its frequency. (3) These results led us to a model in which creation of a double-strand gap leads to one of the following three pathways: non-reciprocal recombination, reciprocal double-strand gap repair with crossing-over, and reciprocal double-strand gap repair without crossing-over.4. We analyzed mammalian homologous recombination especially gene targeting with BPV plasmid.