Briggs Geoffrey S, Mahdi Akeel A, Weller Geoffrey R, Wen Qin, Lloyd Robert G
Institute of Genetics, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UK.
Philos Trans R Soc Lond B Biol Sci. 2004 Jan 29;359(1441):49-59. doi: 10.1098/rstb.2003.1364.
Recent studies in Escherichia coli indicate that the interconversion of DNA replication fork and Holliday junction structures underpins chromosome duplication and helps secure faithful transmission of the genome from one generation to the next. It facilitates interplay between DNA replication, recombination and repair, and provides means to rescue replication forks stalled by lesions in or on the template DNA. Insight into how this interconversion may be catalysed has emerged from genetic, biochemical and structural studies of RecG protein, a member of superfamily 2 of DNA and RNA helicases. We describe how a single molecule of RecG might target a branched DNA structure and translocate a single duplex arm to drive branch migration of a Holliday junction, interconvert replication fork and Holliday junction structures and displace the invading strand from a D loop formed during recombination at a DNA end. We present genetic evidence suggesting how the latter activity may provide an efficient pathway for the repair of DNA double-strand breaks that avoids crossing over, thus facilitating chromosome segregation at cell division.
最近对大肠杆菌的研究表明，DNA复制叉与霍利迪连接体结构的相互转化是染色体复制的基础，并有助于确保基因组从上一代到下一代的忠实传递。它促进了DNA复制、重组和修复之间的相互作用，并提供了挽救因模板DNA上或内部的损伤而停滞的复制叉的方法。对RecG蛋白（DNA和RNA解旋酶超家族2的成员）的遗传、生化和结构研究揭示了这种相互转化可能是如何被催化的。我们描述了单个RecG分子如何靶向分支DNA结构，并使单链双链臂移位以驱动霍利迪连接体的分支迁移，将复制叉和霍利迪连接体结构相互转化，并从DNA末端重组过程中形成的D环中置换入侵链。我们提供的遗传学证据表明，后一种活性可能为DNA双链断裂的修复提供一条有效的途径，避免交叉，从而促进细胞分裂时的染色体分离。
