Bugreev Dmitry V, Hanaoka Fumio, Mazin Alexander V
Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, Pennsylvania 19102-1192, USA.
Nat Struct Mol Biol. 2007 Aug;14(8):746-53. doi: 10.1038/nsmb1268. Epub 2007 Jul 29.
Double-strand DNA breaks (DSBs) cause cell death and genome instability. Homologous recombination is a major DSB repair pathway that operates by forming joint molecules with homologous DNA sequences, which are used as templates to achieve accurate repair. In eukaryotes, Rad51 protein (RecA homolog) searches for homologous sequences and catalyzes the formation of joint molecules (D-loops). Once joint molecules have been formed, DNA polymerase extends the 3' single-stranded DNA tails of the broken chromosome, restoring the lost information. How joint molecules subsequently dissociate is unknown. We reconstituted DSB repair in vitro using purified human homologous recombination proteins and DNA polymerase eta. We found that Rad54 protein, owing to its ATP-dependent branch-migration activity, can cause dissociation of joint molecules. These results suggest a previously uncharacterized mechanism of DSB repair in which Rad54 branch-migration activity plays an important role.
双链DNA断裂（DSB）会导致细胞死亡和基因组不稳定。同源重组是一种主要的DSB修复途径，其通过与同源DNA序列形成接头分子来发挥作用，这些接头分子被用作模板以实现精确修复。在真核生物中，Rad51蛋白（RecA同源物）寻找同源序列并催化接头分子（D环）的形成。一旦形成接头分子，DNA聚合酶就会延伸断裂染色体的3'单链DNA尾巴，恢复丢失的信息。接头分子随后如何解离尚不清楚。我们使用纯化的人类同源重组蛋白和DNA聚合酶η在体外重建了DSB修复。我们发现，Rad54蛋白由于其依赖ATP的分支迁移活性，可导致接头分子解离。这些结果提示了一种以前未被描述的DSB修复机制，其中Rad54分支迁移活性起着重要作用。
