Courcelle Justin, Donaldson Janet R, Chow Kin-Hoe, Courcelle Charmain T
Department of Biological Sciences, Box GY, Mississippi State University, Mississippi State, MS 39762, USA.
Science. 2003 Feb 14;299(5609):1064-7. doi: 10.1126/science.1081328. Epub 2003 Jan 23.
DNA lesions that block replication are a primary cause of rearrangements, mutations, and lethality in all cells. After ultraviolet (UV)-induced DNA damage in Escherichia coli, replication recovery requires RecA and several other recF pathway proteins. To characterize the mechanism by which lesion-blocked replication forks recover, we used two-dimensional agarose gel electrophoresis to show that replication-blocking DNA lesions induce a transient reversal of the replication fork in vivo. The reversed replication fork intermediate is stabilized by RecA and RecF and is degraded by the RecQ-RecJ helicase-nuclease when these proteins are absent. We propose that fork regression allows repair enzymes to gain access to the replication-blocking lesion, allowing processive replication to resume once the blocking lesion is removed.
阻碍复制的DNA损伤是所有细胞中重排、突变和致死的主要原因。在大肠杆菌受到紫外线(UV)诱导的DNA损伤后,复制恢复需要RecA和其他几种recF途径蛋白。为了阐明损伤阻碍的复制叉恢复机制,我们使用二维琼脂糖凝胶电泳表明,阻碍复制的DNA损伤在体内诱导复制叉的短暂逆转。逆转的复制叉中间体由RecA和RecF稳定,当这些蛋白质不存在时,由RecQ-RecJ解旋酶-核酸酶降解。我们提出,叉回归允许修复酶接触阻碍复制的损伤,一旦阻碍损伤被去除,就允许进行性复制恢复。