Institute of Genetics, Biological Research Center, Hungarian Academy of Sciences, Szeged, Temesvari krt.62, H-6726, Hungary. .
Mol Cell Biol. 2010 Feb;30(3):684-93. doi: 10.1128/MCB.00863-09. Epub 2009 Nov 30.
Unrepaired DNA lesions can block the progression of the replication fork, leading to genomic instability and cancer in higher-order eukaryotes. In Saccharomyces cerevisiae, replication through DNA lesions can be mediated by translesion synthesis DNA polymerases, leading to error-free or error-prone damage bypass, or by Rad5-mediated template switching to the sister chromatid that is inherently error free. While translesion synthesis pathways are highly conserved from yeast to humans, very little is known of a Rad5-like pathway in human cells. Here we show that a human homologue of Rad5, HLTF, can facilitate fork regression and has a role in replication of damaged DNA. We found that HLTF is able to reverse model replication forks, a process which depends on its double-stranded DNA translocase activity. Furthermore, from analysis of isolated dually labeled chromosomal fibers, we demonstrate that in vivo, HLTF promotes the restart of replication forks blocked at DNA lesions. These findings suggest that HLTF can promote error-free replication of damaged DNA and support a role for HLTF in preventing mutagenesis and carcinogenesis, providing thereby for its potential tumor suppressor role.
未修复的 DNA 损伤可阻碍复制叉的前进，导致真核生物基因组不稳定和癌症。在酿酒酵母中，DNA 损伤部位的复制可通过跨损伤合成 DNA 聚合酶介导，导致无差错或易错损伤跨越，或通过 Rad5 介导的模板切换到姐妹染色单体（固有无差错）。虽然跨损伤合成途径在从酵母到人高度保守，但对人类细胞中的 Rad5 样途径知之甚少。在这里，我们证明了 Rad5 的人类同源物 HLTF 可以促进叉回归，并在受损 DNA 的复制中发挥作用。我们发现 HLTF 能够逆转模型复制叉，这一过程依赖于其双链 DNA 转位酶活性。此外，通过对分离的双重标记染色体纤维的分析，我们证明在体内，HLTF 促进了在 DNA 损伤处受阻的复制叉的重新启动。这些发现表明，HLTF 可以促进受损 DNA 的无差错复制，并支持 HLTF 在防止诱变和致癌中的作用，从而为其提供潜在的肿瘤抑制作用。
