Institute of Molecular Genetics IGM-CNR, via Abbiategrasso 207, I-27100 Pavia, Italy.
Nucleic Acids Res. 2013 Jan 7;41(1):229-41. doi: 10.1093/nar/gks1016. Epub 2012 Oct 30.
Human DNA polymerase (pol) λ functions in base excision repair and non-homologous end joining. We have previously shown that DNA pol λ is involved in accurate bypass of the two frequent oxidative lesions, 7,8-dihydro-8-oxoguanine and 1,2-dihydro-2-oxoadenine during the S phase. However, nothing is known so far about the relationship of DNA pol λ with the S phase DNA damage response checkpoint. Here, we show that a knockdown of DNA pol λ, but not of its close homologue DNA pol β, results in replication fork stress and activates the S phase checkpoint, slowing S phase progression in different human cancer cell lines. We furthermore show that DNA pol λ protects cells from oxidative DNA damage and also functions in rescuing stalled replication forks. Its absence becomes lethal for a cell when a functional checkpoint is missing, suggesting a DNA synthesis deficiency. Our results provide the first evidence, to our knowledge, that DNA pol λ is required for cell cycle progression and is functionally connected to the S phase DNA damage response machinery in cancer cells.
人类 DNA 聚合酶（pol）λ在碱基切除修复和非同源末端连接中发挥作用。我们之前已经表明，DNA pol λ 参与了在 S 期准确绕过两种常见的氧化损伤，即 7,8-二氢-8-氧鸟嘌呤和 1,2-二氢-2-氧腺嘌呤。然而，目前尚不清楚 DNA pol λ 与 S 期 DNA 损伤反应检查点之间的关系。在这里，我们表明，DNA pol λ 的敲低，而不是其密切同源物 DNA pol β 的敲低，会导致复制叉压力并激活 S 期检查点，从而减缓不同人癌细胞系中 S 期的进程。我们还表明，DNA pol λ 可保护细胞免受氧化 DNA 损伤，还可在挽救停滞的复制叉方面发挥作用。当缺少功能正常的检查点时，其缺失对细胞是致命的，这表明 DNA 合成缺陷。我们的研究结果首次提供了证据，据我们所知，DNA pol λ 是细胞周期进程所必需的，并且在癌细胞中与 S 期 DNA 损伤反应机制在功能上相关。
