ATR/Chk1 pathway is essential for resumption of DNA synthesis and cell survival in UV-irradiated XP variant cells
ATR/Chk1 pathway is essential for resumption of DNA synthesis and cell survival in UV-irradiated XP variant cells
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DOI：
10.1093/hmg/ddq046
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发表时间：
2010-05-01
影响因子：
3.5
通讯作者：
Kannouche, Patricia L.
中科院分区：
文献类型：
--
作者：
Despras, Emmanuelle;Daboussi, Fayza;Kannouche, Patricia L.
DNA 聚合酶 eta (pol eta) 执行跨损伤合成紫外线 (UV) 光产物，并且在易患癌症的着色性干皮病变体 (XP-V) 综合征中缺乏。 XP-V 细胞对紫外线的轻微敏感性因低浓度咖啡因而显着增强。到目前为止，这一特征的生物学解释仍然难以捉摸。通过DNA梳理，我们发现跨损伤合成缺陷会导致人类细胞中活跃复制叉的数量大幅减少，并且停滞叉的比例很高，这与芽殖酵母形成鲜明对比。此外，在受辐射的 XP-V 细胞中复制过程中会形成大量的单链 DNA 区域，导致低 UVC 剂量后 ATR/Chk1 通路过度激活。照射后添加低浓度咖啡因虽然无法有效恢复 S 期进展，但会显着降低 XP-V 细胞中 Chk1 的激活并消除 DNA 合成。虽然 UCN-01 抑制 Chk1 活性可以防止野生型细胞中 UVC 诱导的 S 期延迟，但它会通过增加叉停顿而加剧 XP-V 细胞中的复制缺陷。因此，UCN-01 可以像咖啡因一样使 XP-V 细胞对 UVC 敏感。我们的研究结果表明，pol eta 作用于停滞的分叉以恢复其进展，从而防止在低 UVC 剂量后需要有效的复制检查点。在缺乏 pol eta 的情况下，Chk1 激酶对于通过替代途径（通过叉稳定）恢复复制至关重要。
DNA polymerase eta (pol eta) performs translesion synthesis past ultraviolet (UV) photoproducts and is deficient in cancer-prone xeroderma pigmentosum variant (XP-V) syndrome. The slight sensitivity of XP-V cells to UV is dramatically enhanced by low concentrations of caffeine. So far, the biological explanation for this feature remains elusive. Using DNA combing, we showed that translesion synthesis defect leads to a strong reduction in the number of active replication forks and a high proportion of stalled forks in human cells, which contrasts with budding yeast. Moreover, extensive regions of single-strand DNA are formed during replication in irradiated XP-V cells, leading to an over-activation of ATR/Chk1 pathway after low UVC doses. Addition of a low concentration of caffeine post-irradiation, although inefficient to restore S-phase progression, significantly decreases Chk1 activation and abrogates DNA synthesis in XP-V cells. While inhibition of Chk1 activity by UCN-01 prevents UVC-induced S-phase delay in wild-type cells, it aggravates replication defect in XP-V cells by increasing fork stalling. Consequently, UCN-01 sensitizes XP-V cells to UVC as caffeine does. Our findings indicate that pol eta acts at stalled forks to resume their progression, preventing the requirement for efficient replication checkpoint after low UVC doses. In the absence of pol eta, Chk1 kinase becomes essential for replication resumption by alternative pathways, via fork stabilization.