Department of Microbiology, Miami University, Oxford, Ohio, USA.
J Virol. 2013 Aug;87(15):8687-96. doi: 10.1128/JVI.00376-13. Epub 2013 Jun 5.
Adenovirus (Ad) mutants that lack early region 4 (E4) are unable to produce the early regulatory proteins that normally inactivate the Mre11/Rad50/Nbs1 (MRN) sensor complex, which is a critical component for the ability of cells to respond to DNA damage. E4 mutant infection therefore activates a DNA damage response, which in turn interferes with a productive viral infection. MRN complex proteins localize to viral DNA replication centers in E4 mutant-infected cells, and this complex is critical for activating the kinases ataxia-telangiectasia mutated (ATM) and ATM and Rad3-related (ATR), which phosphorylate numerous substrates important for DNA repair, cell cycle checkpoint activation, and apoptosis. E4 mutant growth defects are substantially rescued in cells lacking an intact MRN complex. We have assessed the role of the downstream ATM and ATR kinases in several MRN-dependent E4 mutant phenotypes. We did not identify a role for either ATM or ATR in "repair" of E4 mutant genomes to form concatemers. ATR was also not observed to contribute to E4 mutant defects in late protein production. In contrast, the kinase activity of ATM was important for preventing efficient E4 mutant DNA replication and late gene expression. Our results suggest that the MRN complex interferes with E4 mutant DNA replication at least in part through its ability to activate ATM.
腺病毒（Ad）突变体缺乏早期区域 4（E4），无法产生早期调节蛋白，这些蛋白通常会使 Mre11/Rad50/Nbs1（MRN）传感器复合物失活，而该复合物是细胞对 DNA 损伤做出反应的关键组成部分。因此，E4 突变体感染会激活 DNA 损伤反应，从而干扰病毒的有效感染。E4 突变体感染细胞中，MRN 复合物蛋白定位于病毒 DNA 复制中心，该复合物对于激活激酶共济失调毛细血管扩张症突变（ATM）和 ATM 和 Rad3 相关（ATR）至关重要，它们磷酸化许多对 DNA 修复、细胞周期检查点激活和细胞凋亡很重要的底物。在缺乏完整的 MRN 复合物的细胞中，E4 突变体的生长缺陷得到了显著挽救。我们评估了下游 ATM 和 ATR 激酶在几种依赖于 MRN 的 E4 突变体表型中的作用。我们没有发现 ATM 或 ATR 在 E4 突变基因组的“修复”以形成串联体中发挥作用。也没有观察到 ATR 有助于 E4 突变体在晚期蛋白生产中的缺陷。相比之下，ATM 的激酶活性对于防止 E4 突变体的有效 DNA 复制和晚期基因表达很重要。我们的结果表明，MRN 复合物通过激活 ATM 至少部分地干扰 E4 突变体 DNA 复制。
