Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America.
PLoS Pathog. 2011 May;7(5):e1001342. doi: 10.1371/journal.ppat.1001342. Epub 2011 May 12.
DNA damage resulting from intrinsic or extrinsic sources activates DNA damage responses (DDRs) centered on protein kinase signaling cascades. The usual consequences of inducing DDRs include the activation of cell cycle checkpoints together with repair of the damaged DNA or induction of apoptosis. Many DNA viruses elicit host DDRs during infection and some viruses require the DDR for efficient replication. However, the mechanism by which DDRs are activated by viral infection is poorly understood. Human cytomegalovirus (HCMV) infection induces a DDR centered on the activation of ataxia telangiectasia mutated (ATM) protein kinase. Here we show that HCMV replication is compromised in cells with inactivated or depleted ATM and that ATM is essential for the host DDR early during infection. Likewise, a downstream target of ATM phosphorylation, H2AX, also contributes to viral replication. The ATM-dependent DDR is detected as discrete, nuclear γH2AX foci early in infection and can be activated by IE proteins. By 24 hpi, γH2AX is observed primarily in HCMV DNA replication compartments. We identified a role for the E2F1 transcription factor in mediating this DDR and viral replication. E2F1, but not E2F2 or E2F3, promotes the accumulation of γH2AX during HCMV infection or IE protein expression. Moreover, E2F1 expression, but not the expression of E2F2 or E2F3, is required for efficient HCMV replication. These results reveal a novel role for E2F1 in mediating an ATM-dependent DDR that contributes to viral replication. Given that E2F activity is often deregulated by infection with DNA viruses, these observations raise the possibility that an E2F1-mediated mechanism of DDR activation may be conserved among DNA viruses.
DNA 损伤源自内在或外在的来源，激活了以蛋白激酶信号级联为中心的 DNA 损伤反应 (DDR)。诱导 DDR 的常见后果包括细胞周期检查点的激活，以及受损 DNA 的修复或细胞凋亡的诱导。许多 DNA 病毒在感染过程中引发宿主 DDR，有些病毒需要 DDR 才能有效复制。然而，病毒感染激活 DDR 的机制还不清楚。人巨细胞病毒 (HCMV) 感染诱导以共济失调毛细血管扩张症突变 (ATM) 蛋白激酶激活为中心的 DDR。在这里，我们表明失活或耗尽 ATM 的细胞中 HCMV 复制受损，ATM 是感染早期宿主 DDR 的必需条件。同样，ATM 磷酸化的下游靶标 H2AX 也有助于病毒复制。ATM 依赖性 DDR 在感染早期以离散的核 γH2AX 焦点的形式被检测到，并且可以被 IE 蛋白激活。在 24 hpi 时，γH2AX 主要在 HCMV DNA 复制隔间中观察到。我们确定了 E2F1 转录因子在介导这种 DDR 和病毒复制中的作用。E2F1，但不是 E2F2 或 E2F3，在 HCMV 感染或 IE 蛋白表达期间促进 γH2AX 的积累。此外，E2F1 的表达，而不是 E2F2 或 E2F3 的表达，是 HCMV 复制所必需的。这些结果揭示了 E2F1 在介导 ATM 依赖性 DDR 中的新作用，该 DDR 有助于病毒复制。鉴于 E2F 活性通常因感染 DNA 病毒而失调，这些观察结果提出了这样一种可能性，即 DDR 激活的 E2F1 介导机制可能在 DNA 病毒中是保守的。
