The Adenovirus E4orf4 Protein Provides a Novel Mechanism for Inhibition of the DNA Damage Response.
The Adenovirus E4orf4 Protein Provides a Novel Mechanism for Inhibition of the DNA Damage Response.
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DOI：
10.1371/journal.ppat.1005420
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发表时间：
2016-02
期刊：
影响因子：
6.7
通讯作者：
Kleinberger T
中科院分区：
文献类型：
--
作者：
Brestovitsky A;Nebenzahl-Sharon K;Kechker P;Sharf R;Kleinberger T
DNA损伤反应（DDR）是一系列途径的集合，旨在检测DNA损伤并向细胞周期检查点和修复机制发出其存在的信号，允许细胞暂停并修复损伤，或者如果损伤太严重，则触发凋亡或衰老。各种DDR分支由磷脂酰肌醇3-激酶样蛋白激酶家族的激酶调节，包括共济失调-毛细血管扩张突变（ATM）和ATM-和Rad 3-相关（ATR）。DNA病毒的复制中间体和线性双链基因组被细胞视为DNA损伤并激活DDR。如果允许操作，DDR将刺激病毒基因组的连接并抑制病毒复制。为了防止这种结果，许多DNA病毒进化出限制DDR的方法。作为其对DDR的攻击的一部分，腺病毒利用各种病毒蛋白来引起DDR蛋白的降解并将MRN损伤传感器隔离在病毒复制中心之外。在这里，我们发现腺病毒进化出另一种新的机制来抑制DDR。E4 orf 4蛋白与其细胞伴侣PP 2A一起减少病毒感染细胞和用DNA损伤药物处理的细胞中ATM和ATR底物的磷酸化，并导致药物处理细胞中受损DNA的积累。ATM和ATR对于E4 orf 4抑制它们的信号传导通路不是相互需要的。ATM和ATR缺陷以及E4 orf 4表达增强感染效率。此外，先前报道的E4 orf 4在单独表达时诱导癌症特异性细胞死亡，使细胞对亚致死浓度的DNA损伤药物的杀伤敏感，这可能是因为它抑制DNA损伤修复。这些发现为E4 orf 4诱导的细胞死亡的癌症特异性提供了一种解释，因为许多癌症具有DDR缺陷，导致对剩余的完整DDR途径的依赖增加，并且对DDR抑制剂如E4 orf 4的敏感性增强。因此，E4 orf 4对DDR的抑制有助于腺病毒复制的效率和E4 orf 4杀死癌细胞的能力。细胞DNA损伤反应（DDR）网络将复制病毒DNA基因组的存在解释为DNA损伤，并努力修复它，从而抑制病毒复制。许多DNA病毒，包括腺病毒，进化出抑制DDR的机制，从而提高病毒复制的效率。在这项研究中，我们确定了腺病毒抑制DDR的新机制。病毒E4 orf 4蛋白及其细胞伴侣PP 2A磷酸酶通过减少属于不同DDR分支的蛋白质的磷酸化来抑制损伤信号传导。因此，E4 orf 4导致细胞中DNA损伤的积累。DDR调节剂ATM和ATR的抑制以及E4 orf 4的表达增强了感染效率。此外，E4 orf 4使细胞对亚致死浓度的DNA损伤药物的杀伤敏感，可能是因为它抑制DNA修复。这些发现可以为先前报道的E4 orf 4诱导癌症特异性细胞死亡的能力提供一种解释，因为许多癌症具有DDR缺陷，导致它们对剩余的完整DDR途径的依赖增加，并且对DDR抑制剂如E4 orf 4的敏感性增强。因此，E4 orf 4对DDR的抑制有助于病毒复制效率和E4 orf 4诱导的癌细胞杀伤。
The DNA damage response (DDR) is a conglomerate of pathways designed to detect DNA damage and signal its presence to cell cycle checkpoints and to the repair machinery, allowing the cell to pause and mend the damage, or if the damage is too severe, to trigger apoptosis or senescence. Various DDR branches are regulated by kinases of the phosphatidylinositol 3-kinase-like protein kinase family, including ataxia-telangiectasia mutated (ATM) and ATM- and Rad3-related (ATR). Replication intermediates and linear double-stranded genomes of DNA viruses are perceived by the cell as DNA damage and activate the DDR. If allowed to operate, the DDR will stimulate ligation of viral genomes and will inhibit virus replication. To prevent this outcome, many DNA viruses evolved ways to limit the DDR. As part of its attack on the DDR, adenovirus utilizes various viral proteins to cause degradation of DDR proteins and to sequester the MRN damage sensor outside virus replication centers. Here we show that adenovirus evolved yet another novel mechanism to inhibit the DDR. The E4orf4 protein, together with its cellular partner PP2A, reduces phosphorylation of ATM and ATR substrates in virus-infected cells and in cells treated with DNA damaging drugs, and causes accumulation of damaged DNA in the drug-treated cells. ATM and ATR are not mutually required for inhibition of their signaling pathways by E4orf4. ATM and ATR deficiency as well as E4orf4 expression enhance infection efficiency. Furthermore, E4orf4, previously reported to induce cancer-specific cell death when expressed alone, sensitizes cells to killing by sub-lethal concentrations of DNA damaging drugs, likely because it inhibits DNA damage repair. These findings provide one explanation for the cancer-specificity of E4orf4-induced cell death as many cancers have DDR deficiencies leading to increased reliance on the remaining intact DDR pathways and to enhanced susceptibility to DDR inhibitors such as E4orf4. Thus DDR inhibition by E4orf4 contributes both to the efficiency of adenovirus replication and to the ability of E4orf4 to kill cancer cells. The cellular DNA damage response (DDR) network interprets the presence of replicating viral DNA genomes as DNA damage and strives to repair it, leading to inhibition of virus replication. Many DNA viruses, including adenovirus, evolved mechanisms to inhibit the DDR, thus increasing the efficiency of virus replication. In this study we identify a novel mechanism used by adenovirus to inhibit the DDR. The viral E4orf4 protein, together with its cellular partner, the PP2A phosphatase, inhibits damage signaling by reducing phosphorylation of proteins belonging to different DDR branches. As a result, E4orf4 causes accumulation of DNA damage in the cells. Inhibition of the DDR regulators ATM and ATR, as well as expression of E4orf4, enhances infection efficiency. Moreover, E4orf4 sensitizes cells to killing by sub-lethal concentrations of DNA damaging drugs, likely because it inhibits DNA repair. These findings could provide one explanation for the previously reported ability of E4orf4 to induce cancer-specific cell death, as many cancers have DDR deficiencies leading to their increased reliance on the remaining intact DDR pathways and to enhanced susceptibility to DDR inhibitors such as E4orf4. Thus, inhibition of the DDR by E4orf4 contributes both to viral replication efficiency and to E4orf4-induced cancer cell killing.