Jackson Brian R, Noerenberg Marko, Whitehouse Adrian
School of Molecular and Cellular Biology and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, United Kingdom.
PLoS Pathog. 2014 May 1;10(5):e1004098. doi: 10.1371/journal.ppat.1004098. eCollection 2014 May.
Kaposi's sarcoma-associated herpesvirus (KSHV) is an oncogenic herpesvirus associated with multiple AIDS-related malignancies. Like other herpesviruses, KSHV has a biphasic life cycle and both the lytic and latent phases are required for tumorigenesis. Evidence suggests that KSHV lytic replication can cause genome instability in KSHV-infected cells, although no mechanism has thus far been described. A surprising link has recently been suggested between mRNA export, genome instability and cancer development. Notably, aberrations in the cellular transcription and export complex (hTREX) proteins have been identified in high-grade tumours and these defects contribute to genome instability. We have previously shown that the lytically expressed KSHV ORF57 protein interacts with the complete hTREX complex; therefore, we investigated the possible intriguing link between ORF57, hTREX and KSHV-induced genome instability. Herein, we show that lytically active KSHV infected cells induce a DNA damage response and, importantly, we demonstrate directly that this is due to DNA strand breaks. Furthermore, we show that sequestration of the hTREX complex by the KSHV ORF57 protein leads to this double strand break response and significant DNA damage. Moreover, we describe a novel mechanism showing that the genetic instability observed is a consequence of R-loop formation. Importantly, the link between hTREX sequestration and DNA damage may be a common feature in herpesvirus infection, as a similar phenotype was observed with the herpes simplex virus 1 (HSV-1) ICP27 protein. Our data provide a model of R-loop induced DNA damage in KSHV infected cells and describes a novel system for studying genome instability caused by aberrant hTREX.
卡波西肉瘤相关疱疹病毒（KSHV）是一种与多种艾滋病相关恶性肿瘤有关的致癌性疱疹病毒。与其他疱疹病毒一样，KSHV具有双相生命周期，其裂解期和潜伏期对于肿瘤发生都是必需的。有证据表明，KSHV的裂解复制可导致KSHV感染细胞中的基因组不稳定，尽管迄今为止尚未描述其机制。最近有人提出了mRNA输出、基因组不稳定与癌症发展之间令人惊讶的联系。值得注意的是，在高级别肿瘤中已发现细胞转录和输出复合体（hTREX）蛋白的异常，这些缺陷会导致基因组不稳定。我们之前已经表明，裂解表达的KSHV ORF57蛋白与完整的hTREX复合体相互作用；因此，我们研究了ORF57、hTREX与KSHV诱导的基因组不稳定之间可能存在的有趣联系。在此，我们表明具有裂解活性的KSHV感染细胞会引发DNA损伤反应，重要的是，我们直接证明这是由于DNA链断裂所致。此外，我们表明KSHV ORF57蛋白对hTREX复合体的隔离导致了这种双链断裂反应和显著的DNA损伤。而且，我们描述了一种新机制，表明观察到的基因不稳定是R环形成的结果。重要的是，hTREX隔离与DNA损伤之间的联系可能是疱疹病毒感染的一个共同特征，因为在单纯疱疹病毒1（HSV-1）ICP27蛋白中也观察到了类似的表型。我们的数据提供了一个KSHV感染细胞中R环诱导DNA损伤的模型，并描述了一个研究由异常hTREX引起的基因组不稳定的新系统。
