Inhibition of Human Cytomegalovirus Immediate-Early Gene Expression by Cyclin A2-Dependent Kinase Activity
Inhibition of Human Cytomegalovirus Immediate-Early Gene Expression by Cyclin A2-Dependent Kinase Activity
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DOI：
10.1128/jvi.07181-11
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发表时间：
2012-06
影响因子：
5.4
通讯作者：
Jennifer D. Oduro;Ralf Uecker;C. Hagemeier;Lüder Wiebusch
中科院分区：
文献类型：
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作者：
Jennifer D. Oduro;Ralf Uecker;C. Hagemeier;Lüder Wiebusch
摘要人巨细胞病毒(HCMV)仅在细胞分裂周期的G0/G1期开始其裂解复制周期。S/G2细胞可被感染，但可阻断即刻早期(IE)基因的表达。这一障碍可以通过抑制细胞周期蛋白依赖性蛋白激酶(CDK)来克服，这表明细胞周期蛋白A2是唯一具有S/G2特异性活性的细胞周期蛋白，可能是病毒基因表达的负调控因子。为了直接验证这一假设，我们产生了一种HCMV允许的胶质母细胞瘤细胞系的衍生物，它以一种结构性的、细胞周期无关的方式表达细胞周期蛋白A2。我们证明，即使在G1中适度的细胞周期蛋白A2的过度表达也足以严重破坏高多样性感染后的HCMV复制周期。这种负面影响包括对IE基因转录的强烈但短暂的抑制，以及更持续的IE mRNA加工改变，导致病毒早期基因表达的关键反式激活因子UL37和IE2水平降低。细胞周期蛋白A2过表达细胞表现出强烈的延迟病毒早期和晚期基因表达以及病毒复制的作用。所有的作用都依赖于CDK活性，因为CDK结合缺陷的Cyclin A2突变体不能干扰HCMV的感染循环。有趣的是，小鼠巨细胞病毒的IE基因的表达不受细胞周期的影响，不受细胞周期蛋白A2的影响。相反，它在感染时上调细胞周期蛋白A2相关的激酶活性。了解细胞周期蛋白A2-CDK在巨细胞病毒特异性作用背后的机制可能会为抗病毒策略提供新的靶点。
ABSTRACT Human cytomegalovirus (HCMV) starts its lytic replication cycle only in the G0/G1 phase of the cell division cycle. S/G2 cells can be infected but block the onset of immediate-early (IE) gene expression. This block can be overcome by inhibition of cyclin-dependent kinases (CDKs), suggesting that cyclin A2, the only cyclin with an S/G2-specific activity profile, may act as a negative regulator of viral gene expression. To directly test this hypothesis, we generated derivatives of an HCMV-permissive glioblastoma cell line that express cyclin A2 in a constitutive, cell cycle-independent manner. We demonstrate that even moderate cyclin A2 overexpression in G1 was sufficient to severely compromise the HCMV replicative cycle after high-multiplicity infection. This negative effect was composed of a strong but transient inhibition of IE gene transcription and a more sustained alteration of IE mRNA processing, resulting in reduced levels of UL37 and IE2, an essential transactivator of viral early gene expression. Consistently, cyclin A2-overexpressing cells showed a strong delay of viral early and late gene expression, as well as virus reproduction. All effects were dependent on CDK activity, as a cyclin A2 mutant deficient in CDK binding was unable to interfere with the HCMV infectious cycle. Interestingly, murine CMV, whose IE gene expression is known to be cell cycle independent, is not affected by cyclin A2. Instead, it upregulates cyclin A2-associated kinase activity upon infection. Understanding the mechanisms behind the HCMV-specific action of cyclin A2-CDK might reveal new targets for antiviral strategies.