Human cytomegalovirus evades ZAP detection by suppressing CpG dinucleotides in the major immediate early genes
Human cytomegalovirus evades ZAP detection by suppressing CpG dinucleotides in the major immediate early genes
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人类巨细胞病毒通过抑制主要立即早期基因中的 CpG 二核苷酸来逃避 ZAP 检测
DOI：
10.1101/2020.01.07.897132
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Lin Y
中科院分区：
文献类型：
--
作者：
Lin Y
脊椎动物的RNA和小DNA病毒的基因组显示出显著的CpG二核苷酸频率抑制。牺牲性增加二核苷酸频率导致病毒复制的大幅衰减，表明这些组成的变化可能有助于识别非自身RNA序列。最近，干扰素诱导蛋白ZAP被鉴定为负责通过直接结合和可能的下游靶向降解来感测病毒RNA中的CpG的宿主因子。使用阵列干扰素刺激的基因表达文库筛选，我们确定ZAPS，及其相关因子TRIM25，作为人巨细胞病毒（HCMV）复制的抑制剂。ZAPS和TRIM25的外源表达显著降低了病毒复制，而敲低导致病毒复制增加。HCMV表现出惊人的CpG代表性的异质性模式，在IE1主要立即早期转录本中特异性抑制CpG基序，这在随后表达的基因中是不存在的。我们证明了抑制IE1基因中的CpG二核苷酸可以逃避ZAP的抑制作用。我们发现，急性病毒复制是互斥的高水平的细胞ZAP，可能解释了较高水平的CpG在病毒基因表达后IE1由于ZAP在感染细胞中的压力损失。最后，我们表明，TRIM25调节在HCMV感染和干扰素诱导过程中ZAP短和长亚型之间的选择性剪接，TRIM25的敲低导致ZAPS降低和相应的ZAPL表达增加。这些结果首次表明，ZAP是一种有效的宿主限制因子，对大的DNA病毒和HCMV逃避ZAP检测通过抑制主要立即早期1转录内的CpG二核苷酸。此外，TRIM 25是通过调节可变剪接有效上调干扰素诱导型短ZAP同种型所必需的。
The genomes of RNA and small DNA viruses of vertebrates display significant suppression of CpG dinucleotide frequencies. Artificially increasing dinucleotide frequencies results in substantial attenuation of virus replication, suggesting that these compositional changes may facilitate recognition of non-self RNA sequences. Recently, the interferon inducible protein ZAP, was identified as the host factor responsible for sensing CpG in viral RNA, through direct binding and possibly downstream targeting for degradation. Using an arrayed interferon stimulated gene expression library screen, we identified ZAPS, and its associated factor TRIM25, as inhibitors of human cytomegalovirus (HCMV) replication. Exogenous expression of ZAPS and TRIM25 significantly reduced virus replication while knockdown resulted in increased virus replication. HCMV displays a strikingly heterogeneous pattern of CpG representation with specific suppression of CpG motifs within the IE1 major immediate early transcript which is absent in subsequently expressed genes. We demonstrated that suppression of CpG dinucleotides in the IE1 gene allows evasion of inhibitory effects of ZAP. We show that acute virus replication is mutually exclusive with high levels of cellular ZAP, potentially explaining the higher levels of CpG in viral genes expressed subsequent to IE1 due to the loss of pressure from ZAP in infected cells. Finally, we show that TRIM25 regulates alternative splicing between the ZAP short and long isoforms during HCMV infection and interferon induction, with knockdown of TRIM25 resulting in decreased ZAPS and corresponding increased ZAPL expression. These results demonstrate for the first time that ZAP is a potent host restriction factor against large DNA viruses and that HCMV evades ZAP detection through suppression of CpG dinucleotides within the major immediate early 1 transcript. Furthermore, TRIM25 is required for efficient upregulation of the interferon inducible short isoform of ZAP through regulation of alternative splicing.