Identification of the Essential Role of Viral Bcl-2 for Kaposi's Sarcoma-Associated Herpesvirus Lytic Replication
Identification of the Essential Role of Viral Bcl-2 for Kaposi's Sarcoma-Associated Herpesvirus Lytic Replication
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DOI：
10.1128/jvi.00102-15
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发表时间：
2015-05-01
影响因子：
5.4
通讯作者：
Jung, Jae U.
中科院分区：
文献类型：
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作者：
Liang, Qiming;Chang, Brian;Jung, Jae U.
卡波西肉瘤相关疱疹病毒 (KSHV) 通过靶向其信号转导的每个步骤来严格抑制自噬，从而逃避宿主防御：通过病毒 Bcl-2 (vBcl-2) 进行囊泡成核，通过病毒 FLIP (vFLIP) 进行囊泡伸长，通过 K7 进行囊泡成熟。通过探索 KSHV 自噬调节基因的作用，我们令人惊讶地发现，vBcl-2 对于 KSHV 裂解性复制至关重要，而 vFLIP 和 K7 则是可有可无的。从 KSHV 基因组中敲除 vBcl-2 会导致 mRNA 和蛋白质水平的裂解基因表达降低、病毒 DNA 拷贝数降低，从而导致后代感染性病毒数量急剧减少，如随附文章中所述（A. Gelgor、I. Kalt、S. Bergson、K. F. Brulois、J. U. Jung 和 R. Sarid，J Virol 89： 5298-5307，2015）。更重要的是，KSHV 裂解复制不需要 vBcl-2 的抗凋亡和抗自噬功能。通过全面的诱变分析，我们发现 vBcl-2 的谷氨酸 14 (E-14) 对于 KSHV 裂解复制至关重要。将 E-14 突变为丙氨酸完全阻断了 KSHV 裂解性复制，但对 vBcl-2 的抗凋亡和抗自噬功能影响很小或没有影响。我们的研究表明，vBcl-2 具有至少三个重要且基因上可分离的功能，可调节细胞信号传导和病毒生命周期。重要性本研究首次表明，vBcl-2 对于 KSHV 裂解复制至关重要。去除 vBcl-2 基因会导致 KSHV 裂解基因表达水平降低，病毒 DNA 复制受损，从而导致后代产量水平急剧下降。更重要的是，vBcl-2在KSHV裂解复制中的作用在基因上与其抗凋亡和抗自噬功能是分离的，这表明KSHV Bcl-2在病毒裂解复制中具有新的功能。
Kaposi's sarcoma-associated herpesvirus (KSHV) evades host defenses through tight suppression of autophagy by targeting each step of its signal transduction: by viral Bcl-2 (vBcl-2) in vesicle nucleation, by viral FLIP (vFLIP) in vesicle elongation, and by K7 in vesicle maturation. By exploring the roles of KSHV autophagy-modulating genes, we found, surprisingly, that vBcl-2 is essential for KSHV lytic replication, whereas vFLIP and K7 are dispensable. Knocking out vBcl-2 from the KSHV genome resulted in decreased lytic gene expression at the mRNA and protein levels, a lower viral DNA copy number, and, consequently, a dramatic reduction in the amount of progeny infectious viruses, as also described in the accompanying article (A. Gelgor, I. Kalt, S. Bergson, K. F. Brulois, J. U. Jung, and R. Sarid, J Virol 89: 5298-5307, 2015). More importantly, the antiapoptotic and antiautophagic functions of vBcl-2 were not required for KSHV lytic replication. Using a comprehensive mutagenesis analysis, we identified that glutamic acid 14 (E-14) of vBcl-2 is critical for KSHV lytic replication. Mutating E-14 to alanine totally blocked KSHV lytic replication but showed little or no effect on the antiapoptotic and antiautophagic functions of vBcl-2. Our study indicates that vBcl-2 harbors at least three important and genetically separable functions to modulate both cellular signaling and the virus life cycle.IMPORTANCEThe present study shows for the first time that vBcl-2 is essential for KSHV lytic replication. Removal of the vBcl-2 gene results in a lower level of KSHV lytic gene expression, impaired viral DNA replication, and consequently, a dramatic reduction in the level of progeny production. More importantly, the role of vBcl-2 in KSHV lytic replication is genetically separated from its antiapoptotic and antiautophagic functions, suggesting that the KSHV Bcl-2 carries a novel function in viral lytic replication.