Taddeo Brunella, Luo Ting Rong, Zhang Weiran, Roizman Bernard
The Marjorie B. Kovler Viral Oncology Laboratories, University of Chicago, 910 East 58th Street, Chicago, IL 60637, USA.
Proc Natl Acad Sci U S A. 2003 Oct 14;100(21):12408-13. doi: 10.1073/pnas.2034952100. Epub 2003 Oct 6.
Microarray data reported elsewhere indicated that herpes simplex virus 1 induces the up-regulation of nuclear factor kappaB (NF-kappaB)-regulated genes, including that of its inhibitor, IkappaBalpha, consistent with the reports that wild-type virus induces the activation of NF-kappaB. In this report we show that activation of NF-kappaB in infected cells is linked to the activation of protein kinase R (PKR). Specifically: (i) PKR is activated in infected cells although the effects of the activated enzyme on protein synthesis are negated by the viral gene gamma134.5, which encodes a protein phosphatase 1alpha accessory factor that enables the dephosphorylation of the alpha subunit of eukaryotic translation initiation factor 2. NF-kappaB is activated in wild-type murine embryonic fibroblasts but not in related PKR-null cells. (ii) In cells infected with a replication-competent Deltagamma134.5 mutant (R5104), but carrying a US11 gene expressed early in infection, eukaryotic translation initiation factor 2alpha is not phosphorylated, and in in vitro assays, PKR bound to the US11 protein is not phosphorylated on subsequent addition of double-stranded RNA. Here we report that this mutant does not activate PKR, has no effect on the accumulation of IkappaBalpha, and does not cause the translocation of NF-kappaB in infected cells. (iii) One hypothesis advanced for the activation of NF-kappaB is that it blocks apoptosis induced by viral gene products. The replication-competent R5104 mutant does not induce the programmed cell's death. We conclude that in herpes simplex virus 1-infected cells, activation of NF-kappaB depends on activation of PKR and that NF-kappaB is not required to block apoptosis in productively infected cells.
其他地方报道的微阵列数据表明，单纯疱疹病毒1可诱导核因子κB（NF-κB）调控基因的上调，包括其抑制剂IκBα的基因，这与野生型病毒诱导NF-κB激活的报道一致。在本报告中，我们表明感染细胞中NF-κB的激活与蛋白激酶R（PKR）的激活有关。具体如下：（i）PKR在感染细胞中被激活，尽管激活的酶对蛋白质合成的影响被病毒基因γ134.5抵消，该基因编码一种蛋白磷酸酶1α辅助因子，可使真核翻译起始因子2的α亚基去磷酸化。NF-κB在野生型小鼠胚胎成纤维细胞中被激活，但在相关的PKR基因缺失细胞中未被激活。（ii）在感染了具有复制能力的Δγ134.5突变体（R5104）但携带感染早期表达的US11基因的细胞中，真核翻译起始因子2α未被磷酸化，并且在体外试验中，与US11蛋白结合的PKR在随后添加双链RNA时未被磷酸化。我们在此报告，该突变体不激活PKR，对IκBα的积累没有影响，并且在感染细胞中不会导致NF-κB的易位。（iii）关于NF-κB激活提出的一个假说是，它可阻断病毒基因产物诱导的细胞凋亡。具有复制能力的R5104突变体不会诱导程序性细胞死亡。我们得出结论，在单纯疱疹病毒1感染的细胞中，NF-κB的激活依赖于PKR的激活，并且在高效感染的细胞中，NF-κB不是阻断细胞凋亡所必需的。
