ASSOCIATION OF A M(R)-90,000 PHOSPHOPROTEIN WITH PROTEIN-KINASE PKR IN CELLS EXHIBITING ENHANCED PHOSPHORYLATION OF TRANSLATION INITIATION-FACTOR EIF-2-ALPHA AND PREMATURE SHUTOFF OF PROTEIN-SYNTHESIS AFTER INFECTION WITH GAMMA(1)34.5(-) MUTANTS OF HERPES-SIMPLEX-VIRUS-1
ASSOCIATION OF A M(R)-90,000 PHOSPHOPROTEIN WITH PROTEIN-KINASE PKR IN CELLS EXHIBITING ENHANCED PHOSPHORYLATION OF TRANSLATION INITIATION-FACTOR EIF-2-ALPHA AND PREMATURE SHUTOFF OF PROTEIN-SYNTHESIS AFTER INFECTION WITH GAMMA(1)34.5(-) MUTANTS OF HERPES-SIMPLEX-VIRUS-1
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DOI：
10.1073/pnas.92.23.10516
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发表时间：
1995-11-07
影响因子：
11.1
通讯作者：
ROIZMAN, B
中科院分区：
文献类型：
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作者：
CHOU, J;CHEN, JJ;ROIZMAN, B
单纯疱疹病毒的 gamma(I)34.5 基因编码的蛋白质可以防止人类细胞中因病毒 DNA 合成开始相关的应激而过早停止蛋白质合成。蛋白质的羧基末端对于该功能至关重要。该报告表明蛋白质合成的停止并不是由于 mRNA 降解，因为来自野生型或 γ(I)34.5(-) 病毒感染细胞的 mRNA 指导蛋白质合成。对翻译起始因子eIF-2的翻译后修饰的分析表明：(i)eIF-2α被γ(I)34.5(-)病毒感染的细胞的核糖体富集部分中存在的激酶选择性地磷酸化。 (ii) 内源性 eIF-2 α 在感染 γ(I)34.5(-) 病毒或缺乏 γ(I)34.5 基因 3' 编码结构域的病毒的细胞中完全磷酸化，但在模拟感染或野生型病毒感染的细胞中未磷酸化，(iii) PKR 激酶的免疫沉淀物负责通过 eIF-2 α 磷酸化来调节某些细胞的蛋白质合成，产生了多种磷酸化多肽。特别重要的是两个观察结果，首先，相对于模拟感染细胞中的水平，所有感染细胞中 PKR 激酶的磷酸化均升高。其次，感染γ(I)34.5(-)病毒或缺乏γ(I)34.5(-)基因3'编码域的病毒的细胞裂解物的沉淀物含有额外的标记的M(r) 90,000 (p90)磷蛋白。这种磷蛋白仅以痕量存在于感染野生型病毒或缺乏 γ(I)34.5 5' 结构域部分的突变体的细胞的免疫沉淀物中。我们得出结论，在缺少 gamma(I)34.5 蛋白的情况下，PKR 激酶与 p90 磷蛋白复合，并通过翻译起始因子 eIF-2 的 α 亚基磷酸化来关闭蛋白质合成。
The protein encoded by the gamma(I)34.5 gene of herpes simplex virus precludes premature shutoff of protein synthesis in human cells triggered by stress associated with onset of viral DNA synthesis. The carboxyl terminus of the protein is essential for this function. This report indicates that the shutoff of protein synthesis is not due to mRNA degradation because mRNA from wild-type or gamma(I)34.5(-) virus-infected cells directs protein synthesis. Analyses of the posttranslational modifications of translation initiation factor eIF-2 showed the following: (i) eIF-2 alpha was selectively phosphorylated by a kinase present in ribosome-enriched fraction of cells infected with gamma(I)34.5(-) virus. (ii) Endogenous eIF-2 alpha was totally phosphorylated in cells infected with gamma(I)34.5(-) virus or a virus lacking the 3' coding domain of the gamma(I)34.5 gene but was not phosphorylated in mock-infected or wild-type virus-infected cells, (iii) Immune precipitates of the PKR kinase that is responsible for regulation of protein synthesis of some cells by phosphorylation of eIF-2 alpha yielded several phosphorylated polypeptides. Of particular significance were two observations, First, phosphorylation of PKR kinase was elevated in all infected cells relative to the levels in mock-infected cells. Second, the precipitates from lysates of cells infected with gamma(I)34.5(-) virus or a virus lacking the 3' coding domain of the gamma(I)34.5(-) gene contained an additional labeled phosphoprotein of M(r) 90,000 (p90). This phosphoprotein was present in only trace amounts in the immunoprecipitate from cells infected with wild-type virus or mutants lacking a portion of the 5' domain of gamma(I)34.5. We conclude that in the absence of gamma(I)34.5 protein, PKR kinase complexes with the p90 phosphoprotein and shuts off protein synthesis by phosphorylation of the alpha subunit of translation initiation factor eIF-2.