THE 58-KILODALTON INHIBITOR OF THE INTERFERON-INDUCED DOUBLE-STRANDED RNA-ACTIVATED PROTEIN-KINASE IS A TETRATRICOPEPTIDE REPEAT PROTEIN WITH ONCOGENIC PROPERTIES
THE 58-KILODALTON INHIBITOR OF THE INTERFERON-INDUCED DOUBLE-STRANDED RNA-ACTIVATED PROTEIN-KINASE IS A TETRATRICOPEPTIDE REPEAT PROTEIN WITH ONCOGENIC PROPERTIES
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DOI：
10.1073/pnas.91.10.4278
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发表时间：
1994-05-10
影响因子：
11.1
通讯作者：
KATZE, MG
中科院分区：
文献类型：
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作者：
BARBER, GN;THOMPSON, S;KATZE, MG
干扰素诱导的 RNA 依赖性蛋白激酶 (PKR) 被认为在细胞防御病毒感染方面发挥着重要作用，此外，由于其生长抑制特性，还被认为是一种肿瘤抑制基因。双链 RNA 激活 PKR 会导致真核起始因子 2 (eIF-2 α) 的 α 亚基磷酸化，从而阻碍蛋白质合成起始。为了避免激酶激活的后果，许多病毒已经开发出下调 PKR 的策略。最近，我们报道了一种在流感病毒感染过程中被激活的PKR细胞抑制剂（简称p58）的纯化和表征。随后的克隆和测序表明 p58 是四肽重复 (TPR) 蛋白质家族的成员。为了进一步研究这种 PKR 抑制剂的生理作用，我们用含有受巨细胞病毒早期启动子控制的 p58 cDNA 的真核表达质粒稳定转染 NIH 3T3 细胞。通过利用最近鉴定的 p58 物种特异性单克隆抗体，我们分离出了过表达 p58 的细胞系。这些细胞表现出转变的表型，以更快的速度和更高的饱和密度生长，并表现出不依赖贴壁的生长。最重要的是，用p58过表达细胞接种裸鼠会导致肿瘤的产生。最后，与对照细胞相比，表达 p58 的细胞系中小鼠 PKR 活性和 eIF-2 α 磷酸化的内源水平降低。这些数据综合起来表明 p58 作为癌基因发挥作用，并且该蛋白质诱导恶性转化的一种机制是通过 PKR 的下调以及随后蛋白质合成的失调。
The interferon-induced RNA-dependent protein kinase (PKR) is considered to play an important role in the cellular defense against viral infection and, in addition, has been suggested to be a tumor suppressor gene because of its growth-suppressive properties. Activation of PKR by double-stranded RNAs leads to the phosphorylation of the alpha subunit of eukaryotic initiation factor 2 (eIF-2 alpha) and a resultant block to protein synthesis initiation. To avoid the consequences of kinase activation, many viruses have developed strategies to down-regulate PKR. Recently, we reported on the purification and characterization of a cellular inhibitor of PKR (referred to as p58), which is activated during influenza virus infection. Subsequent cloning and sequencing has revealed that p58 is a member of the tetratricopeptide repeat (TPR) family of proteins. To further examine the physiological role of this PKR inhibitor, we stably transfected NIH 3T3 cells with a eukaryotic expression plasmid containing p58 cDNA under control of the cytomegalovirus early promoter. By taking advantage of a recently characterized p58 species-specific monoclonal antibody, we isolated cell lines that overexpressed p58. These cells exhibited a transformed phenotype, growing at faster rates and higher saturation densities and exhibiting anchorage-independent growth. Most importantly, inoculation of nude mice with p58-overexpressing cells gave rise to the production of tumors. Finally, murine PKR activity and endogenous levels of eIF-2 alpha phosphorylation were reduced in the p58 expressing cell lines compared with control cells. These data, taken together, suggest that p58 functions as an oncogene and that one mechanism by which the protein induces malignant transformation is through the down-regulation of PKR and subsequent deregulation of protein synthesis.