Cellular protein modification by poliovirus: The two faces of Poly(rC)-binding protein
Cellular protein modification by poliovirus: The two faces of Poly(rC)-binding protein
复制标题
DOI：
10.1128/jvi.01013-07
复制
发表时间：
2007-09-01
影响因子：
5.4
通讯作者：
Semler, Bert L.
中科院分区：
文献类型：
--
作者：
Perera, Rushika;Daijogo, Sarah;Semler, Bert L.
在小核糖核酸病毒感染期间，几种细胞蛋白质被病毒编码的蛋白酶切割。这种裂解事件可能涉及细胞内病毒生命周期期间的动态变化，从病毒翻译到宿主关闭到RNA复制到病毒体组装。例如，已经提出存在由RNA结合蛋白亲和力的变化介导的从脊髓灰质炎病毒翻译到RNA复制的主动转换。这种开关可能是控制翻译和负链病毒RNA合成的模板选择的机制，这两个过程使用相同的正链RNA作为模板，但以相反的方向进行。细胞蛋白聚（rC）结合蛋白（PCBP）被确定为调节这种机制的主要候选人。在哺乳动物细胞中PCBP的四种不同亚型中，PCBP 2是具有I型内部核糖体进入位点元件的小核糖核酸病毒基因组上的翻译起始以及RNA复制所需的。通过其三个K-同源（KH）结构域，PCPB 2与病毒翻译和复制机制的组分形成功能性蛋白质-蛋白质和RNA-蛋白质复合物。我们发现亚型PCBP 1和-2在脊髓灰质炎病毒感染的中后期被切割。在体外切割试验的基础上，我们确定，这种切割事件是由病毒蛋白酶3C/3CD介导的。初级切割发生在KH 2和KH 3结构域之间的接头中，导致缺少KH 3结构域的截短的PCBP 2。这种被切割的蛋白质，称为PCBP 2-Delta KH 3，不能在翻译中发挥作用，但在病毒RNA复制中保持其活性。我们提出，通过KH 3结构域的丢失，并因此失去其在翻译中发挥作用的能力，PCBP 2可以介导从病毒翻译到RNA复制的转换。
During picornavirus infection, several cellular proteins are cleaved by virus-encoded proteinases. Such cleavage events are likely to be involved in the changing dynamics during the intracellular viral life cycle, from viral translation to host shutoff to RNA replication to virion assembly. For example, it has been proposed that there is an active switch from poliovirus translation to RNA replication mediated by changes in RNA-binding protein affinities. This switch could be a mechanism for controlling template selection for translation and negative-strand viral RNA synthesis, two processes that use the same positive-strand RNA as a template but proceed in opposing directions. The cellular protein poly (rC)-binding protein (PCBP) was identified as a primary candidate for regulating such a mechanism. Among the four different isoforms of PCBP in mammalian cells, PCBP2 is required for translation initiation on picornavirus genomes with type I internal ribosome entry site elements and also for RNA replication. Through its three K-homologous (KH) domains, PCPB2 forms functional protein-protein and RNA-protein complexes with components of the viral translation and replication machinery. We have found that the isoforms PCBP1 and -2 are cleaved during the mid-to-late phase of poliovirus infection. On the basis of in vitro cleavage assays, we determined that this cleavage event was mediated by the viral proteinases 3C/3CD. The primary cleavage occurs in the linker between the KH2 and KH3 domains, resulting in truncated PCBP2 lacking the KH3 domain. This cleaved protein, termed PCBP2-Delta KH3, is unable to function in translation but maintains its activity in viral RNA replication. We propose that through the loss of the KH3 domain, and therefore loss of its ability to function in translation, PCBP2 can mediate the switch from viral translation to RNA replication.