Competing and noncompeting activities of miR-122 and the 5′ exonuclease Xrn1 in regulation of hepatitis C virus replication
Competing and noncompeting activities of miR-122 and the 5′ exonuclease Xrn1 in regulation of hepatitis C virus replication
复制标题
DOI：
10.1073/pnas.1213515110
复制
发表时间：
2013-01-29
影响因子：
11.1
通讯作者：
Lemon, Stanley M.
中科院分区：
文献类型：
--
作者：
Li, You;Masaki, Takahiro;Lemon, Stanley M.
丙型肝炎病毒（HCV）复制依赖于microRNA 122（miR-122），这是一种肝脏特异性microRNA，可将Argonaute 2募集到病毒基因组的5'端，使其稳定并减缓其在无细胞反应和感染细胞中的衰变。在这里，我们描述了miR-122提供保护的RNA降解途径。转染的HCV RNA被5'外切核酸酶Xrn 1和3'外切核酸酶外切体复合物降解，而感染细胞内复制的RNA主要被Xrn 1降解，外切体没有贡献。与此一致，对感染细胞中RNA降解中间体的5'和3'末端的测序证实了5'衰变是HCV RNA降解的主要途径。Xrn 1敲低增强HCV复制，表明Xrn 1衰变和病毒复制酶竞争在感染细胞内设置RNA丰度。Xrn 1敲除和miR-122补充对病毒RNA衰变速率具有相等的、冗余的和非累加的影响，表明miR-122保护HCV RNA免于5'衰变。然而，Xrn 1敲低并不能挽救miR-122结合缺陷的病毒突变体的复制，这表明miR-122在病毒生命周期中具有额外的尚未表征的功能。
Hepatitis C virus (HCV) replication is dependent on microRNA 122 (miR-122), a liver-specific microRNA that recruits Argonaute 2 to the 5' end of the viral genome, stabilizing it and slowing its decay both in cell-free reactions and in infected cells. Here we describe the RNA degradation pathways against which miR-122 provides protection. Transfected HCV RNA-is degraded by both the 5' exonuclease Xrn1 and 3' exonuclease exosome complex, whereas replicating RNA within infected cells is degraded primarily by Xrn1 with no contribution from the exosome. Consistent with this, sequencing of the 5' and 3' ends of RNA degradation intermediates in infected cells confirmed that 5' decay is the primary pathway for HCV RNA degradation. Xrn1 knockdown enhances HCV replication, indicating that Xrn1 decay and the viral replicase compete to set RNA abundance within infected cells. Xrn1 knockdown and miR-122 supplementation have equal, redundant, and nonadditive effects on the rate of viral RNA decay, indicating that miR-122 protects HCV RNA from 5' decay. Nevertheless, Xrn1 knockdown does not rescue replication of a viral mutant defective in miR-122 binding, indicating that miR-122 has additional yet uncharacterized function(s) in the viral life cycle.