Department of Microbiology & Immunology, School of Biomedical Sciences, University of Otago, Dunedin 9054, New Zealand.
Viruses. 2019 Mar 4;11(3):217. doi: 10.3390/v11030217.
Murine norovirus (MNV) viral protein genome-linked (VPg) manipulates the cell cycle to induce a G0/G1 arrest and gain a beneficial replication environment. All viruses of the norovirus genus encode a VPg protein; however, it is unknown if the G0/G1 arrest induced by MNV VPg is conserved in other members of the genus. RNA transcripts encoding a representative viral VPg from five norovirus genogroups were transfected into RAW-Blue murine macrophages, and the percentage of cells in each phase of the cell cycle was determined. A G0/G1 cell cycle arrest was observed for all norovirus VPg proteins tested, and in the wider family the arrest was also conserved in rabbit hemorrhagic disease virus (RHDV) VPg and human sapovirus (HuSV) VPg. Truncation of MNV VPg shows that the first 62 amino acids are sufficient for a cell cycle arrest, and alignment of VPg sequences revealed a conserved motif in the N-terminal region of VPg. Analysis of VPg constructs with single N-terminal region point mutations, or exchange of N-terminal regions between VPg proteins, confirmed the importance of the N-terminal region for cell cycle arrest. These results provide evidence that G0/G1 cell cycle arrest is a conserved function of norovirus VPg proteins that involves the N-terminal region of these proteins.
鼠诺如病毒（MNV）病毒蛋白基因组连接（VPg）操纵细胞周期以诱导 G0/G1 期停滞并获得有利的复制环境。诺如病毒属的所有病毒都编码 VPg 蛋白；然而，尚不清楚 MNV VPg 诱导的 G0/G1 期停滞是否在属的其他成员中保守。转染编码来自五个诺如病毒基因组组的代表性病毒 VPg 的 RNA 转录本进入 RAW-Blue 鼠巨噬细胞，并确定细胞周期各阶段的细胞百分比。所有测试的诺如病毒 VPg 蛋白均观察到 G0/G1 细胞周期停滞，在更广泛的 家族中，兔出血症病毒 (RHDV) VPg 和人杯状病毒 (HuSV) VPg 也保守存在这种停滞。MNV VPg 的截断表明前 62 个氨基酸足以引起细胞周期停滞，并且 VPg 序列的比对显示 VPg 的 N 端区域存在保守基序。对具有单个 N 端区域点突变的 VPg 构建体或 VPg 蛋白之间 N 端区域的交换进行分析，证实了 N 端区域对细胞周期停滞的重要性。这些结果提供了证据表明 G0/G1 细胞周期停滞是诺如病毒 VPg 蛋白的保守功能，涉及这些蛋白的 N 端区域。
