Suzuki R, Matsuura Y, Suzuki T, Ando A, Chiba J, Harada S, Saito I, Miyamura T
Department of Virology II, National Institute of Health, Tokyo, Japan.
J Gen Virol. 1995 Jan;76 ( Pt 1):53-61. doi: 10.1099/0022-1317-76-1-53.
The core protein of hepatitis C virus (HCV) is considered to be cleaved from the N terminus of the large precursor polyprotein by cellular signalase. The HCV cDNA encoding the core protein was expressed (i) in monkey COS cells by a plasmid expression vector driven by the SR alpha promoter, and (ii) in insect cells by a recombinant baculovirus. The expressed product had an M(r) of 22,000 and was located in the cytoplasm. When the C-terminal hydrophobic domains were deleted, however, the truncated core proteins were translocated into the nucleus. The truncated core proteins were located in the nucleus even when they were expressed as a fusion protein with E. coli beta-galactosidase, which is essentially localized in the cytoplasm. Plasmids containing HCV cDNAs with a deletion in one of the regions encoding clusters of basic amino acids were expressed in COS cells and the localization of the core protein was examined. The residues PRRGPR were suggested to play an important role in nuclear localization. HCV is an RNA virus and its life cycle was originally considered to be confined to the cytoplasm; the present study, however, suggests that the HCV core protein can translocate into the nucleus under certain circumstances.
丙型肝炎病毒（HCV）的核心蛋白被认为是由细胞信号酶从前体多聚蛋白的N端切割而来。编码核心蛋白的HCV cDNA（i）通过由SRα启动子驱动的质粒表达载体在猴COS细胞中表达，（ii）通过重组杆状病毒在昆虫细胞中表达。表达产物的相对分子质量为22000，定位于细胞质中。然而，当C端疏水结构域被缺失时，截短的核心蛋白会转运至细胞核中。即使截短的核心蛋白与主要定位于细胞质中的大肠杆菌β-半乳糖苷酶作为融合蛋白表达时，它们仍定位于细胞核中。含有在编码碱性氨基酸簇的区域之一中存在缺失的HCV cDNA的质粒在COS细胞中表达，并检测核心蛋白的定位。推测PRRGPR残基在核定位中起重要作用。HCV是一种RNA病毒，其生命周期最初被认为局限于细胞质中；然而，本研究表明，在某些情况下，HCV核心蛋白可以转运至细胞核中。
