丙型肝炎病毒NS5B基因的克隆及在大肠杆菌的分泌表达

CLONING AND EXPRESSION OF SOLUBLE HCV NS5B GENE IN EUKARYOCYTES

由于全长丙型肝炎病毒NS5B的疏水性 ,其表达和纯化非常困难。为了分泌表达NS5B ,作者对NS5B进行截短 ,缺失其疏水部分从而在大肠杆菌细胞中分泌表达HCVNS5B基因 ,并测定其活性。用逆转录多聚酶链反应 (RT PCR)的方法 ,设计截去NS5B疏水部分 ,PCR引物以HCV全长质粒pBRTM/HCV 1为模板 ,克隆到pGEM Teasy载体中 ,双酶切后回收连接到pET 2 1b中表达。大肠杆菌培养上清过柱纯化 ,进行十二烷基磺酸钠 聚丙烯酰胺凝胶电泳 (SDS PAGE)和Western免疫印迹分析 ,并用液闪近端分析 (SPA)法分析NS5BRdRp活性。成功地构建了NS5B基因大肠杆菌表达载体 ,Western免疫印迹显示NS5B蛋白在大肠杆菌细胞中表达。表达产物在大肠杆菌培养上清中存在 ,分子量 6 8kD左右 ,而且 [3 H]总掺入率达 6 90 0cpm。NS5B蛋白在大肠杆菌上清中表达成功 ,经过活性测定 。

HCV NS5B, acting as a RNA dependent replication enzyme,has emerged as an attractive protein used as a target for screenig of drugs against HCV NS5B, and plays an important role in HCV replication. In the report the gene expression of NS5B in E.coli was investigated. PCR was performed to gain the gene of HCV NS5B from plasmid pBRTM/HCV 1 which contains whole sequence of HCV, and the truncated NS5B gene containing no hydrophobic domain was cloned into pGEM Teasy vector. The gene of the truncated NS5B was cut from pGEM Teasy vector and cloned into E.coli expression plasmid pET 21b, then pET 21b NS5B was transfected into E.coli cells. The protein E.coli lysates were purified and analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS PAGE) and Western blotting assay. The RdRp activity of NS5B was examined by scintillation proximity assay (SPA). The truncated NS5B gene was successfully cloned into pET 21b. The results of SDS PAGE and Western blotting assay showed: ①the molecular weight of the expressed product was about 68 000 D, ②The truncated NS5B protein was existed in media of E.coli cells, ③The activity of NS5BDCT21 His from HCV 1b amounted to 6 900 cpm (total incorporation of approximately). These findings suggest that soluble NS5B can be successfully expressed in E.coli and could secret into media.