Regulation of the p21(WAF1/CIP1) Gene by the Core Protein of Hepatitis C Virus

• Main Authors: HEE SIOW WEY, 許曉薇
• Other Authors: Ming-Fu Chang
• Format: Others
• Language: zh-TW
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/10114290573676846858

碩士 === 國立臺灣大學 === 生化學研究所 === 87 === Hepatitis C virus (HCV) belongs to the Flaviviridae family and is an enveloped, positive-sense single-stranded RNA virus with a genome size of about 10 kb. HCV is a major cause of chronic hepatitis worldwide, and is strongly associated with the development of hepatocellular carcinoma. Besides being a component of the viral nucleocapsid, there are abundant evidences to substantiate that the HCV core protein plays important roles in the regulation of cellular genes as well as the viral pathogenesis. p21(WAF1/CIP1) is the prototype of the protein family that inhibits cyclin-dependent kinases (CDK) and regulates cell cycle progression in eukaryotic cells. From recent studies, experimental evidences suggest that the HCV core protein can function as a repressor of p21 promoter. In this study, endogenous p21 was found to be decreased remarkably in both human hepatic and nonhepatic cell lines that stably expressed the HCV core protein. To define responsive elements mediated by the HCV core protein in the cultured cells, 5’-deletion analysis on the p21 promoter was performed with a luciferase reporter system. Nevertheless, difficulty was encountered due to the low basal luciferase activity of the deletion constructs. By performing gel mobility shift assay with various DNA fragments of the p21 promoter, a domain from —376 to -478 was demonstrated to complex specifically with cellular factors present in the HeLa nuclear extract. The level of the specific DNA-protein complexes were decreased when nuclear extract of an HCV core-expressing HeLa cell line (HeLa/C191) was used as the source of cellular factors. Further studies are needed to examine whether the defined domain of p21 promoter is regulated by the HCV core protein via a p53-independent pathway.