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[摘要]：BACKGROUND & AIMS: The nonstructural SA (NS5A) protein of hepatitis C virus (HCV) plays a critical role in HCV replication and is an attractive target for the therapy of HCV infection. So far, little is known about the posttranslational regulation of NS5A protein and its precise role in HCV RNA replication. Our objectives were to elucidate the down-regulation of NS5A protein and HCV RNA replication by zinc mesoporphyrin (ZnMP) and the mechanism by which this process occurs. METHODS: Human hepatoma cells expressing HCV proteins were used to investigate the posttranslational regulation of ZnMP on NS5A protein by Western blots and immunoprecipitation. Real-time quantitative reverse transcription polymerase chain reaction was used to determine the effects of ZnMP on HCV RNA replication. RESULTS: ZnMP selectively and markedly down-regulated NSSA protein levels by increasing degradation of NS5A protein (half-life fell from 18.7 hours to 2.7 hours). The proteasome inhibitors epoxomicin and MG132 significantly abrogated degradation of NS5A protein by ZnMP without affecting levels of NS5A in the absence of ZnMP. Analysis of immunoprecipitates with an antiubiquitin antibody revealed polyubiquitination of NSSA, suggesting that ZnMP induces ubiquitination of NS5A protein. In addition, 10 mu mol/L of ZnMP reduced HCV replication by similar to 63% in the Con1 replicon cells, similar to 70% in J6/Japanese Eulminant hepatitis 1 HCV-transfected cells, and similar to 90% in J6/Japanese fulminant hepatitis 1 HCV-infected cells without affecting cell viability. CONCLUSIONS: ZnMP produces a rapid and profound downregulation of the NS5A protein by enhancing its polyubiquitination and proteasome-dependent catabolism. ZnMP may hold promise as a novel agent to treat HCV infection. |
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