THE MECHANISMS OF ANTI-APOPTOTIC EFFECTS BY HEPATITIS C VIRUS CORE PROTEIN

为了阐明丙型肝炎和肝细胞癌的分子机制，本研究分析了丙型肝炎病毒核心蛋白抗细胞凋亡的机制。取得的成果如下：1.分析了核心蛋白激活细胞转录因子NF-κB的分子机制，认为这是核心蛋白抗细胞凋亡作用的重要机制之一。结果表明：(1)丙型肝炎病毒核心蛋白定位于细胞质，尤其是内质网膜上，对核转录因子κB的激活具有重要意义。(2)我们发现，与真正的核心蛋白一样，核因子-κB激活所需的最小区域位于核心蛋白的氨基末端，从aa20到aa80。(3)我们试图以核心蛋白的aa20到aa80区域为诱饵，对酵母双杂交系统获得的几个cDNA克隆进行鉴定。(4)我们发现，核心蛋白增强了通过过表达IKKβ而诱导的NF-κB的活性。ikkβ是一种磷酸化I DNA的激酶，但不增强ikk DNA的活性。提示：1.核心蛋白作用于NF-βB激活途径中IKKκ下游的点，从而增强了NF-κB的活性。我们分析了核心蛋白激活MAP激酶途径的分子机制，结果表明，核心蛋白通过未知的机制增强转录因子ELK1的活性，这与已知的激活反应不同。由于核心蛋白激活转录因子似乎与抑制细胞凋亡、丙型肝炎病毒持续感染和肝细胞癌密切相关，因此，分子机制的进一步分析正在进行中。

To clarifiy the molecular mechanism of hepatitis and hepatocellular carcinoma caused by hepatitis C virus (HCV), we analysed the mechanism of anti-apoptotic effect by HCV core protein in this research project. The achievements are listed bellow.1. Results obtained from analysis of the molecular mechanism for activation of cellular transcription factor NF-κB by HCV core protein which is thought be one of important machinary for the anti-apoptotic effect of the core portein. are shown as follows ;(1) From th edeletion analysis and and the observation of subcellular localization, it was revealed that the localization of the HCV core protein in the cytoplasm, especially on the endoplasmic reticulum membranes, is important for the NF-κB activation. .(2) We found that the minimum region required for NF-κB activation just like as authentic core protein is located at the amino-terminal portion, from aa20 to aa80, of the HCV core protein.(3) We are trying to characterize several cDNA clones obtained by yeast two hybrid system using the region from aa 20 to aa 80 of the core as a bait.(4) We showed that the core protein enhanced the NF-κB activity induced by the overexpression of IKKβ, which is a kinase for the phosphorylation of IκB, without augmentation of IKKβ activity, suggesting that the core protein affects the point downstream of IKKβin thee NF-κB activation pathway to enhance the NF-κB activity.2. We analysed the molecular mechanism of activation of MAP kinase pathway by the core protein and obtained the results showing that the coree protein augments the activity of transcription factor Elk1 by the unknow mechaism which is different from the well-known kination reaction.Since the activation of the tramscription factors by the HCV core protein seems to be closely related with the suppression of apoptosis, persistent infection of HCV, and hepatocellular carcinogenesis, further analysis of molecular mechanisms is now underway.