Suppression of hepatitis B viral gene expression by phosphoinositide 5-phosphatase SKIP

• Published in: Cellular microbiology Vol. 11; no. 1; pp. 37 - 50
• Main Authors: Hung, Chia-Sui, Lin, Yu-Li, Wu, Chun-I, Huang, Chiu-Jung, Ting, Ling-Pai
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 2009; Blackwell Publishing Ltd; Hindawi Limited
• Subjects: Cell Line; Cell Nucleus - chemistry; DNA Mutational Analysis; Gene Expression Regulation, Viral; Gene Knockdown Techniques; Gene Silencing; Hepatitis B; Hepatitis B Core Antigens - metabolism; Hepatitis B virus; Hepatitis B virus - physiology; Humans; Phosphoric Monoester Hydrolases - metabolism; Protein Binding; Protein Interaction Domains and Motifs; Protein Interaction Mapping; Virus Replication
• ISSN: 1462-5814; 1462-5822
• DOI: 10.1111/j.1462-5822.2008.01235.x

Human hepatitis B virus (HBV) causes acute and chronic hepatitis, cirrhosis and hepatocellular carcinoma. Here we report that HBV core protein interacts with a cellular SKIP (skeletal muscle and kidney enriched inositol phosphatase) protein, an endoplasmic reticulum-located phosphoinositide 5-phosphatase, both in vivo and in vitro. The minimal sequence required for interaction is the amino acid region from 116 to 149 for the core protein and the SKIP carboxyl homology (SKICH) domain for SKIP. When HBV replicates in HuH-7 cells, overexpressed SKIP localizes to nucleus in addition to ER and suppresses HBV gene expression and replication. SKIP loses its nuclear localization and suppressive effect during replication of a core-negative HBV mutant. HBV gene expression is enhanced significantly when endogenous SKIP expression is knocked down by a SKIP-specific siRNA. SKIP mutation analysis shows that its 5-phosphatase activity is not required for the suppressive effect and that the suppression domain maps to amino acids 199-226. These results demonstrate that SKIP is translocated from endoplasmic reticulum into nucleus through its interaction with core protein and suppresses HBV gene expression via a novel suppression domain.