Regulation of hepatitis B virus gene expression and replication

Hepatitis B virus (HBV) is an important etiological factor for liver diseases. The study presented in this dissertation focuses on the regulation of HBV life cycle by various host factors.; HNF4 and HNF1 are two important liver-specific transcription factors. A natural occurring double mutant in HBV core promoter (1765 A to T and 1767 G to A) creates a binding site for the transcription factor HNF1 and a mutant form of X protein. It also selectively abolishes the binding of several nuclear receptors without affecting that of HNF4. My study showed that HNF4 could stimulate the expression of the precore RNA and the core RNA from the core promoter of both the wild-type (WT) HBV and the double mutant. In contrast, HNF1 suppressed the precore RNA expression of the double mutant but not the wild type. X protein did not affect the HNF4 activity on the core promoter and affected the HNF1 activity on the core promoter of only the double mutant.; Two host kinases, SRPKI and SRPK2, could suppress HBV replication by reducing the packaging efficiency of the pgRNA without affecting the formation of the core particles. This inhibition is independent of the kinase activity of SRPKs or the phosphorylation of the core protein.; The effect of Ras signaling pathway on the replication of HBV was also studied in this dissertation. The Ras-ERK pathway could suppress the replication of HBV in both Huh7 and HepG2 cells. This suppression was independent of the X protein and most likely occurred at the transcription level. Further study with deletion-mapping analysis showed the existence of multiple Ras-responsive elements in HBV core promoter and its upstream ENI and ENII enhancers.; The studies presented in this dissertation thus indicated complicated regulation of Hepatitis B Virus life cycle by the host cellular factors. These studies have led to a better understanding of the cross talk between the virus and the host. Further work in this area will shed light on the design of new drugs, which will eventually lead to the cure of hepatitis B.