ABSTRACT
Chronic hepatitis B virus (HBV) infection is one of the leading causes of hepatocellular carcinoma (HCC). Ubiquitin-proteasome system (UPS) mediates the post-translational modification and degradation of protein in eukaryotic cells. Recent studies have revealed that UPS plays an important role in HBV infection and hepatocarcinogenesis. Targeting HBx to intervene in the progression of HBV infection or HBV-related HCC has become a research hotspot both domestically and internationally in recent years. This article reviewed the progress in HBx promoting HBV infection and hepatocarcinogenesis through UPS.
ABSTRACT
Objective:To study the role and mechanism of heat shock protein 70 (HSP70) in apolipoprotein B mRNA editing enzyme catalytic polypeptide-like 3B (APOBEC3B)-mediated inhibition of hepatitis B virus(HBV) replication.Methods:The interaction between HSP70 and APOBEC3B was analyzed by co-immunopreciptation (Co-IP) and GST pull-down. After treating Huh7 cells with siHSP70 or HSP70 inhibitor VER155008 or overexpressing HSP70 in Huh7 cells, changes in the antiviral effect of APOBEC3B were detected by Southern blot and real-time PCR; the deaminase activity of APOBEC3B was tested by differential DNA denaturation PCR(3D-PCR) and clone sequencing.Results:HSP70 could bind to APOBEC3B. Overexpression of HSP70 promoted the deaminase activity and anti-HBV activity of APOBEC3B. On the contrary, knockdown of HSP70 or using HSP70 inhibitor VER155008 would attenuate the deaminase activity and anti-HBV activity of APOBEC3B.Conclusions:HSP70 could promote the anti-HBV activity of APOBEC3B by enhancing the deaminase activity of APOBEC3B.
ABSTRACT
Objective To investigate the regulatory role of host restriction factor Moloney leukemia virus 10 (MOV10) protein in HBV replication. Methods Firstly, a HBV replication-expression plasmid was transfected into Huh7 cells to investigate the effect of HBV replication on MOV10 expression. Secondly, HBV DNA was extracted and measured by quantitative PCR ( qPCR) after knocking down the expression of endogenous MOV10 or enhancing the expression of exogenous MOV10. Furthermore, MOV10 conserved do-mainⅡenzyme active mutants (D645A, E646Q and G648A) were constructed and analyzed regarding their antiviral activities. The HBV replication plasmid and MOV10 expression plasmid were co-transfected into hu-man renal epithelial cells (HEK293) to investigate whether MOV10 could bind to HBV mRNA using RNA binding protein immunoprecipitation ( RIP) . Results The expression of MOV10 was increased after trans-fection of HBV replication plasmid into Huh7 cells. After knocking down the expression of endogenous MOV10 by siRNA in Huh7 cells, HBV replication was increased about 1. 5 times compared with control group, while the viral DNA level was significantly decreased in Huh7 cells that overexpressed MOV10. MOV10 domain Ⅱ mutants also significantly inhibited HBV replication. MOV10 could bind to 3. 5 kb HBV RNA. Conclusion In liver cancer cells, the expression of the host restriction factor MOV10 was associated with HBV replication. Its inhibitory effect against HBV replication was independent of its helicase activity, but might be associated with its binding activity with 3. 5kb HBV RNA.
ABSTRACT
Objective To investigate the mechanism of Roscovitine, an inhibitor of cyclin-dependent kinase (CDK), in inhibiting HBV replication.Methods Recombiant expression plasmids of SAMHD1 (sterile alpha motif and histidine/aspartic acid domain-containing protein 1) mutants that were defective in dNTPase (deoxynucleoside triphosphate triphosphohydrolase) activity and phosphorylation at the threonine (T) 592 residue were constructed.Huh7.0 cells were respectively co-transfected with different SAMHD1 mutants in combiantion with HBV replication plasmid to analyze whether the retroviral restriction ability of SAMHD1 was regulated by phosphorylation.The cytotoxicity of Roscovitine to Huh7 cells was evaluated by MTT assay.HBV core-associated DNA levels and phosphorylation of SAMHD1 in transfected Huh7.0 cells which were treated with different concentrations of Roscovitine were measured by Southern blot and Western blot assays.Results The SAMHD1 mutant that was defective in the dNTPase active site of D207N lost its ability to restrict HBV replication.Dephosphorylation of SAMHD1 at T592 enhanced its restriction on HBV.The median toxic concentration (TC50) of Roscovitine was 11.20 μmol/L.Both the HBV core-associated DNA levels and the phosphorylation of SAMHD1 were down-regulated by Roscovitine.Conclusion The anti-HBV function of SAMHD1 in dividing cells is regulated by phosphorylation.Roscovitine can inhibit the replication of HBV through reducing the phosphorylation of SAMHD1.