Mechanism of Roscovitine in inhibiting HBV replication

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. Key words: Roscovitine; Hepatitis B virus; SAMHD1; Phosphorylation; Inhibition