Hepatitis B Virus Oncoprotein HBx Is Not an ATPase

Abstract

HBx is the smallest gene product of the Hepatitis B virus (HBV) and an oncogenic stimulus in chronic infections leading to liver disease. HBx interacts and interferes with numerous cellular processes, but its modes of action remain poorly understood. It has been invoked that HBx employs nucleotide hydrolysis to regulate molecular pathways or protein–protein interactions. In the present study, we reinvestigate the (d)NTP hydrolysis of recombinant HBx to explore its potential as a biochemical probe for antiviral studies. For our investigations, we employed existing soluble constructs (i.e., GST-HBx, MBP-HBx) and engineered new fusion proteins (i.e., DsbC-HBx, NusA-HBx), which are shown to serve as better systems for in vitro research. We performed mutational scanning of the computationally predicted NTP-binding domain, which includes residues associated with clinical cases. Steady-state and end-point activity assays, in tandem with mass-spectrometric analyses, reveal that the observed hydrolysis of all alleged HBx substrates, ATP, dATP, and GTP, is contingent on the presence of the GroEL chaperone, which preferentially copurifies as a contaminant with GST-HBx and MBP-HBx. Collectively, our findings provide new technical standards for recombinant HBx studies and reveal that nucleotide hydrolysis is not an operant mechanism by which HBx contributes to viral HBV carcinogenesis.

The HBx protein from hepatitis B virus coordinates a redox-active Fe-S cluster

“…In the present study, we focus on a soluble construct of HBx fused to disulfide bond isomerase C (DsbC-HBx) ( 23 ) to delve into the potential of HBx to coordinate transition metal ions. We find that HBx copurifies with Fe assembled into an Fe-S cluster, establishing HBx as an unrecognized Fe-S protein.…”

HBV Infection-Related PDZK1 Plays an Oncogenic Role by Regulating the PI3K-Akt Pathway and Fatty Acid Metabolism and Enhances Immunosuppression

“…The genetic factors that affect the outcome of HBV infection include human leukocyte antigen (HLA), cytokines, chemokines, mannose-binding proteins, vitamin D receptors, and Toll-like receptors (TLRs) [4][5][6][7][8], such as HLA-DPA1 rs3077 and HLA-DPB1 single nucleotide polymorphisms (SNPs) [9] and TNF-alpha promoter SNP and/ or haplotypes [10]. However, it is difficult to verify other genes in different populations.…”