Hepatitis B virus X protein (HBx), encoded by hepatitis B virus (HBV) genome, plays a crucial role in the pathogenesis of liver cancer, and we previously showed that reactive oxygen species (ROS) significantly elevated the HBx protein levels. First, I herein investigated the role of antioxidants in regulation of HBx protein expression and their clinical relevance. Overexpression of catalase or superoxide dismutase 2 (MnSOD) induced a significant decrease in HBx expression level. Complete disruption for cysteine residues in HBx protein resulted in a dramatically reduced HBx protein level and this HBx Cys-null (Cys-) mutant no longer responded to catalase, suggesting that disulfide bonds in HBx are important for its protein stability. Moreover, Huh7-Cys- cells failed to generate colonies in clonogenic survival assays, while Huh7 cells expressing wild-type HBx (Huh7-X) yielded a significant number of colonies. Next, I analyzed 50 human HBV-induced hepatocellular carcinoma (HCC) samples. Seventy-eight percent of HCC samples contained lower catalase levels than surrounding tissues. Importantly, patients with a high T/N (tumor/non-tumor tissue) ratio for catalase showed significantly longer survival than those with a low T/N ratio. Interestingly, there was a significant inverse relationship between catalase and HBx expression levels in stage IV HCCs. Thus, catalase expression in HCC patients can be clinically useful for prediction of patient survival and restoration. Second, HBx in the host cells was found to be tightly associated with protein called HBxAP (HBx-associated protein), which was identified as a subunit of chromatin remodeler RSF complex. I found that RSF1 protein was overexpressed in HBV-related HCC specimens along with elevated HBx protein compared to those in surrounding liver tissues. Notably, depletion of RSF1 induced the premature separation of sister chromatids and fluorescence resonance energy transfer (FRET) analysis revealed that centromeric H3K9me3 levels were reduced in mitotic RSF1 depleted cells. Moreover, in histone peptide array RSF1 widely bound to modified histone H3 peptides except that it no longer interacted with the phosphorylated histone H3 peptide at the Ser28. Further investigation is needed to reveal underlying mechanisms by which RSF1 regulates chromosomal instability. Taken together, these findings suggest that HBx and RSF1 contribute to liver cancer development.