DNMT3a Regulates the Proliferation and Apoptosis of Hepatocellular Carcinoma Cells Through RYBP Methylation

Recent studies have demonstrated that RING1 and YY1 Binding Protein (RYBP) participates in cell cycle arrest and apoptosis regulation, yet the mechanism by which RYBP is regulated in hepatocellular carcinoma (HCC) remains poorly defined. In this study, we detected the expression levels of RYBP and DNMT3a in human HCC cell lines and the immortalized normal liver cell line THLE‐3 using quantitative real‐time PCR (qPCR) and Western blot. Methylation‐specific PCR (MSP), dual‐luciferase reporter assays and ChIP‐qPCR were performed to investigate the interaction between DNMT3a and the RYBP promoter. EdU incorporation, CCK‐8 and flow cytometry assays were adopted to assess cell proliferation and apoptosis. We found that RYBP was markedly downregulated in HCC cell lines. Ectopic overexpression of RYBP inhibited proliferation, triggered G1‐phase cell cycle arrest and facilitated apoptosis in HCC cells. DNMT3a was overexpressed in HCC cell lines and repressed RYBP expression through promoter methylation. Knockdown of DNMT3a reduced methylation of the RYBP promoter, restored RYBP expression, suppressed cell proliferation and induced apoptosis in HCC cells. Furthermore, RYBP silencing reversed the biological phenotypes induced by DNMT3a knockdown. Collectively, our findings reveal that DNMT3a modulates cell proliferation and apoptosis in HCC via epigenetic repression of RYBP by mediating RYBP promoter methylation.