Hepatitis B doubly spliced protein (HBDSP) promotes hepatocellular carcinoma cell apoptosis via ETS1/GATA2/YY1-mediated p53 transcription

Abstract

ABSTRACT Chronic hepatitis B virus (HBV) infection represents an important global public health concern. The spliced variants generated by RNA splicing from 3.5-kb HBV pre-genomic RNA are involved in chronic hepatitis B pathogenicity and associated with hepatocellular carcinoma development. Although the HBV spliced variants with a length of 2.2 kb have been widely detected, their roles in the development of HBV-associated liver diseases remain unknown. In the present study, the pro-apoptotic effects of hepatitis B doubly spliced protein (HBDSP) encoded by 2.2-kb doubly spliced variants of HBV in wild-type p53 (wt -p53 ) hepatocytes were determined. We primarily found that HBDSP promoted the apoptosis of HepG2 and SMMC-7721 cells with wt -p53 . The role of wt- p53 in HBDSP-induced apoptosis was further investigated. It was demonstrated that HBDSP upregulated p53 and phospho-p53 (Ser15) expression and herein stimulated the p53 -dependent apoptotic signaling pathway. Mechanistically, HBDSP indirectly transactivated the p53 promoter in an ETS1-, GATA2-, and YY1-dependent manner, in which HBDSP increased the nuclear translocation of ETS1, GATA2, and YY1. Besides, it was demonstrated that HBDSP could promote cellular apoptosis and activate p53 -dependent apoptotic signaling pathway, resulting in increased secretion of HBV DNA, HBsAg, and HBeAg in HepG2.2.15 cells and HBV-infected HepG2-NTCP cells. Taken together, our results reveal a novel mechanism by which HBDSP promotes ETS1/GATA2/YY1-dependent p53 gene transcription and induces apoptosis in wt- p53 cells, and increases the production of HBV progeny and viral antigens. These findings may provide novel insight into the pathogenesis of HBDSP involved in HBV-associated liver diseases. IMPORTANCE Hepatitis B virus (HBV) spliced variants are associated with viral persistence or pathogenicity. Hepatitis B doubly spliced protein (HBDSP), which has been previously reported as a pleiotropic transactivator protein, can potentially serve as an HBV virulence factor. However, the underlying mechanisms of HBDSP in HBV-associated liver diseases remain to be elucidated. In this study, we revealed that HBDSP promotes cellular apoptosis and induces wt- p53 -dependent apoptotic signaling pathway in wt- p53 hepatocellular cells by transactivating p53 transcription, and increases the release of HBV progeny. Therefore, HBDSP may promote the HBV particles release through wt- p53 -dependent hepatocellular apoptosis. Our findings suggest that blocking HBDSP-induced wt- p53 -dependent apoptosis might have therapeutic values for chronic hepatitis B.