A mutual regulatory loop between transcription factor Yin Yang 1 and hepatitis B virus replication influences chronic hepatitis B

Hepatitis B virus (HBV) infections pose a major threat to human health. HBV can upregulate the expression of the transcription factor Yin Yang 1 (YY1) in in vitro cytological experiments, suggesting an association between YY1 and HBV infection. However, data on YY1 expression in chronic hepatitis B (CHB) patients are lacking. In this study, we aimed to assess the correlation between YY1 expression and HBV infection. We detected serum YY1 levels in 420 patients with chronic HBV infection, 30 patients with chronic hepatitis C virus infection, and 32 healthy controls using an enzyme-linked immunosorbent assay. The correlation between YY1 levels and clinical parameters was analyzed. Meanwhile, the changes of YY1 before and after interferon or entecavir treatment were analyzed. YY1 levels in the liver tissues were detected using immunofluorescence staining. The expression of YY1 in HBV-expressing cells was detected through western blotting. Meanwhile, we explored the effects of YY1 on HBV replication and gene expression. We found that YY1 was highly expressed in the serum and liver tissues of CHB patients. Serum YY1 levels positively correlated with HBV DNA and hepatitis B surface antigen (HBsAg). Additionally, HBV DNA levels increased but HBsAg levels decreased after HBV-expressing cells overexpress YY1. In conclusion, our study demonstrates that YY1 plays an important role in HBV replication and gene expression, providing a potential target for the treatment of CHB.

Yin-Yang 1 and HBx protein activate HBV transcription by mediating the spatial interaction of cccDNA minichromosome with cellular chromosome 19p13.11

HBV cccDNA stably exists in the nuclei of infected cells as an episomal munichromosome which is responsible for viral persistence and failure of current antiviral treatments. However, the regulatory mechanism of cccDNA transcription by viral and host cellular factors is not well understood. In this study, we investigated whether cccDNA could be recruited into a specific region of the nucleus via specific interaction with a cellular chromatin to regulate its transcription activity. To investigate this hypothesis, we used chromosome conformation capture (3C) technology to search for the potential interaction of cccDNA and cellular chromatin through rcccDNA transfection in hepatoma cells and found that cccDNA is specifically associated with human chromosome 19p13.11 region, which contains a highly active enhancer element. We also confirmed that cellular transcription factor Yin-Yang 1 (YY1) and viral protein HBx mediated the spatial regulation of HBV cccDNA transcription by 19p13.11 enhancer. Thus, These findings indicate that YY1 and HBx mediate the recruitment of HBV cccDNA minichromosomes to 19p13.11 region for transcription activation, and YY1 may present as a novel therapeutic target against HBV infection.