The m6A methylation system limits hepatitis B virus replication

N6-methyladenosine (m6A) is a common RNA modification, which plays a critical role in RNA fate and regulating such aspects as splicing, stability, nuclear export, and translation efficiency. The introduction, removal, and recognition of m6A modifications in RNA are regulated by a number of factors, known as writer, eraser, and reader proteins. It is known that the m6A modification can play an important role in the life cycle of viruses, including hepatitis B virus. The m6A methylation system has a significant impact on the hepatitis B viral cycle (HBV), particularly, on stability of mRNA transcripts, encapsidation efficiency, and reverse transcription of HBV pgRNA. In this study, we assessed the effect of knockout and activation of expression of several factors of the m6A methylation system on the HBV viral cycle, including pregenomic RNA (pgRNA) and circular covalently closed DNA (cccDNA). The study was carried out using the StCas9 nuclease system for knockout and the dCas9-p300 system for activation of gene expression. The levels of pgRNA and cccDNA were estimated by real-time PCR. The data obtained show the restriction of the viral cycle at the basal level by the factors METTL3, METTL14, METTL16, FTO, JMJD6, and hnRNPA2B1, as well as suppression of the viral cycle with overexpression of all of the above factors, except for hnRNPA2B1.