N6-methyladenosine modification of the 5' epsilon structure of the HBV pregenome RNA regulates its encapsidation by the viral core protein.

ABSTRACT: Hepatitis B virus (HBV) contains a partially double-stranded DNA genome. During infection, its replication is mediated by reverse transcription (RT) of an RNA intermediate termed pregenomic RNA (pgRNA) within core particles in the cytoplasm. An epsilon structural element located in the 5' end of the pgRNA primes the RT activity. We have previously identified the N6-methyladenosine (m⁶A)-modified DRACH motif at 1905 to 1909 nucleotides in the epsilon structure that affects myriad functions of the viral life cycle. In this study, we investigated the functional role of m⁶A modification of the 5' ε (epsilon) structural element of the HBV pgRNA in the nucleocapsid assembly. Using the m⁶A site mutant in the HBV 5' epsilon, we present evidence that m⁶A methylation of 5' epsilon is necessary for its encapsidation. The m⁶A modification of 5' epsilon increased the efficiency of viral RNA packaging, whereas the m⁶A of 3' epsilon is dispensable for encapsidation. Similarly, depletion of methyltransferases (METTL3/14) decreased pgRNA and viral DNA levels within the core particles. Furthermore, the m⁶A modification at 5' epsilon of HBV pgRNA promoted the interaction with core proteins, whereas the 5' epsilon m⁶A site-mutated pgRNA failed to interact. HBV polymerase interaction with 5' epsilon was independent of m⁶A modification of 5' epsilon. This study highlights yet another pivotal role of m⁶A modification in dictating the key events of the HBV life cycle and provides avenues for investigating RNA-protein interactions in various biological processes, including viral RNA genome encapsidation in the context of m⁶A modification.

SUBMITTER: Kim GW 

PROVIDER: S-EPMC8851549 | biostudies-literature | 2022 Feb

REPOSITORIES: biostudies-literature