Folding of pyrimidine-enriched RNA fragments from the vicinity of the internal ribosomal entry site of hepatitis A virus

Hepatitis A Virus Genome Organization and Replication Strategy

Hepatitis A virus (HAV) is a positive-strand RNA virus classified in the genus Hepatovirus of the family Picornaviridae It is an ancient virus with a long evolutionary history and multiple features of its capsid structure, genome organization, and replication cycle that distinguish it from other mammalian picornaviruses. HAV proteins are produced by cap-independent translation of a single, long open reading frame under direction of an inefficient, upstream internal ribosome entry site (IRES). Genome replication occurs slowly and is noncytopathic, with transcription likely primed by a uridylated protein primer as in other picornaviruses. Newly produced quasi-enveloped virions (eHAV) are released from cells in a nonlytic fashion in a unique process mediated by interactions of capsid proteins with components of the host cell endosomal sorting complexes required for transport (ESCRT) system.

RNA interaction and cleavage of poly(C)-binding protein 2 by hepatitis A virus protease

The poly(rC)-binding protein PCBP2 has multiple functions in post-transcriptional control of host and viral gene expression. Since it interacts with picornaviral RNA structures, it was proposed that PCBP2 regulates viral genome translation and replication. The hepatitis A virus (HAV), an atypical picornavirus, contains an unusual pyrimidine-rich tract (pY1) with unknown functions. Using in vivo and in vitro assays, we provide direct evidence that PCBP2 interacts with pY1 and that binding is mediated by KH domains 1 and 3. Proteolytic cleavage by the viral protease 3C generates a C-terminally truncated polypeptide with highly reduced RNA affinity. The results suggest that during HAV infection PCBP2 cleavage might specifically down-regulate viral protein synthesis, thereby giving way to viral RNA synthesis.