Abstract
Viral protein synthesis is completely dependent upon the translational machinery of the host cell. However, many RNA virus transcripts have marked structural differences from cellular mRNAs that preclude canonical translation initiation, such as the absence of a 5′ cap structure or the presence of highly structured 5′UTRs containing replication and/or packaging signals. Furthermore, whilst the great majority of cellular mRNAs are apparently monocistronic, RNA viruses must often express multiple proteins from their mRNAs. In addition, RNA viruses have very compact genomes and are under intense selective pressure to optimize usage of the available sequence space. Together, these features have driven the evolution of a plethora of non-canonical translational mechanisms in RNA viruses that help them to meet these challenges. Here, we review the mechanisms utilized by RNA viruses of eukaryotes, focusing on internal ribosome entry, leaky scanning, non-AUG initiation, ribosome shunting, reinitiation, ribosomal frameshifting and stop-codon readthrough. The review will highlight recently discovered examples of unusual translational strategies, besides revisiting some classical cases.
Highlights
In picornaviruses, where internal ribosome entry sites (IRESes) were first described (Jang et al, 1988; Pelletier & Sonenberg, 1988), two major classes have been identified that are distinct in structure and sequence, but typically require most of the canonical initiation factors for activity, including eIF3, eIF4A and the C-terminal domain of eIF4G, besides the eIF2–Met–tRNAi–GTP ternary complex
This review has focused on the unusual translational mechanisms that viruses employ to cope with the unique constraints imposed by their compact genomes and atypical mRNAs, a number of RNA viruses have evolved various non-translational mechanisms that in some ways achieve similar results
It is clear that RNA viruses provide a fascinating plethora of examples of non-standard mechanisms for gene expression
Summary
In picornaviruses, where IRESes were first described (Jang et al, 1988; Pelletier & Sonenberg, 1988), two major classes (types I and II) have been identified that are distinct in structure and sequence, but typically require most of the canonical initiation factors for activity, including eIF3, eIF4A and the C-terminal domain of eIF4G, besides the eIF2–Met–tRNAi–GTP ternary complex (reviewed by Belsham, 2009; other types of picornavirus IRES – such as those found in Aichi virus and hepatitis A virus – will not be discussed here) In those picornaviruses harbouring type I IRESes (poliovirus and other enteroviruses), the initiator AUG for translation of the viral polyprotein is http://vir.sgmjournals.org located some distance downstream of the site of recruitment of the 40S subunit to the IRES, and some form of scanning is required to locate it. Umbravirus Luteovirus Polerovirus Polerovirus Sobemovirus Tombusvirus Aureusvirus Pelarspovirus Panicovirus Machlomovirus Machlomovirus Tymovirus Potexvirus Hordeivirus RNA2 Pecluvirus RNA2 Arterivirus Betacoronavirus (some species) Hepevirus Caliciviridae – murine norovirus, neboviruses, some sapoviruses Omegatetravirus RNA2 Mammalian orthoreovirus, segment S1 Avian orthoreovirus and Nelson Bay orthoreovirus, segment S1 Rotavirus A, segment 11 Respirovirus Morbillivirus Henipavirus Orthobunyavirus (some species) Hantavirus (some species) Orthomyxoviridae – influenza virus B Orthomyxoviridae – influenza virus A Isavirus, segment 8 Tungrovirus Badnavirus
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
