title: New insights into internal ribosome entry site elements relevant for viral gene expression.
abstract: A distinctive feature of positive-strand RNA viruses is the presence of high-order structural elements at the untranslated regions (UTR) of the genome that are essential for viral RNA replication. The RNA of all members of the family Picornaviridae initiate translation internally, via an internal ribosome entry site (IRES) element present in the 5' UTR. IRES elements consist of cis-acting RNA structures that usually require specific RNA-binding proteins for translational machinery recruitment. This specialized mechanism of translation initiation is shared with other viral RNAs, e.g. from hepatitis C virus and pestivirus, and represents an alternative to the cap-dependent mechanism. In cells infected with many picornaviruses, proteolysis or changes in phosphorylation of key host factors induces shut off of cellular protein synthesis. This event occurs simultaneously with the synthesis of viral gene products since IRES activity is resistant to the modifications of the host factors. Viral gene expression and RNA replication in positive-strand viruses is further stimulated by viral RNA circularization, involving direct RNA-RNA contacts between the 5' and 3' ends as well as RNA-binding protein bridges. In this review, we discuss novel insights into the mechanisms that control picornavirus gene expression and compare them to those operating in other positive-strand RNA viruses.
authors.affiliation: Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas - Universidad Autónoma de Madrid, Cantoblanco 28049 Madrid, Spain.
authors.forename: Encarnación
authors.initials: E
authors.lastname: Martínez-Salas
authors.affiliation: Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas - Universidad Autónoma de Madrid, Cantoblanco 28049 Madrid, Spain.
authors.forename: Almudena
authors.initials: A
authors.lastname: Pacheco
authors.affiliation: Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas - Universidad Autónoma de Madrid, Cantoblanco 28049 Madrid, Spain.
authors.forename: Paula
authors.initials: P
authors.lastname: Serrano
authors.affiliation: Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas - Universidad Autónoma de Madrid, Cantoblanco 28049 Madrid, Spain.
authors.forename: Noemi
authors.initials: N
authors.lastname: Fernandez
mesh_terms: D015967:Gene Expression Regulation, Viral; D016174:Hepacivirus / Q000235:genetics / Q000378:metabolism; D010849:Picornaviridae / Q000235:genetics / Q000378:metabolism; D014176:Protein Biosynthesis; D012328:RNA Viruses / Q000235:genetics / Q000378:metabolism*; D012367:RNA, Viral / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism*; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D012367:RNA, Viral; D014764:Viral Proteins