Publication Date:
2013-11-05
Description:
Hepatitis C virus (HCV) and classical swine fever virus (CSFV) messenger RNAs contain related (HCV-like) internal ribosome entry sites (IRESs) that promote 5'-end independent initiation of translation, requiring only a subset of the eukaryotic initiation factors (eIFs) needed for canonical initiation on cellular mRNAs. Initiation on HCV-like IRESs relies on their specific interaction with the 40S subunit, which places the initiation codon into the P site, where it directly base-pairs with eIF2-bound initiator methionyl transfer RNA to form a 48S initiation complex. However, all HCV-like IRESs also specifically interact with eIF3 (refs 2, 5-7, 9-12), but the role of this interaction in IRES-mediated initiation has remained unknown. During canonical initiation, eIF3 binds to the 40S subunit as a component of the 43S pre-initiation complex, and comparison of the ribosomal positions of eIF3 and the HCV IRES revealed that they overlap, so that their rearrangement would be required for formation of ribosomal complexes containing both components. Here we present a cryo-electron microscopy reconstruction of a 40S ribosomal complex containing eIF3 and the CSFV IRES. Remarkably, although the position and interactions of the CSFV IRES with the 40S subunit in this complex are similar to those of the HCV IRES in the 40S-IRES binary complex, eIF3 is completely displaced from its ribosomal position in the 43S complex, and instead interacts through its ribosome-binding surface exclusively with the apical region of domain III of the IRES. Our results suggest a role for the specific interaction of HCV-like IRESs with eIF3 in preventing ribosomal association of eIF3, which could serve two purposes: relieving the competition between the IRES and eIF3 for a common binding site on the 40S subunit, and reducing formation of 43S complexes, thereby favouring translation of viral mRNAs.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4106463/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉 〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4106463/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hashem, Yaser -- des Georges, Amedee -- Dhote, Vidya -- Langlois, Robert -- Liao, Hstau Y -- Grassucci, Robert A -- Pestova, Tatyana V -- Hellen, Christopher U T -- Frank, Joachim -- R01 AI51340/AI/NIAID NIH HHS/ -- R01 GM029169/GM/NIGMS NIH HHS/ -- R01 GM59660/GM/NIGMS NIH HHS/ -- R01GM29169/GM/NIGMS NIH HHS/ -- Howard Hughes Medical Institute/ -- England -- Nature. 2013 Nov 28;503(7477):539-43. doi: 10.1038/nature12658. Epub 2013 Nov 3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉1] Howard Hughes Medical Institute (HHMI), Department of Biochemistry and Molecular Biophysics, Columbia University, New York City, New York 10032, USA [2] Department of Biochemistry and Molecular Biophysics, Columbia University, New York City, New York 10032, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24185006" target="_blank"〉PubMed〈/a〉
Keywords:
Animals
;
Binding, Competitive
;
Classical swine fever virus/*genetics
;
Cryoelectron Microscopy
;
Eukaryotic Initiation Factor-3/chemistry/*metabolism/ultrastructure
;
Humans
;
Models, Molecular
;
Protein Biosynthesis
;
RNA, Viral/*genetics/*metabolism
;
Rabbits
;
Regulatory Sequences, Ribonucleic Acid/*genetics
;
Ribosome Subunits, Small, Eukaryotic/chemistry/*metabolism/ultrastructure
;
Ribosomes/chemistry/*metabolism/ultrastructure
Print ISSN:
0028-0836
Electronic ISSN:
1476-4687
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
,
Natural Sciences in General
,
Physics
Permalink
