Abstract
eIF4A is a DEAD-box RNA-dependent ATPase thought to unwind RNA secondary structure in the 5'-untranslated regions (UTRs) of mRNAs to promote their recruitment to the eukaryotic translation pre-initiation complex (PIC). We show that eIF4A's ATPase activity is markedly stimulated in the presence of the PIC, independently of eIF4E•eIF4G, but dependent on subunits i and g of the heteromeric eIF3 complex. Surprisingly, eIF4A accelerated the rate of recruitment of all mRNAs tested, regardless of their degree of structural complexity. Structures in the 5'-UTR and 3' of the start codon synergistically inhibit mRNA recruitment in a manner relieved by eIF4A, indicating that the factor does not act solely to melt hairpins in 5'-UTRs. Our findings that eIF4A functionally interacts with the PIC and plays important roles beyond unwinding 5'-UTR structure is consistent with a recent proposal that eIF4A modulates the conformation of the 40S ribosomal subunit to promote mRNA recruitment.
Keywords:
RNA helicase; S. cerevisiae; biochemistry; biophysics; eIF4A; eIF4F; mRNA recruitment; ribosome; structural biology; translation initiation.
MeSH terms
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5' Untranslated Regions
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Adenosine Triphosphatases / genetics
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Adenosine Triphosphatases / metabolism
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Adenosine Triphosphate / metabolism
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Eukaryotic Initiation Factor-4E / genetics
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Eukaryotic Initiation Factor-4E / metabolism
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Eukaryotic Initiation Factor-4F / metabolism*
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Eukaryotic Initiation Factor-4G / genetics
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Eukaryotic Initiation Factor-4G / metabolism
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Protein Binding
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Protein Conformation
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RNA Helicases / metabolism*
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RNA, Fungal / chemistry*
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RNA, Fungal / genetics
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RNA, Fungal / metabolism
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RNA, Messenger / chemistry*
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RNA, Messenger / genetics
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RNA, Messenger / metabolism
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Ribosomal Proteins / genetics
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Ribosomal Proteins / metabolism
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Saccharomyces cerevisiae / genetics
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Saccharomyces cerevisiae / growth & development
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Saccharomyces cerevisiae / metabolism*
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Saccharomyces cerevisiae Proteins / genetics
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Saccharomyces cerevisiae Proteins / metabolism*
Substances
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5' Untranslated Regions
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Eukaryotic Initiation Factor-4E
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Eukaryotic Initiation Factor-4F
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Eukaryotic Initiation Factor-4G
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RNA, Fungal
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RNA, Messenger
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RPL41 protein, S cerevisiae
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Ribosomal Proteins
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Saccharomyces cerevisiae Proteins
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TIF4631 protein, S cerevisiae
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Adenosine Triphosphate
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Adenosine Triphosphatases
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RNA Helicases
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TIF1 protein, S cerevisiae
Grants and funding
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.