RNA BIOCHEMISTRY. Factor-dependent processivity in human eIF4A DEAD-box helicase

During eukaryotic translation initiation, the small ribosomal subunit, assisted by initiation factors, locates the messenger RNA start codon by scanning from the 5' cap. This process is powered by the eukaryotic initiation factor 4A (eIF4A), a DEAD-box helicase. eIF4A has been thought to unwind...

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Published in:Science (American Association for the Advancement of Science) 2015-06, Vol.348 (6242), p.1486-1488
Main Authors: García-García, Cuauhtémoc, Frieda, Kirsten L, Feoktistova, Kateryna, Fraser, Christopher S, Block, Steven M
Format: Article
Language:English
Subjects:
Adenosine Triphosphate - chemistry
DNA - chemistry
Eukaryotic Initiation Factor-4A - chemistry
Eukaryotic Initiation Factor-4G - chemistry
Eukaryotic Initiation Factors - chemistry
Humans
Nucleic Acid Conformation
Protein Biosynthesis
RNA - chemistry
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Summary:During eukaryotic translation initiation, the small ribosomal subunit, assisted by initiation factors, locates the messenger RNA start codon by scanning from the 5' cap. This process is powered by the eukaryotic initiation factor 4A (eIF4A), a DEAD-box helicase. eIF4A has been thought to unwind structures formed in the untranslated 5' region via a nonprocessive mechanism. Using a single-molecule assay, we found that eIF4A functions instead as an adenosine triphosphate-dependent processive helicase when complexed with two accessory proteins, eIF4G and eIF4B. Translocation occurred in discrete steps of 11 ± 2 base pairs, irrespective of the accessory factor combination. Our findings support a memory-less stepwise mechanism for translation initiation and suggest that similar factor-dependent processivity may be shared by other members of the DEAD-box helicase family.
ISSN:1095-9203
DOI:10.1126/science.aaa5089