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RNA BIOCHEMISTRY. Factor-dependent processivity in human eIF4A DEAD-box helicase
Cuauhtémoc García-García1, Kirsten L Frieda2, Kateryna Feoktistova3
1Department of Biology, Stanford University, Stanford, CA 94305, USA.
Science (New York, N.Y.)
|June 27, 2015
Summary
Eukaryotic translation initiation factor 4A (eIF4A) acts as a processive helicase, not nonprocessive, when aided by eIF4G and eIF4B. This reveals a stepwise mechanism for mRNA scanning during translation.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- Eukaryotic translation initiation involves scanning mRNA for the start codon, powered by eukaryotic initiation factor 4A (eIF4A), a DEAD-box helicase.
- eIF4A was previously believed to unwind 5' untranslated region structures through a nonprocessive mechanism.
Purpose of the Study:
- To investigate the mechanism of eIF4A in eukaryotic translation initiation.
- To determine if eIF4A exhibits processivity when interacting with accessory factors.
Main Methods:
- Utilized a single-molecule assay to observe eIF4A activity.
- Analyzed the translocation steps of eIF4A in the presence of eIF4G and eIF4B.
Main Results:
- eIF4A functions as an adenosine triphosphate-dependent processive helicase when complexed with eIF4G and eIF4B.
- Translocation occurred in discrete steps of 11 ± 2 base pairs, independent of accessory factor combinations.
Conclusions:
- Findings support a memory-less stepwise mechanism for translation initiation.
- Suggests that factor-dependent processivity may be a conserved mechanism among DEAD-box helicases.
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