Open AccessFactor-dependent processivity in human eIF4A DEAD-box helicase
Author(s) -
Cuauhtémoc Garcı́a-Garcı́a,
Kirsten L. Frieda,
Kateryna Feoktistova,
Christopher S. Fraser,
Steven M. Block
Publication year - 2015
Publication title -
science
Language(s) - Uncategorized
Resource type - Journals
SCImago Journal Rank - 12.556
H-Index - 1186
eISSN - 1095-9203
pISSN - 0036-8075
DOI - 10.1126/science.aaa5089
Subject(s) - eif4a , initiation factor , rna , eukaryotic translation , helicase , rna helicase a , ribosome , biology , translation (biology) , messenger rna , processivity , genetics , microbiology and biotechnology , physics , computational biology , dna , polymerase , gene
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.
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