title: Translation initiation factors that function as RNA helicases from mammals, plants and yeast.
abstract: Ribosome binding to eukaryotic mRNAs requires the concerted action of three eukaryotic initiation factors: eIF-4A, eIF-4B and eIF-4F as well as the hydrolysis of ATP. These initiation factors are implicated in the unwinding of mRNA 5' secondary structure and have been isolated from mammals, yeast and wheat germ. We used an RNA unwinding assay to compare the activities of these factors from the different species. We also measured the inter-species interchangeability of these factors in the unwinding reaction. In mammals, it has been previously shown that a combination of rabbit reticulocyte eIF-4F and -4B or eIF-4A and -4B were active in the RNA unwinding assay. In wheat germ, the combination of eIF-4A and eIF-4F resulted in RNA unwinding in a reaction that was stimulated by eIF-4B. Mammalian eIF-4A was able to substitute in this system. We also show that yeast eIF-4A is able to effectively substitute for mammalian eIF-4A in duplex RNA unwinding in combination with mammalian eIF-4B, while wheat-germ eIF-4A was only partially able to substitute. Taken together, these results suggest that initiation factor requirements for RNA unwinding are largely similar in mammals, yeast and plants.
authors.affiliation: Department of Biochemistry, McGill University, Montreal, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Jaramillo
authors.forename: K
authors.initials: K
authors.lastname: Browning
authors.forename: T E
authors.initials: TE
authors.lastname: Dever
authors.forename: S
authors.initials: S
authors.lastname: Blum
authors.forename: H
authors.initials: H
authors.lastname: Trachsel
authors.forename: W C
authors.initials: WC
authors.lastname: Merrick
authors.forename: J M
authors.initials: JM
authors.lastname: Ravel
authors.forename: N
authors.initials: N
authors.lastname: Sonenberg
mesh_terms: D000818:Animals; D001483:Base Sequence; D004265:DNA Helicases / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D039601:Eukaryotic Initiation Factor-4A; D039562:Eukaryotic Initiation Factor-4F; D039642:Eukaryotic Initiation Factors; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010448:Peptide Initiation Factors / Q000302:isolation & purification / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011817:Rabbits; D012156:Reticulocytes / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic; D014908:Triticum / Q000235:genetics* / Q000378:metabolism; D014764:Viral Proteins
chemical_list: D004268:DNA-Binding Proteins; D039562:Eukaryotic Initiation Factor-4F; D039642:Eukaryotic Initiation Factors; D010448:Peptide Initiation Factors; D012333:RNA, Messenger; D014764:Viral Proteins; C031799:eIF-4B; C060035:gp32 protein, Enterobacteria phage T4; C027729:helix-destabilizing proteins; D039601:Eukaryotic Initiation Factor-4A; D004265:DNA Helicases