Multiple roles for the C-terminal domain of eIF5 in translation initiation complex assembly and GTPase activation.
eIF5 stimulates the GTPase activity of eIF2 bound to Met-tRNA(i)(Met), and its C-terminal domain (eIF5-CTD) bridges interaction between eIF2 and eIF3/eIF1 in a multifactor complex containing Met-tRNA(i)(Met). The tif5-7A mutation in eIF5-CTD, which destabilizes the multifactor complex in vivo, reduced the binding of Met-tRNA(i)(Met) and mRNA to 40S subunits in vitro. Interestingly, eIF5-CTD bound simultaneously to the eIF4G subunit of the cap-binding complex and the NIP1 subunit of eIF3. These interactions may enhance association of eIF4G with eIF3 to promote mRNA binding to the ribosome. In vivo, tif5-7A eliminated eIF5 as a stable component of the pre-initiation complex and led to accumulation of 48S complexes containing eIF2; thus, conversion of 48S to 80S complexes is the rate-limiting defect in this mutant. We propose that eIF5-CTD stimulates binding of Met-tRNA(i)(Met) and mRNA to 40S subunits through interactions with eIF2, eIF3 and eIF4G; however, its most important function is to anchor eIF5 to other components of the 48S complex in a manner required to couple GTP hydrolysis to AUG recognition during the scanning phase of initiation.
Asano
K
K
Laboratory of Gene Regulation and Development, National Institute of Child Health and Human Development/NIH, Bethesda, MD 20892, USA.
Shalev
A
A
Phan
L
L
Nielsen
K
K
Clayton
J
J
Valásek
L
L
Donahue
T F
TF
Hinnebusch
A G
AG
D018387:Codon, Initiator / Q000378:metabolism; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism; D039621:Eukaryotic Initiation Factor-3; D039603:Eukaryotic Initiation Factor-4G; D040061:Eukaryotic Initiation Factor-5; D005656:Fungal Proteins / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D046911:Macromolecular Substances; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism; D010448:Peptide Initiation Factors / Q000235:genetics / Q000378:metabolism*; D011061:Poly A / Q000378:metabolism; D039665:Prokaryotic Initiation Factor-3; D011485:Protein Binding / Q000502:physiology; D014176:Protein Biosynthesis / Q000502:physiology*; D017434:Protein Structure, Tertiary / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D012358:RNA, Transfer, Met / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins
D018387:Codon, Initiator; D015852:Eukaryotic Initiation Factor-2; D039621:Eukaryotic Initiation Factor-3; D039603:Eukaryotic Initiation Factor-4G; D040061:Eukaryotic Initiation Factor-5; D005656:Fungal Proteins; D046911:Macromolecular Substances; C112736:Met-tRNA(i)(Met); C077915:NIP1 protein, S cerevisiae; D009687:Nuclear Proteins; D010448:Peptide Initiation Factors; D039665:Prokaryotic Initiation Factor-3; D012333:RNA, Messenger; D012358:RNA, Transfer, Met; D029701:Saccharomyces cerevisiae Proteins; D011061:Poly A; D006160:Guanosine Triphosphate; D020558:GTP Phosphohydrolases