Function of eukaryotic translation initiation factor 1A (eIF1A) (formerly called eIF-4C) in initiation of protein synthesis.
We have used an efficient in vitro translation initiation system to show that the mammalian 17-kDa eukaryotic initiation factor, eIF1A (formerly designated eIF-4C), is essential for transfer of the initiator Met-tRNAf (as Met-tRNAf.eIF2.GTP ternary complex) to 40 S ribosomal subunits in the absence of mRNA to form the 40 S preinitiation complex (40 S.Met-tRNAf.eIF2.GTP). Furthermore, eIF1A acted catalytically in this reaction to mediate highly efficient transfer of the Met-tRNAf.eIF2.GTP ternary complex to 40 S ribosomal subunits. The 40 S complex formed was free of eIF1A indicating that its role in 40 S preinitiation complex formation is not to stabilize the binding of Met-tRNAf to 40 S ribosomes. Additionally, the eIF1A-mediated 40 S initiation complex formed in the presence of AUG codon efficiently joined 60 S ribosomal subunits in an eIF5-dependent reaction to form a functional 80 S initiation complex. In contrast to other reports, we found that eIF1A plays no role either in the subunit joining reaction or in the generation of ribosomal subunits from 80 S ribosomes. Our results indicate that the major function of eIF1A is to mediate the transfer of Met-tRNAf to 40 S ribosomal subunits to form the 40 S preinitiation complex.
Chaudhuri
J
J
Department of Developmental and Molecular Biology, Albert Einstein College of Medicine of Yeshiva University, Bronx, New York 10461, USA.
Si
K
K
Maitra
U
U
D000818:Animals; D001665:Binding Sites; D002384:Catalysis; D003062:Codon; D015977:Eukaryotic Initiation Factor-1; D010442:Peptide Chain Initiation, Translational; D010448:Peptide Initiation Factors / Q000378:metabolism*; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism; D012358:RNA, Transfer, Met / Q000378:metabolism; D011817:Rabbits; D012270:Ribosomes / Q000378:metabolism
D003062:Codon; D015977:Eukaryotic Initiation Factor-1; D010448:Peptide Initiation Factors; D012333:RNA, Messenger; D012358:RNA, Transfer, Met; C026022:eukaryotic peptide initiation factor-1A