Mammalian translation initiation factor eIF1 functions with eIF1A and eIF3 in the formation of a stable 40 S preinitiation complex.
We have examined the role of the mammalian initiation factor eIF1 in the formation of the 40 S preinitiation complex using in vitro binding of initiator Met-tRNA (as Met-tRNA(i).eIF2.GTP ternary complex) to 40 S ribosomal subunits in the absence of mRNA. We observed that, although both eIF1A and eIF3 are essential to generate a stable 40 S preinitiation complex, quantitative binding of the ternary complex to 40 S subunits also required eIF1. The 40 S preinitiation complex contained, in addition to eIF3, both eIF1 and eIF1A in a 1:1 stoichiometry with respect to the bound Met-tRNA(i). These three initiation factors also bind to free 40 S subunits, and the resulting complex can act as an acceptor of the ternary complex to form the 40 S preinitiation complex (40 S.eIF3.eIF1.eIF1A.Met-tRNA(i).eIF2.GTP). The stable association of eIF1 with 40 S subunits required the presence of eIF3. In contrast, the binding of eIF1A to free 40 S ribosomes as well as to the 40 S preinitiation complex was stabilized by the presence of both eIF1 and eIF3. These studies suggest that it is possible for eIF1 and eIF1A to bind the 40 S preinitiation complex prior to mRNA binding.
Majumdar
Romit
R
Department of Developmental and Molecular Biology, Albert Einstein College of Medicine of Yeshiva University, Jack and Pearl Resnick Campus, Bronx, New York 10461, USA.
Bandyopadhyay
Amitabha
A
Maitra
Umadas
U
D000818:Animals; D015977:Eukaryotic Initiation Factor-1 / Q000302:isolation & purification / Q000378:metabolism*; D039621:Eukaryotic Initiation Factor-3 / Q000302:isolation & purification / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000378:metabolism; D010442:Peptide Chain Initiation, Translational / Q000502:physiology*; D010448:Peptide Initiation Factors / Q000302:isolation & purification / Q000378:metabolism*; D011485:Protein Binding; D012358:RNA, Transfer, Met / Q000378:metabolism*; D011817:Rabbits; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism
D015977:Eukaryotic Initiation Factor-1; D039621:Eukaryotic Initiation Factor-3; D010448:Peptide Initiation Factors; D012358:RNA, Transfer, Met; D011994:Recombinant Proteins; C026022:eukaryotic peptide initiation factor-1A; D006160:Guanosine Triphosphate