Mammalian translation initiation factor eIF1 functions with eIF1A and eIF3 in the formation of a stable 40 S preinitiation complex

Romit Majumdar, Amitabha Bandyopadhyay, Umadas Maitra

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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-tRNAi·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-tRNAi. 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-tRNAi ·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.

Original languageEnglish (US)
Pages (from-to)6580-6587
Number of pages8
JournalJournal of Biological Chemistry
Issue number8
StatePublished - Feb 21 2003


ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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