Novel characteristics of the biological properties of the yeast Saccharomyces cerevisiae eukaryotic initiation factor 2A

Anton A. Komar, Stephane R. Gross, Diane Barth-Baus, Ryan Strachan, Jack O. Hensold, Terri G. Kinzy, William C. Merrick

Research output: Contribution to journalArticlepeer-review


Eukaryotic initiation factor 2A (eIF2A) has been shown to direct binding of the initiator methionyl-tRNA (Met-tRNA(i)) to 40 S ribosomal subunits in a codon-dependent manner, in contrast to eIF2, which requires GTP but not the AUG codon to bind initiator tRNA to 40 S subunits. We show here that yeast eIF2A genetically interacts with initiation factor eIF4E, suggesting that both proteins function in the same pathway. The double eIF2A/eIF4E-ts mutant strain displays a severe slow growth phenotype, which correlated with the accumulation of 85% of the double mutant cells arrested at the G(2)/M border. These cells also exhibited a disorganized actin cytoskeleton and elevated actin levels, suggesting that eIF2A might be involved in controlling the expression of genes involved in morphogenic processes. Further insights into eIF2A function were gained from the studies of eIF2A distribution in ribosomal fractions obtained from either an eIF5BDelta (fun12Delta) strain or a eIF3b-ts (prt1-1) strain. It was found that the binding of eIF2A to 40 and 80 S ribosomes was not impaired in either strain. We also found that eIF2A functions as a suppressor of Ure2p internal ribosome entry site-mediated translation in yeast cells. The regulation of expression from the URE2 internal ribosome entry site appears to be through the levels of eIF2A protein, which has been found to be inherently unstable with a half-life of approximately 17 min. It was hypothesized that this instability allows for translational control through the level of eIF2A protein in yeast cells.
Original languageEnglish
Pages (from-to)15601-15611
Number of pages11
JournalJournal of Biological Chemistry
Publication statusPublished - 22 Apr 2005

Bibliographical note

© 2005 The American Society for Biochemistry and Molecular Biology, Inc.


  • Eukaryotic initiation factor 2A
  • eIF2A
  • methionyl-tRNA (Met-tRNA(i))
  • S ribosomal subunits
  • codon-dependance
  • eIF2
  • GTP
  • AUG codon
  • tRNA
  • yeast eIF2A
  • initiation factor eIF4E
  • double eIF2A/eIF4E-ts mutant strain
  • growth phenotype
  • disorganized actin cytoskeleton
  • actin levels
  • morphogenic processes
  • ribosomal fractions
  • eIF5BDelta
  • fun12Delta
  • eIF3b-ts (prt1-1)
  • strain
  • Ure2p internal ribosome
  • yeast


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