Identification of a Translation Initiation Factor 3 (eIF3) Core Complex, Conserved in Yeast and Mammals, That Interacts with eIF5
AUTOR(ES)
Phan, Lon
FONTE
American Society for Microbiology
RESUMO
Only five of the nine subunits of human eukaryotic translation initiation factor 3 (eIF3) have recognizable homologs encoded in the Saccharomyces cerevisiae genome, and only two of these (Prt1p and Tif34p) were identified previously as subunits of yeast eIF3. We purified a polyhistidine-tagged form of Prt1p (His-Prt1p) by Ni2+ affinity and gel filtration chromatography and obtained a complex of ≈600 kDa composed of six polypeptides whose copurification was completely dependent on the polyhistidine tag on His-Prt1p. All five polypeptides associated with His-Prt1p were identified by mass spectrometry, and four were found to be the other putative homologs of human eIF3 subunits encoded in S. cerevisiae: YBR079c/Tif32p, Nip1p, Tif34p, and YDR429c/Tif35p. The fifth Prt1p-associated protein was eIF5, an initiation factor not previously known to interact with eIF3. The purified complex could rescue Met-tRNAiMet binding to 40S ribosomes in defective extracts from a prt1 mutant or extracts from which Nip1p had been depleted, indicating that it possesses a known biochemical activity of eIF3. These findings suggest that Tif32p, Nip1p, Prt1p, Tif34p, and Tif35p comprise an eIF3 core complex, conserved between yeast and mammals, that stably interacts with eIF5. Nip1p bound to eIF5 in yeast two-hybrid and in vitro protein binding assays. Interestingly, Sui1p also interacts with Nip1p, and both eIF5 and Sui1p have been implicated in accurate recognition of the AUG start codon. Thus, eIF5 and Sui1p may be recruited to the 40S ribosomes through physical interactions with the Nip1p subunit of eIF3.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=109077Documentos Relacionados
- Interactions of Eukaryotic Translation Initiation Factor 3 (eIF3) Subunit NIP1/c with eIF1 and eIF5 Promote Preinitiation Complex Assembly and Regulate Start Codon Selection
- Cloning and characterization of the p42 subunit of mammalian translation initiation factor 3 (eIF3): demonstration that eIF3 interacts with eIF5 in mammalian cells.
- Mutational Analysis of Mammalian Translation Initiation Factor 5 (eIF5): Role of Interaction between the β Subunit of eIF2 and eIF5 in eIF5 Function In Vitro and In Vivo
- The Yeast Eukaryotic Initiation Factor 4G (eIF4G) HEAT Domain Interacts with eIF1 and eIF5 and Is Involved in Stringent AUG Selection
- Multiple roles for the C-terminal domain of eIF5 in translation initiation complex assembly and GTPase activation