The largest of the mammalian translation initiation factors, eIF3, consists of at least eight subunits ranging in mass from 35 to 170kDa. eIF3 binds to the 40 S ribosome in an early step of translation initiation and promotes the binding of methionyl-tRNAi and mRNA []. The N-terminal domain of eukaryotic translation initiation factor 3 subunit C mediates eIF3 binding to eIF1 and eIF5 [].
eIF1/SUI1 (eukaryotic initiation factor 1) plays an important role in accurate initiator codon recognition during translation initiation. eIF1 interacts with 18S rRNA in the 40S ribosomal subunitduring eukaryotic translation initiation. Point mutations in the yeast eIF1 implicate the protein in maintaining accurate start-site selection but its mechanism of action is unknown [].Cells have evolved elaborate mechanisms to rid themselves of aberrant proteins and transcripts. The nonsense-mediated mRNA decay pathway (NMD) is an example of a pathway that eliminates aberrant mRNAs. In addition to its role in recognition of the AUG codon during translation initiation and maintenance of the appropriate reading frame during translation elongation by directing the ribosome to the proper start site of translation by functioning in concert with eIF-2 and the initiator tRNA-Met, the SUI1 protein plays a role in the NMD pathway [].
Eukaryotic translation initiation factor 3 subunit C (EIF3C) is a component of the eukaryotic translation initiation factor 3 (eIF-3) complex, which is required for several steps in the initiation of protein synthesis. EIF3C appears to be important for eIF3 activity []. Its N-terminal domain mediates eIF3 binding to eIF1 and eIF5 [], and its C-terminal PCI domain forms an important intermolecular bridge between eIF3 and the 40S ribosome [].
