Domains of eIF1A that mediate binding to eIF2, eIF3 and eIF5B and promote ternary complex recruitment in vivo

AUTOR(ES)

Olsen, DeAnne S.

FONTE

Oxford University Press

RESUMO

Translation initiation factor 1A (eIF1A) is predicted to bind in the decoding site of the 40S ribosome and has been implicated in recruitment of the eIF2–GTP–Met-tRNAiMet ternary complex (TC) and ribosomal scanning. We show that the unstructured C-terminus of eIF1A interacts with the C-terminus of eIF5B, a factor that stimulates 40S–60S subunit joining, and removal of this domain of eIF1A diminishes translation initiation in vivo. These findings support the idea that eIF1A–eIF5B association is instrumental in releasing eIF1A from the ribosome after subunit joining. A larger C-terminal truncation that removes a 310 helix in eIF1A deregulates GCN4 translation in a manner suppressed by overexpressing TC, implicating eIF1A in TC binding to 40S ribosomes in vivo. The unstructured N-terminus of eIF1A interacts with eIF2 and eIF3 and is required at low temperatures for a step following TC recruitment. We propose a modular organization for eIF1A wherein a core ribosome-binding domain is flanked by flexible segments that mediate interactions with other factors involved in recruitment of TC and release of eIF1A at subunit joining.

Documentos Relacionados

• A multifactor complex of eukaryotic initiation factors, eIF1, eIF2, eIF3, eIF5, and initiator tRNAMet is an important translation initiation intermediate in vivo
• A subcomplex of three eIF3 subunits binds eIF1 and eIF5 and stimulates ribosome binding of mRNA and tRNAiMet
• Related eIF3 subunits TIF32 and HCR1 interact with an RNA recognition motif in PRT1 required for eIF3 integrity and ribosome binding
• The yeast eIF3 subunits TIF32/a, NIP1/c, and eIF5 make critical connections with the 40S ribosome in vivo
• Cloning and characterization of the p42 subunit of mammalian translation initiation factor 3 (eIF3): demonstration that eIF3 interacts with eIF5 in mammalian cells.