Spectrin domain of eukaryotic initiation factor 3a is the docking site for formation of the a:b:i:g subcomplex.
eIF3a (eukaryotic translation initiation factor 3a), one of the core subunits of the eIF3 complex, has been implicated in regulating translation of different mRNAs and in tumorigenesis. A subcomplex consisting of eIF3a, eIF3b, eIF3g, and eIF3i (eIF3(a:b:i:g)) has also been identified. However, how eIF3a participates in translational regulation and in formation of the eIF3(a:b:i:g) subcomplex remain to be solved. In this study, we used the tandem affinity purification approach in combination with tandem MS/MS and identified the spectrin domain of eIF3a as the docking site for the formation of eIF3(a:b:i:g) subcomplex. Although eIF3b and eIF3i bind concurrently to the spectrin domain of eIF3a within ∼10-15 amino acids apart, eIF3g binds to eIF3a indirectly via binding to the carboxyl-terminal domain of eIF3b. The binding of eIF3b to the spectrin domain of eIF3a occurs in its RNA recognition motif domain where eIF3j also binds in a mutually exclusive manner. Together, we conclude that the spectrin domain of eIF3a is responsible for the formation of eIF3(a:b:i:g) subcomplex and, because of mutually exclusive nature of bindings of eIF3a and eIF3j to eIF3b, different subcomplexes of eIF3 likely exist and may perform noncanonical functions in translational regulation.
From the Department of Pharmacology and Toxicology and Indiana University Simon Cancer Center, Indiana University School of Medicine, Indianapolis, Indiana 46202.
Zizheng
Z
Dong
Jing
J
Qi
Hui
H
Peng
Jianguo
J
Liu
Jian-Ting
JT
Zhang
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001665:Binding Sites; D039621:Eukaryotic Initiation Factor-3 / Q000737:chemistry*; D017353:Gene Deletion; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009154:Mutation; D011485:Protein Binding; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D040901:Proteomics / Q000379:methods; D012313:RNA / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D013049:Spectrin / Q000737:chemistry*; D053719:Tandem Mass Spectrometry
D039621:Eukaryotic Initiation Factor-3; D013049:Spectrin; D012313:RNA
Mass Spectrometry (MS); Protein-protein Interactions; Proteomics; TAP Purification; Translation Control; Translation Initiation Factors