Fail-safe control of translation initiation by dissociation of eIF2α phosphorylated ternary complexes.
Phosphorylation of eIF2α controls translation initiation by restricting the levels of active eIF2-GTP/Met-tRNAi ternary complexes (TC). This modulates the expression of all eukaryotic mRNAs and contributes to the cellular integrated stress response. Key to controlling the activity of eIF2 are translation factors eIF2B and eIF5, thought to primarily function with eIF2-GDP and TC respectively. Using a steady-state kinetics approach with purified proteins we demonstrate that eIF2B binds to eIF2 with equal affinity irrespective of the presence or absence of competing guanine nucleotides. We show that eIF2B can compete with Met-tRNAi for eIF2-GTP and can destabilize TC. When TC is formed with unphosphorylated eIF2, eIF5 can out-compete eIF2B to stabilize TC/eIF5 complexes. However when TC/eIF5 is formed with phosphorylated eIF2, eIF2B outcompetes eIF5 and destabilizes TC. These data uncover competition between eIF2B and eIF5 for TC and identify that phosphorylated eIF2-GTP translation initiation intermediate complexes can be inhibited by eIF2B.
Division of Molecular and Cellular Function, Faculty of Biology Medicine and Health, The University of Manchester, Manchester, United Kingdom.|Manchester Academic Health Science Centre, The University of Manchester, Manchester, United Kingdom.
Martin D
MD
Jennings
Division of Molecular and Cellular Function, Faculty of Biology Medicine and Health, The University of Manchester, Manchester, United Kingdom.|Manchester Academic Health Science Centre, The University of Manchester, Manchester, United Kingdom.
Christopher J
CJ
Kershaw
Division of Molecular and Cellular Function, Faculty of Biology Medicine and Health, The University of Manchester, Manchester, United Kingdom.|Manchester Academic Health Science Centre, The University of Manchester, Manchester, United Kingdom.
Tomas
T
Adomavicius
Division of Molecular and Cellular Function, Faculty of Biology Medicine and Health, The University of Manchester, Manchester, United Kingdom.|Manchester Academic Health Science Centre, The University of Manchester, Manchester, United Kingdom.
Graham D
0000-0002-8593-2418
GD
Pavitt
D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism*; D020717:Eukaryotic Initiation Factor-2B / Q000378:metabolism*; D010442:Peptide Chain Initiation, Translational; D010448:Peptide Initiation Factors / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D012358:RNA, Transfer, Met / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D000097574:Eukaryotic Translation Initiation Factor 5A
D015852:Eukaryotic Initiation Factor-2; D020717:Eukaryotic Initiation Factor-2B; D010448:Peptide Initiation Factors; D012333:RNA, Messenger; D012358:RNA, Transfer, Met; D016601:RNA-Binding Proteins; D000097574:Eukaryotic Translation Initiation Factor 5A; C112736:Met-tRNA(i)(Met)
ISR; S. cerevisiae; biochemistry; chromosomes; eIF2; eIF2B; genes; protein interactions; translational control