Dataset Information

Dynamic Interaction of Eukaryotic Initiation Factor 4G1 (eIF4G1) with eIF4E and eIF1 Underlies Scanning-Dependent and -Independent Translation.

ABSTRACT: Translation initiation of most mRNAs involves m7G-cap binding, ribosomal scanning, and AUG selection. Initiation from an m7G-cap-proximal AUG can be bypassed resulting in leaky scanning, except for mRNAs bearing the translation initiator of short 5' untranslated region (TISU) element. m7G-cap binding is mediated by the eukaryotic initiation factor 4E (eIF4E)-eIF4G1 complex. eIF4G1 also associates with eIF1, and both promote scanning and AUG selection. Understanding of the dynamics and significance of these interactions is lacking. We report that eIF4G1 exists in two complexes, either with eIF4E or with eIF1. Using an eIF1 mutant impaired in eIF4G1 binding, we demonstrate that eIF1-eIF4G1 interaction is important for leaky scanning and for avoiding m7G-cap-proximal initiation. Intriguingly, eIF4E-eIF4G1 antagonizes the scanning promoted by eIF1-eIF4G1 and is required for TISU. In mapping the eIF1-binding site on eIF4G1, we unexpectedly found that eIF4E also binds it indirectly. These findings uncover the RNA features underlying regulation by eIF4E-eIF4G1 and eIF1-eIF4G1 and suggest that 43S ribosome transition from the m7G-cap to scanning involves relocation of eIF4G1 from eIF4E to eIF1.

SUBMITTER: Haimov O

PROVIDER: S-EPMC6113598 | biostudies-literature | 2018 Sep

REPOSITORIES: biostudies-literature

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Publications

Dynamic Interaction of Eukaryotic Initiation Factor 4G1 (eIF4G1) with eIF4E and eIF1 Underlies Scanning-Dependent and -Independent Translation.

Haimov Ora O Sehrawat Urmila U Tamarkin-Ben Harush Ana A Bahat Anat A Uzonyi Anna A Will Alexander A Hiraishi Hiroyuki H Asano Katsura K Dikstein Rivka R

Molecular and cellular biology 20180828 18

Translation initiation of most mRNAs involves m7G-cap binding, ribosomal scanning, and AUG selection. Initiation from an m7G-cap-proximal AUG can be bypassed resulting in leaky scanning, except for mRNAs bearing the translation initiator of short 5' untranslated region (TISU) element. m7G-cap binding is mediated by the eukaryotic initiation factor 4E (eIF4E)-eIF4G1 complex. eIF4G1 also associates with eIF1, and both promote scanning and AUG selection. Understanding of ...[more]

PMID: 29987188

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Project description:Ischemic strokes are caused by a reduction in cerebral blood flow and both the ischemic period and subsequent reperfusion induce brain injury, with different tissue damage depending on the severity of the ischemic insult, its duration, and the particular areas of the brain affected. In those areas vulnerable to cerebral ischemia, the inhibition of protein translation is an essential process of the cellular response leading to delayed neuronal death. In particular, translation initiation is rate-limiting for protein synthesis and the eukaryotic initiation factor (eIF) 4F complex is indispensable for cap-dependent protein translation. In the eIF4F complex, eIF4G is a scaffolding protein that provides docking sites for the assembly of eIF4A and eIF4E, binding to the cap structure of the mRNA and stabilizing all proteins of the complex. The eIF4F complex constituents, eIF4A, eIF4E, and eIF4G, participate in translation regulation by their phosphorylation at specific sites under cellular stress conditions, modulating the activity of the cap-binding complex and protein translation. This work investigates the phosphorylation of eIF4G1 involved in the eIF4E/eIF4G1 association complex, and their regulation in ischemia-reperfusion (IR) as a stress-inducing condition. IR was induced in an animal model of transient cerebral ischemia and the results were studied in the resistant cortical region and in the vulnerable hippocampal CA1 region. The presented data demonstrate the phosphorylation of eIF4G1 at Ser1147, Ser1185, and Ser1231 in both brain regions and in control and ischemic conditions, being the phosphorylation of eIF4G1 at Ser1147 the only one found in the eIF4E/eIF4G association complex from the cap-containing matrix (m7GTP-Sepharose). In addition, our work reveals the specific modulation of the phosphorylation of eIF4G1 at Ser1147 in the vulnerable region, with increased levels and colocalization with eIF4E in response to IR. These findings contribute to elucidate the molecular mechanism of protein translation regulation that underlies in the balance of cell survival/death during pathophysiological stress, such as cerebral ischemia.

Dataset Information

Dynamic Interaction of Eukaryotic Initiation Factor 4G1 (eIF4G1) with eIF4E and eIF1 Underlies Scanning-Dependent and -Independent Translation.

Publications

Dynamic Interaction of Eukaryotic Initiation Factor 4G1 (eIF4G1) with eIF4E and eIF1 Underlies Scanning-Dependent and -Independent Translation.

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