NDLI: Tight Binding of the Phosphorylated α Subunit of Initiation Factor 2 (eIF2α) to the Regulatory Subunits of Guanine Nucleotide Exchange Factor eIF2B Is Required for Inhibition of Translation Initiation

Content Provider	PubMed Central
Author	Krishnamoorthy, Thanuja Pavitt, Graham D. Zhang, Fan Dever, Thomas E. Hinnebusch, Alan G.
Copyright Year	2001
Abstract	Translation initiation factor 2 (eIF2) is a heterotrimeric protein that transfers methionyl-initiator tRNAMet to the small ribosomal subunit in a ternary complex with GTP. The eIF2 phosphorylated on serine 51 of its α subunit [eIF2(αP)] acts as competitive inhibitor of its guanine nucleotide exchange factor, eIF2B, impairing formation of the ternary complex and thereby inhibiting translation initiation. eIF2B is comprised of catalytic and regulatory subcomplexes harboring independent eIF2 binding sites; however, it was unknown whether the α subunit of eIF2 directly contacts any eIF2B subunits or whether this interaction is modulated by phosphorylation. We found that recombinant eIF2α (glutathione S-transferase [GST]–SUI2) bound to the eIF2B regulatory subcomplex in vitro, in a manner stimulated by Ser-51 phosphorylation. Genetic data suggest that this direct interaction also occurred in vivo, allowing overexpressed SUI2 to compete with eIF2(αP) holoprotein for binding to the eIF2B regulatory subcomplex. Mutations in SUI2 and in the eIF2B regulatory subunit GCD7 that eliminated inhibition of eIF2B by eIF2(αP) also impaired binding of phosphorylated GST-SUI2 to the eIF2B regulatory subunits. These findings provide strong evidence that tight binding of phosphorylated SUI2 to the eIF2B regulatory subcomplex is crucial for the inhibition of eIF2B and attendant downregulation of protein synthesis exerted by eIF2(αP). We propose that this regulatory interaction prevents association of the eIF2B catalytic subcomplex with the β and γ subunits of eIF2 in the manner required for GDP-GTP exchange.
Related Links	http://dx.doi.org/10.1128/mcb.21.15.5018-5030.2001
Ending Page	5030
Page Count	13
Starting Page	5018
File Format	PDF
ISSN	02707306
e-ISSN	10985549
Journal	Molecular and Cellular Biology
Issue Number	15
Volume Number	21
Language	English
Publisher	American Society for Microbiology
Publisher Date	2001-08-01
Access Restriction	Open
Rights Holder	American Society for Microbiology
Subject Keyword	Cell Biology Molecular Biology Research in Higher Education
Content Type	Text
Resource Type	Article
Subject	Cell Biology Molecular Biology

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