Mutations in GCD11, the structural gene for eIF-2 gamma in yeast, alter translational regulation of GCN4 and the selection of the start site for protein synthesis.

Dorris, David; Erickson, F. Les; Hannig, Ernest M.

doi:10.1002/j.1460-2075.1995.tb07218.x

Cited by 63 publications

(73 citation statements)

References 65 publications

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“…Mutation to a larger residue would be predicted to result in a steric clash with the ribose of A76 of the tRNA. Fortuitously, the yeast eIF2␥ Gly 397 to Ala mutation was isolated previously as a mutant that derepresses GCN4 mRNA translation (gcd11-507 mutation) (32). The eIF2␥-G397A mutation causes a modest slow growth phenotype (32), and here we show that this slow growth phenotype can be fully suppressed by overexpression of Met- Fig.…”

Section: Molecular Modeling and Functional Identification Of The Mettsupporting

confidence: 52%

X-ray Structure of Translation Initiation Factor eIF2γ

Roll-Mecak

Alone

Cao

et al. 2004

Journal of Biological Chemistry

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The x-ray structure of the ␥-subunit of the heterotrimeric translation initiation factor eIF2 has been determined to 2.4-Å resolution. eIF2 is a GTPase that delivers the initiator Met-tRNA to the P site on the small ribosomal subunit during a rate-limiting initiation step in translation. The structure of eIF2␥ closely resembles that of EF1A⅐GTP, consisting of an N-terminal G domain followed by two ␤-barrels arranged in a closed configuration with domain II packed against the G domain in the vicinity of the Switch regions. The G domain of eIF2␥ has an unusual zinc ribbon motif, not previously found in other GTPases. Structure-based site-directed mutagenesis was used to identify two adjacent features on the surface of eIF2␥ that bind the ␣-subunit and Met-tRNA i Met , respectively. These structural, biochemical, and genetic results provide new insights into eIF2 ternary complex assembly.Translation initiation involves assembly of a large protein-RNA complex at the initiation codon of a mRNA in three main steps: binding of initiator Met-tRNA and mRNA with associated factors to the small ribosomal subunit, pairing of the anticodon of Met-tRNA i Met with the AUG start codon, and joining of the two ribosomal subunits to form the 80 S initiation complex. In eukaryotes, this process requires at least twelve distinct translation initiation factors (eIFs) 1 and hydrolysis of two molecules of GTP (reviewed in Ref. 1). Translation initiation factor eIF2 is a heterotrimeric GTPase that delivers the Met-tRNA i Met to the small ribosomal subunit as part of a ternary complex with GTP. Pairing between the anticodon of the Met-tRNA i Met and the AUG start codon triggers hydrolysis of GTP by eIF2 and eIF2⅐GDP is released, leaving Met-tRNA i Met bound in the P site. eIF2⅐GDP cannot bind Met-tRNA i Met and is converted to eIF2⅐GTP by the heteropentameric exchange fac-eIF2 is a stable complex of three subunits (␣, ␤, and ␥), each essential for viability in yeast. Since their discovery, highly conserved eIF2 subunits have been identified in all eukaryotes (reviewed in Ref.2) and also archaebacteria (3). Biochemical and genetic analyses have demonstrated that the three subunits have distinct activities during translation initiation. The ␥-subunit binds GTP and Met-tRNA i Met (reviewed in Ref. 4). GTP hydrolysis by the eIF2 ternary complex bound to the 40 S ribosomal subunit is stimulated by eIF5, which interacts with eIF2␤ (5). The ␤-subunit also interacts with Met-tRNA i Met and has been reported to bind mRNA (6). Given the pivotal role eIF2 plays in eukaryotic translation initiation, it is not surprising that it represents an important target for regulation. In response to various environmental stressors (viral infection, amino acid starvation, heme deficiency, ER stress etc), the ␣-subunit is phosphorylated on Ser 51 , abolishing translation initiation by preventing eIF2B catalyzed GDP-GTP exchange.The ␥-subunit of eIF2 belongs to the superfamily of GTPbinding proteins and is most closely related to the translation elongation factor...

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Section: Molecular Modeling and Functional Identification Of The Mettsupporting

confidence: 52%

X-ray Structure of Translation Initiation Factor eIF2γ

Roll-Mecak

Alone

Cao

et al. 2004

Journal of Biological Chemistry

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“…Interestingly, mutations in eIF2g were independently isolated in a screen for Sui 2 mutants (Huang et al 1997). Consistent with these findings, the GCD11-R510H mutant, originally isolated based on its ability to derepress GCN4 expression, also confers a Sui 2 phenotype (Dorris et al 1995). The eIF2g protein consists of three domains: an N-terminal GTP binding domain and b-barrel domains II and III ( Figure 3A).…”

Section: Ternary Complex Formationmentioning

confidence: 65%

“…The structure of Phe-tRNA bound to EF-Tu revealed that the amino acid and acceptor stem of the tRNA bind in a pocket formed between the G domain and domain II. Supporting the notion that eIF2g uses a similar pocket for Met-tRNA i Met binding, the slow-growth phenotype of the gcd11-Y142H mutant, which alters a residue in the proposed Met-tRNA i Met binding pocket, was partially suppressed by overexpression of tRNA i Met , and purified eIF2 complexes containing the mutant eIF2g subunit showed defects in Met-tRNA i Met binding (Dorris et al 1995;Erickson and Hannig 1996;Shin et al 2011). Thus, at least the acceptor stem and amino acid binding site appears to be shared between eIF2 and EF-Tu.…”

Section: Ternary Complex Formationmentioning

confidence: 87%

Mechanism and Regulation of Protein Synthesis in Saccharomyces cerevisiae

2016

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In this review, we provide an overview of protein synthesis in the yeast Saccharomyces cerevisiae. The mechanism of protein synthesis is well conserved between yeast and other eukaryotes, and molecular genetic studies in budding yeast have provided critical insights into the fundamental process of translation as well as its regulation. The review focuses on the initiation and elongation phases of protein synthesis with descriptions of the roles of translation initiation and elongation factors that assist the ribosome in binding the messenger RNA (mRNA), selecting the start codon, and synthesizing the polypeptide. We also examine mechanisms of translational control highlighting the mRNA cap-binding proteins and the regulation of GCN4 and CPA1 mRNAs.

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“…Indeed, two mutations in Sw1 have been identified in yeast that cause defects in the function of eIF2 (10,19), further emphasizing importance of Sw1. However, it has not been evident whether Sw1 in the ␥-subunit is actually involved in ligand binding as in EF1A.…”

Section: Structural Change Of Sw1mentioning

confidence: 99%

Structure of archaeal translational initiation factor 2 βγ–GDP reveals significant conformational change of the β-subunit and switch 1 region

Sokabe

Yao

Sakai

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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Archaeal͞eukaryotic initiation factor 2 (a͞eIF2) consists of ␣-, ␤-, and ␥-subunits and delivers initiator methionine tRNA (Met-tRNAi) to a small ribosomal subunit in a GTP-dependent manner. The structures of the aIF2␤␥ (archaeal initiation factor 2 ␤␥) heterodimeric complex in the apo and GDP forms were analyzed at 2.8-and 3.4-Å resolution, respectively. The results showed that the N-terminal helix and the central helix-turn-helix domain of the ␤-subunit bind to the G domain of the ␥-subunit but are distant from domains 2 and 3, to which the ␣-subunit and Met-tRNAi bind. This result is consistent with most of the previous analyses of eukaryotic factors, and thus indicates that the binding mode is essentially conserved among a͞eIF2. Comparison with the uncomplexed structure showed significant differences between the two forms of the ␤-subunit, particularly the C-terminal zinc-binding domain, which does not interact with the ␥-subunit and was suggested previously to be involved in GTP hydrolysis. Furthermore, the switch 1 region in the ␥-subunit, which is shown to be responsible for Met-tRNA i binding by mutational analysis, is moved away from the nucleotide through the interaction with highly conserved R87 in the ␤-subunit. These results implicate that conformational change of the ␤-subunit facilitates GTP hydrolysis by inducing the conformational change of the switch 1 region toward the off state.initiator methionine tRNA ͉ ribosome

show abstract

Mutations in GCD11, the structural gene for eIF-2 gamma in yeast, alter translational regulation of GCN4 and the selection of the start site for protein synthesis.

Cited by 63 publications

References 65 publications

X-ray Structure of Translation Initiation Factor eIF2γ

X-ray Structure of Translation Initiation Factor eIF2γ

Mechanism and Regulation of Protein Synthesis in Saccharomyces cerevisiae

Structure of archaeal translational initiation factor 2 βγ–GDP reveals significant conformational change of the β-subunit and switch 1 region

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