Mutations in <i>Caenorhabditis elegans</i> eIF2β Permit Translation Initiation From Non-AUG Start Codons

Zhang, Yinhua; Maduzia, Lisa L.

doi:10.1534/genetics.110.115485

Cited by 5 publications

(11 citation statements)

References 34 publications

(39 reference statements)

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“…Missense mutations in a conserved structural interface of eIF1 lead to expression of a non-AUG reporter: We have previously described a reporter system for isolating mutants that permits the use of non-AUG start codons in translation initiation (Zhang and Maduzia 2010). This reporter contains a GTG codon rather than an ATG codon at the start site of the GFP coding region.…”

Section: Resultsmentioning

confidence: 99%

“…Previously, we used genetic suppression experiments to demonstrate that the eIF2b mutant iftb-1(nb101) was able to initiate translation from endogenous mutant unc-62(t2012) mRNAs containing an AUA codon in place of its AUG start codon (Zhang and Maduzia 2010). We performed similar genetic suppression experiments with eif-1(nb132).…”

Section: Resultsmentioning

confidence: 99%

“…Mutant screen: Both eif-1(nb132) and eif-1(nb134) strains were isolated from a screen described previously (Zhang and Maduzia 2010). This screen mutagenized approximately 75,000 genomes with N-ethyl-N-nitrosourea (ENU) in a reporter strain carrying the integrated reporter transgene nbIs4.…”

Section: Methodsmentioning

confidence: 99%

“…GFP protein expressed from an identical number of worms for each mutant strain using Western blot analysis. Detailed procedures for determining GFP expression were described previously (Zhang and Maduzia 2010).…”

Section: Methodsmentioning

confidence: 99%

“…It is not known if there are similar mechanisms regulating translation initiation fidelity in multicellular organisms. To address this question, we designed a genetic system to isolate C. elegans mutants that have reduced fidelity in AUG start codon selection (Zhang and Maduzia 2010). Mutants were selected on the basis of their ability to express a GFP reporter that contains a GUG codon in place of its native translation start site.…”

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confidence: 99%

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The Role of eIF1 in Translation Initiation Codon Selection in Caenorhabditis elegans

et al. 2010

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The selection of a proper AUG start codon requires the base-pairing interactions between the codon on the mRNA and the anticodon of the initiator tRNA. This selection process occurs in a pre-initiation complex that includes multiple translation initiation factors and the small ribosomal subunit. To study how these initiation factors are involved in start codon recognition in multicellular organisms, we isolated mutants that allow the expression of a GFP reporter containing a non-AUG start codon. Here we describe the characterization of mutations in eif-1, which encodes the Caenorhabditis elegans translation initiation factor 1 (eIF1). Two mutations were identified, both of which are substitutions of amino acid residues that are identical in all eukaryotic eIF1 proteins. These residues are located in a structural region where the amino acid residues affected by the Saccharomyces cerevisiae eIF1 mutations are also localized. Both C. elegans mutations are dominant in conferring a non-AUG translation initiation phenotype and lead to growth arrest defects in homozygous animals. By assaying reporter constructs that have base changes at the AUG start codon, these mutants are found to allow expression from most reporters that carry single base changes within the AUG codon. This trend of non-AUG mediated initiation was also observed previously for C. elegans eIF2b mutants, indicating that these two factors play a similar role. These results support that eIF1 functions in ensuring the fidelity of AUG start codon recognition in a multicellular organism.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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confidence: 99%

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The Role of eIF1 in Translation Initiation Codon Selection in Caenorhabditis elegans

et al. 2010

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Repeat-Associated Non-AUG Translation and Its Impact in Neurodegenerative Disease

Kearse

Todd

2014

Neurotherapeutics

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Nucleotide repeat expansions underlie numerous human neurological disorders. Repeats can trigger toxicity through multiple pathogenic mechanisms, including RNA gain-of-function, protein gain-of-function, and protein loss-of-function pathways. Traditionally, inference of the underlying pathogenic mechanism derives from the repeat location, with dominantly inherited repeats within transcribed noncoding sequences eliciting toxicity predominantly as RNA via sequestration of specific RNA binding proteins. However, recent findings question this assumption and suggest that repeats outside of annotated open reading frames may also trigger toxicity through a novel form of protein translational initiation known as repeat-associated non-AUG (RAN) translation. To date, RAN translation has been implicated in 4 nucleotide repeat expansion disorders: spinocerebellar ataxia type 8; myotonic dystrophy type 1 with CTG•CAG repeats; C9orf72 amyotrophic lateral sclerosis/frontotemporal dementia with GGGGCC•GGCCCC repeats; and fragile X-associated tremor/ataxia syndrome with CGG repeats. RAN translation contributes to hallmark pathological characteristics in these disorders by producing homopolymeric or dipeptide repeat proteins. Here, we review what is known about RAN translation, with an emphasis on how differences in both repeat sequence and context may confer different requirements for unconventional initiation. We then discuss how this new mechanism of translational initiation might function in normal physiology and lay out a roadmap for addressing the numerous questions that remain.

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Structural basis of AUC codon discrimination during translation initiation in yeast

Villamayor-Belinchón,

Sharma,

Gordiyenko

et al. 2024

Nucleic Acids Research

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In eukaryotic translation initiation, the 48S preinitiation complex (PIC) scans the 5′ untranslated region of mRNAs to search for the cognate start codon (AUG) with assistance from various eukaryotic initiation factors (eIFs). Cognate start codon recognition is precise, rejecting near-cognate codons with a single base difference. However, the structural basis of discrimination of near-cognate start codons was not known. We have captured multiple yeast 48S PICs with a near-cognate AUC codon at the P-site, revealing that the AUC codon induces instability in the codon-anticodon at the P-site, leading to a disordered N-terminal tail of eIF1A. Following eIF1 dissociation, the N-terminal domain of eIF5 fails to occupy the vacant eIF1 position, and eIF2β becomes flexible. Consequently, 48S with an AUC codon is less favourable for initiation. Furthermore, we observe hitherto unreported metastable states of the eIF2-GTP-Met-tRNAMet ternary complex, where the eIF2β helix-turn-helix domain may facilitate eIF5 association by preventing eIF1 rebinding to 48S PIC. Finally, a swivelled head conformation of 48S PIC appears crucial for discriminating incorrect and selection of the correct codon-anticodon pair during translation initiation.

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Mutations in Caenorhabditis elegans eIF2β Permit Translation Initiation From Non-AUG Start Codons

Cited by 5 publications

References 34 publications

The Role of eIF1 in Translation Initiation Codon Selection in Caenorhabditis elegans

The Role of eIF1 in Translation Initiation Codon Selection in Caenorhabditis elegans

Repeat-Associated Non-AUG Translation and Its Impact in Neurodegenerative Disease

Structural basis of AUC codon discrimination during translation initiation in yeast

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