Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Translation initiation site profiling reveals widespread synthesis of non-AUG-initiated protein isoforms in yeast

ABSTRACT: Genomic analyses in budding yeast have helped to define the foundational principles of eukaryotic gene expression, but have systematically excluded specific classes of potential coding regions, including those with non-AUG start codons. Without methods to define coding regions empirically, the prevalence of these non-canonical coding regions has been impossible to assess. Here, we applied an experimental approach to globally annotate translation initiation sites in yeast and identified a class of 149 genes that encode N-terminally extended alternate protein isoforms that result from translation initiation at non-AUG codons upstream of the annotated AUG start codon. These alternate isoforms are produced in concert with canonical isoforms and are translated with a high degree of specificity, resulting from initiation at only a small subset of possible start codons in 5’ leader regions. Their translation is enriched during meiosis, and is induced by low eIF5A levels, which are observed in this context. These findings reveal widespread production of non-canonical protein isoforms and, more generally, show unexpected complexity to the rules by which the budding yeast genome is decoded.

ORGANISM(S): Saccharomyces cerevisiae

PROVIDER: GSE150375 | GEO | 2020/07/24

REPOSITORIES: GEO

ACCESS DATA

Json Xml

Similar Datasets

eIF1 discriminates against suboptimal initiation sites to prevent excessive uORF translation genome-wide

Project description:The translation pre-initiation complex (PIC) scans the mRNA for an AUG codon in favorable context. Previous findings suggest that the factor eIF1 discriminates against non-AUG start codons by impeding full accommodation of Met-tRNAi in the P site of the 40S ribosomal subunit, necessitating eIF1 dissociation for start codon selection. Consistent with this, yeast eIF1 substitutions that weaken its binding to the PIC increase initiation at UUG codons on a mutant his4 mRNA and particular synthetic mRNA reporters; and also at the AUG start codon of the mRNA for eIF1 itself owing to its poor Kozak context. It was not known however whether such eIF1 mutants increase initiation at suboptimal start codons genome-wide. By ribosome profiling, we show that the eIF1-L96P variant confers increased translation of numerous upstream open reading frames (uORFs) initiating with either near-cognate codons (NCCs) or AUGs in poor context. The increased uORF translation is frequently associated with reduced translation of the downstream main coding sequences (CDS). Initiation is also elevated at the NCCs initiating N-terminal extensions on GRS1 and ALA1 mRNAs, and at a small set of main CDS AUG codons with especially poor context, including that of eIF1 itself. Thus, eIF1 acts throughout the yeast translatome to discriminate against NCC start codons and AUGs in poor context; and impairing this function enhances the repressive effects of uORFs on CDS translation and alters the ratios of protein isoforms translated from near-cognate versus AUG start codons.

2019-10-18 | GSE138599 | GEO

Ribosome queuing enables non-AUG translation to be resistant to multiple protein synthesis inhibitors

Project description:Aberrant translation initiation at non-AUG start codons is associated with multiple cancers and neurodegenerative diseases. Nevertheless, how non-AUG translation is regulated differently from canonical translation is poorly understood. We thus used start codon-selective reporters and ribosome profiling to characterize how translation from non-AUG start codons responds to protein synthesis inhibitors in human cells. These analyses surprisingly revealed that translation of non-AUG reporters and the endogenous GUG-encoded DAP5 (eIF4G2/p97) mRNA are resistant to cycloheximide (CHX), a translation inhibitor which slows but does not completely abrogate elongation. Our data suggest that slowly elongating ribosomes cause queuing of scanning pre-initiation complexes (PIC), preferentially enhancing otherwise poor recognition of non-AUG start codons. Consistent with this model, limiting PIC formation or scanning sensitizes non-AUG translation to CHX. Moreover, PIC queuing can cause translation from an AUG codon in a poor context to become less sensitive to CHX. We further find that non-AUG translation is resistant to other inhibitors that target ribosomes within the coding sequence, but not those targeting newly initiated ribosomes. In total, these data indicate that ribosome queuing enables mRNAs with poor initiation context, namely those from non-AUG start codons, to be resistant to pharmacological inhibitors.

2019-06-05 | GSE125086 | GEO

Comprehensive profiling of translation initiation in influenza-virus infected cells

Project description:Cellular stress is often accompanied by non-canonical initiation of translation at alternate start codons in mammalian cells. Here we systematically investigate the extent and impact of alternate translation initiation in the context of influenza virus infection. We use ribosome profiling with the initiation inhibitor lactidomycin to experimentally delineate translation initiation sites in a human lung epithelial cell line infected with influenza virus.

2018-05-20 | GSE114636 | GEO

Discovery of non-canonical translation initiation sites through mass spectrometric analysis of protein N-termini

Project description:Translation initiation generally occurs at AUG codons in eukaryotes although it has been shown that non-AUG or non-canonical translation initiation can also occur. However, the evidence for non-canonical translation initiation sites (TISs) is largely indirect and based on ribosome profiling studies. Here, using a strategy specifically designed to enrich N-termini of proteins, we demonstrate that many human proteins are translated at non-canonical TISs. The large majority of TISs that mapped to 5’ untranslated regions were non-canonical and led to N-terminal extension of annotated proteins or translation of upstream small open reading frames (uORF). There has been little controversy on whether the corresponding amino acid to the start codon is incorporated at TIS or methionine is still incorporated. Notably, methionine was incorporated at almost all non-canonical TISs identified in this study. Comparison of the TISs determined through mass spectrometry with ribosome profiling data revealed that about two-thirds of the novel annotations were indeed supported by ribosome profiling data. The sequence orthology analysis and relative translation frequency analysis of non-canonical TISs over canonical ones suggests that those non-canonical TISs are not leaky but they can have certain biological functions. Overall, this study provides evidence of protein translation initiation at non-canonical TISs and indicates that further studies are required for elucidation of functional implications of such non-canonical translation initiation.

2017-11-23 | PXD006633 | Pride

eIF1A residues implicated in cancer stabilize translation preinitiation complexes and favor suboptimal initiation sites in yeast

Project description:The translation pre-initiation complex (PIC) scans the mRNA for an AUG codon in favorable context, and AUG recognition stabilizes a closed PIC conformation. The unstructured N-terminal tail (NTT) of yeast eIF1A deploys five basic residues to contact tRNAi, mRNA, or 18S rRNA exclusively in the closed state. Interestingly, EIF1AX mutations altering the human eIF1A NTT are associated with uveal melanoma (UM). We found that substituting all five basic residues, and seven UM-associated substitutions, in yeast eIF1A suppresses initiation at near-cognate UUG codons and AUGs in poor context. Ribosome profiling of NTT substitution R13P reveals heightened discrimination against unfavorable AUG context genome-wide. Both R13P and K16D substitutions destabilize the closed complex at UUG codons in reconstituted PICs. Thus, electrostatic interactions involving the eIF1A NTT stabilize the closed conformation and promote utilization of suboptimal start codons. We predict UM-associated mutations alter human gene expression by increasing discrimination against poor initiation sites.

2017-12-21 | GSE108334 | GEO

Bi-directional ribosome scanning controls the stringency of start codon selection

Project description:The fidelity of start codon recognition by ribosomes is paramount during protein synthesis. The textbook knowledge of eukaryotic translation initiation depicts 5’→3’ unidirectional migration of the pre-initiation complex (PIC) along the 5’UTR. In probing translation initiation from ultra-short 5’UTR, we report that an AUG triplet near the 5’ end can be selected via PIC backsliding. The bi-directional ribosome scanning is supported by competitive selection of closely spaced AUG codons and recognition of two initiation sites flanking an internal ribosome entry site. Transcriptome-wide PIC profiling reveals footprints with an oscillation pattern near the 5’ end and start codons. Depleting the RNA helicase eIF4A leads to reduced PIC oscillations and impaired selection of 5’ end start codons. Enhancing the ATPase activity of eIF4A promotes nonlinear PIC scanning and stimulates upstream translation initiation. The helicase-mediated PIC conformational switch may provide an operational mechanism that unifies ribosome recruitment, scanning, and start codon selection.

2021-11-24 | GSE176058 | GEO

Direct epitranscriptomic regulation of mammalian translation initiation through N4-acetylcytidine

Project description:mRNA function is influenced by modifications that modulate canonical nucleobase behavior. We show that a single modification mediates distinct impacts on mRNA translation in a position-dependent manner. While cytidine acetylation (ac4C) within protein-coding sequences stimulates translation, ac4C within 5’UTRs impacts protein synthesis at the level of initiation. 5’UTR acetylation promotes initiation at upstream sequences, competitively inhibiting annotated start codons. Acetylation further directly impedes initiation at optimal AUG contexts: ac4C within AUG-flanking Kozak sequences reduced initiation in base-resolved transcriptome-wide HeLa results, and in vitro utilizing substrates with site-specific ac4C incorporation. Cryo-EM of mammalian 80S initiation complexes revealed ac4C in the -1-position adjacent to an AUG start codon disrupts an interaction between C and hypermodified t6A at nucleotide 37 of the initiator tRNA. These findings demonstrate the impact of RNA modifications on nucleobase function at a molecular level and introduce mRNA acetylation as a factor regulating translation in a location-specific manner.

2022-06-08 | GSE162043 | GEO

Genome-wide search for novel human uORFs and N-terminal protein extensions using ribosomal footprinting

Project description:So far, the annotation of translation initiation sites (TISs) has been based mostly upon bioinformatics rather than experimental evidence. We adapted ribosomal footprinting to puromycin-treated cells to generate a transcriptome-wide map of TISs in a human monocytic cell line. A neural network was trained on the ribosomal footprints at previously annotated AUG translation initiation codons (TICs), and used for the ab initio prediction of TISs in 5062 transcripts with sufficient sequence coverage. Functional interpretation suggested 2994 novel upstream open reading frames (uORFs) in the 5´ UTR (924 AUG, 2070 near-cognate codons), 1406 uORFs overlapping with the coding sequence (116 AUG, 1290 near-cognate) and 546 N-terminal protein extensions (6 AUG, 540 near-cognate). The TIS detection method was validated on the basis of previously published alternative TISs and uORFs. On average, TICs in newly annotated TISs were significantly more conserved among primates than control codons, both for AUGs (p<10-10) and near-cognate codons (p=3.8×10-3). The derived transcriptome-wide map of novel candidate TISs will help to explain how human proteome diversity is influenced by alternative translation initiation and regulation. Examination of translational initiation in human cell lines using ribosomal footprinting

2012-08-08 | E-GEOD-39561 | biostudies-arrayexpress

Evolutionarily Conserved Inhibitory uORFs Sensitize Hox mRNA Translation to Start Codon Selection Stringency

Project description:Translation start site selection in eukaryotes is influenced by context nucleotides flanking the AUG codon and by levels of the eukaryotic translation initiation factors eIF1 and eIF5. In a search of human genes, we identified 5 Hox gene paralogs initiated by AUG codons in conserved suboptimal context as well as 13 Hox genes that contain evolutionarily conserved upstream open reading frames (uORFs) that initiate at AUG codons in poor sequence context. We analyzed published CAGE-seq data and generated CAGE-seq data from mRNAs from mouse somites. These data demonstrate that the 5’ leaders of Hox mRNAs of interest contain conserved uORFs, are much shorter than reported, and lack previously proposed IRES elements. We show that the conserved uORFs inhibit Hox reporter expression and that altering the stringency of start codon selection by overexpressing eIF1 or eIF5 modulates the expression of Hox reporters. We also show that modifying ribosome homeostasis by depleting a large ribosomal subunit protein or treating cells with sublethal concentrations of puromycin leads to lower stringency of start codon selection. Thus, altering global translation can confer gene-specific effects through altered start codon selection stringency.

2022-02-21 | GSE184515 | GEO

Genome-wide search for novel human uORFs and N-terminal protein extensions using ribosomal footprinting

2012-08-08 | GSE39561 | GEO

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data