Dataset Information

Ribosome profiling of WT strain in Neurospora crass

ABSTRACT: Codon usage bias, which refers to uneven use of synonymous codons, was shown to associate with mRNA stability from yeast to human. However, the underlying molecular basis is largely unknown. With bioinformatic analyses we unexpectedly found that codon usage bias is inversely correlated to density of out-of-frame stop codons (hidden stop codon or HSC). To understand the physiological function of HSCs, we use the frequency gene of Neurospora crassa to examine the role of HSCs in circadian rhythm. We show that deleting HSCs in the upstream of frequency (frq) open reading frame without altering FRQ sequence resulted in loss of circadian rhythm. Further analyses revealed that HSC deletion of frq resulted in elevated stability of frq mRNA, which consequently causes higher FRQ protein level. Combined various methods, we showed that rare codons in the upstream frq region generates significant amount of aberrant translation at +1 frame, possibly via ribosomal frameshifting. Consistently, at genome wide we showed that both in N. crassa and S. cerevisiae, the codon usage bias combined with numbers of HSC are inversely correlated to mRNA stability. Together, these data indicate that HSCs might act as an intrinsic mechanism to terminate aberrant ribosomal frameshifting events triggered by non-optimal codons, thus fine-tune mRNA stability.

ORGANISM(S): Neurospora crassa

PROVIDER: GSE245041 | GEO | 2023/12/31

REPOSITORIES: GEO

ACCESS DATA

Similar Datasets

Project description:Many tumors escape by activating multiple cellular pathways that induce immunosuppression. One pivotal immune-suppressive mechanism is the production of tryptophan metabolites along the kynurenine pathway by IFNγ-induced IDO1 enzyme production 4-8. Phase III clinical trials using chemical inhibition of IDO1 in combination with PD1 pathway blockade, however, failed to improve melanoma treatment 9-12. This points at an incomplete understanding of the role of IDO1 and the consequent tryptophan degradation on mRNA translation and cancer progression. Here, we investigated the effects of prolonged IFNγ treatment on mRNA translation in melanoma cells by ribosome profiling. Surprisingly, we observed a massive accumulation of ribosomes ~20 amino acids downstream of tryptophan codons (termed here as W-Bumps) along with their expected stalling at the tryptophan codon itself. This indicated ribosomal bypass of the tryptophan codons in the absence of tryptophan. Detailed examination of W-Bumps position and its corresponding peptide sequences pinpointed towards ribosomal frameshifting events and their effects in the ribosome exit tunnel. In particular, W-Bumps strength was associated with the disorderedness level of potential out-of-frame peptides predicted downstream of tryptophan codons. Indeed, reporter assays demonstrated the induction of ribosomal frameshifting, and the generation of trans-frame proteins and their presentation at the cell surface after IFNγ treatment. Proteomics and immunopeptidomics analyses verified the production of IFNγ-induced trans-frame and out-of-frame aberrant peptides and their presentation on HLA class I molecules. Priming of naïve T cells from healthy donors with aberrant peptides resulted in identification of reactive, peptide-specific T cells. Altogether, our results suggest that IFNγ-induced IDO1-mediated tryptophan depletion plays a role in the immune recognition of melanoma cells by contributing to the diversity of the peptidome landscape, and by inducing the presentation of aberrant peptides.

Project description:Terminating protein translation accurately and efficiently is critical for both protein fidelity and ribosome recycling for continued translation. The three bacterial release factors (RFs) play key roles: RF1 and 2 recognize stop codons and terminate translation; and RF3 promotes disassociation of bound release factors. Probing release factors mutations with reporter constructs containing programmed frameshifting sequences or premature stop codons had revealed a propensity for readthrough or frameshifting at these specific sites, but their effects on translation genome-wide have not been examined. We performed ribosome profiling on a set of isogenic strains with well-characterized release factor mutations to determine how they alter translation globally. Consistent with their known defects, strains with increasingly severe release factor defects exhibit increasingly severe accumulation of ribosomes over stop codons, indicative of an increased duration of the termination/release phase of translation. Release factor mutant strains also exhibit increased occupancy in the region following the stop codon at a significant number of genes. Our global analysis revealed that, as expected, translation termination is generally efficient and accurate, but that at a significant number of genes (≥ 50) the ribosome signature after the stop codon is suggestive of translation past the stop codon. Even native E. coli K-12 exhibits the ribosome signature suggestive of protein extension, especially at UGA codons, which rely exclusively on the reduced function RF2 allele of the K-12 strain for termination. Deletion of RF3 increases the severity of the defect. We unambiguously demonstrate readthrough and frameshifting protein extensions and their further accumulation in mutant strains for a few select cases. In addition to enhancing recoding, ribosome accumulation over stop codons disrupts attenuation control of biosynthetic operons, and may alter expression of some overlapping genes. Together, these functional alterations may either augment the protein repertoire or produce deleterious proteins.

Dataset Information

Ribosome profiling of WT strain in Neurospora crass

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure