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Ribosome profiling study of rli1 depeletion strain

ABSTRACT: ABCE1/Rli1 functions as a ribosome recycling factor in vitro, but has not been shown to be crucial for recycling in vivo. We use ribosome profiling and biochemistry to define the role of Rli1 in living yeast. When Rli1 levels were diminished, 80S ribosomes accumulated at stop codons and, surprisingly, in the adjoining 3'UTRs of most genes. While ribosomes did not show preference for any reading frame in the 3'UTR, their enrichment at stop codons and His codons after histidine starvation is consistent with aberrant 3'UTR translation. Predicted 3'UTR translation products were detected by Western analysis and mass spectrometry, and their small sizes indicate a reinitiation mechanism. Eliminating ribosome-rescue factor Dom34 dramatically increases 3'UTR ribosome occupancy in Rli1 depleted cells, indicating that Dom34 clears the bulk of unrecycled ribosomes. Thus, Rli1 is crucial for ribosome recycling in vivo and for overall gene expression as it controls ribosome homeostasis and 3'UTR translation.

ORGANISM(S): Saccharomyces cerevisiae

PROVIDER: GSE69414 | GEO | 2015/06/02

SECONDARY ACCESSION(S): PRJNA285458

REPOSITORIES: GEO

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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.

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Ribosome profiling study of rli1 depeletion strain

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