Ageing-dependent ribosome pausing and nascent polypeptide aggregation
Ontology highlight
ABSTRACT:
PROVIDER: PRJNA640641 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| SRR12055100.fastq.gz | Fastqsanger.gz | |||
| SRR12055101.fastq.gz | Fastqsanger.gz | |||
| SRR12055102.fastq.gz | Fastqsanger.gz | |||
| SRR12055103.fastq.gz | Fastqsanger.gz | |||
| SRR12055104.fastq.gz | Fastqsanger.gz |
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Project description:Increased protein misfolding and aggregation are key hallmarks of ageing and many age-related diseases. As generating and maintaining a functional proteome (proteostasis) is crucial to every cellular process, this age-related decline in proteostasis is suggested to play a primary role in the breakdown of diverse cellular subsystems during ageing. Indeed, augmented proteostasis pathways are associated with extended lifespan across different species. With the ribosome as the earliest proteostasis checkpoint, decreased protein synthesis is also a conserved mechanism that extends lifespan. Yet, it remains unclear whether ageing impacts translation after initiation. Here, we use worms and yeast to investigate how ageing influences translation elongation. We show an age-dependent increase in ribosome pausing at diverse positions in coding sequences. This pausing is conserved in both worms and yeast, particularly at Arg and polybasic regions. We further show that such pausing is associated with the age-dependent aggregation of truncated nascent proteins involved in proteostasis pathways, notably aminoacyl tRNA synthetases. Moreover, we find that impairment in clearing truncated nascent proteins is associated with decreased lifespan. These data establish elongation kinetics and co-translational quality control as critical contributors of the age-related proteostasis collapse, which may precipitate the systemic decline observed during ageing.
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Project description:Continuous translation elongation, irrespective of amino acid sequences, is a prerequisite for living organisms to produce their proteomes. However, the risk of elongation abortion is concealed within nascent polypeptide products. For example, negatively charged sequences with occasional intermittent prolines, termed intrinsic ribosome destabilization (IRD) sequences, destabilizes the translating ribosomal complex. Thus, some nascent chain sequences lead to premature translation cessation. Here, we show that most potential IRD sequences in the middle of open reading frames remain cryptic by two mechanisms: the nascent polypeptide itself that spans the exit tunnel and its bulky amino acid residues that occupy the tunnel entrance region. Thus, nascent polypeptide products have a built-in ability to ensure elongation continuity by serving as a bridge and thus by protecting the large and small ribosomal subunits from dissociation.
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Project description:The breach of proteostasis, leading to the accumulation of protein aggregates, is a hallmark of ageing and age-associated disorders, up to now well-established in neurodegeneration. Few studies have addressed the issue of dysfunctional cell response to protein deposition also for the cardiovascular system. However, the molecular basis of proteostasis decline in vascular cells, as well as its relation to ageing, are not understood. Recent studies have indicated the associations of Nrf2 transcription factor, the critical modulator of cellular stress-response, with ageing and premature senescence. In this report, we outline the significance of protein aggregation in physiological and premature ageing of murine and human endothelial cells (ECs). Our study shows that aged donor-derived and prematurely senescent Nrf2-deficient primary human ECs, but not those overexpressing dominant-negative Nrf2, exhibit increased accumulation of protein aggregates. Such phenotype is also found in the aortas of aged mice and young Nrf2 tKO mice. Ageing-related loss of proteostasis in ECs depends on Keap1, well-known repressor of Nrf2, recently perceived as a key independent regulator of EC function. Ageing-induced deposition of protein aggregates in ECs is associated with impaired autophagy and can be counteracted by Keap1 depletion or rapamycin treatment. Our results show that Keap1:Nrf2 protein balance predominates Nrf2 transcription-dependent mechanisms in governing proteostasis and ageing in ECs.
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Project description:Nascent polypeptide within the exit tunnel stabilizes the ribosome to counteract risky translation
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Project description:Translation initiation is considered overall rate-limiting for protein biosynthesis, whereas the impact of non-uniform ribosomal elongation rates is largely unknown. Using a modified ribosome profiling protocol based on footprints from two closely packed ribosomes (disomes), we have mapped ribosomal collisions transcriptome-wide in mouse liver. We uncover that the stacking of an elongating onto a paused ribosome occurs frequently and scales with translation rate, trapping ~10% of translating ribosomes in the disome state. A distinct class of pause sites, independent of translation rate, is indicative of deterministic pausing signals. We find pause sites associated with specific codons, amino acids, and peptide motifs, and with structural features of the nascent polypeptide, suggestive of programmed pausing as a widespread mechanism associated with protein folding. Evolutionary conservation at disome sites and experiments indicate functional relevance of translational pausing. Collectively, our disome profiling approach allows novel and unexpected insights into gene regulation occurring at the step of translation elongation.
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Project description:We report a new platform for the rapid phenotypic selection of protein aggregation inhibitors from genetically encoded cyclic peptide libraries in E. coli based on phage-assisted continuous evolution (PACE). Here, we developed a new PACE-compatible selection for protein aggregation inhibition and employed it to identify cyclic peptides that suppress amyloid-β42 (Aβ42) and human islet amyloid polypeptide (hIAPP) aggregation. Additionally, we integrated a negative selection that removes false positives and off-target hits, significantly improving cyclic peptide selectivity. We show that selected inhibitors are active when chemically re-synthesized in in vitro assays. Our platform provides a powerful new approach for the rapid discovery of cyclic peptide inhibitors of protein aggregation and may serve as the basis for the future evolution of cyclic peptides with a broad spectrum of inhibitory activities. Data deposited here are HTS data critical to the conclusions of this study.
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Project description:Embryonic stem (ES) cells and embryos reversibly pause via chemical mTOR inhibition. In this study, we investigate the tissue-specific response to mTORi-induced pausing in ES and trophoblast stem (TS) cells. To resolve the sequential rewiring of the proteome, we conducted a time-series proteomics experiment at 1, 3, 6, 12, 24, and 48 hours upon induction of pausing, and at 1, 3, 6, 12, 24, and 48 hours upon release of pausing in ES and TS cells. We find that ES, but not TS cells pause reversibly. To optimise developmental pausing conditions, we reasoned that by understanding the difference in pausing response of ES and TS cells, we could identify which pathways are essential for pausing. We found that KEGG pathways related to amino acid degradation, fatty acid degradation, and DNA repair are upregulated in ES cells, but downregulated in TS cells during entry into pausing. Moreover, by targeted metabolomics, we found a depletion of short chain carnitines in the paused ES cells. To extend the length of developmental pausing, we supplemented paused embryos with L-carnitine. The L-carnitine supplementation facilitates lipid usage and prolongs the pausing length by 19 days through the establishment of a more dormant state.
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