Deinococcus radiodurans
Ontology highlight
ABSTRACT:
PROVIDER: PRJNA386750 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| SRR5571032_1.fastq.gz | Fastqsanger.gz | |||
| SRR5571032_2.fastq.gz | Fastqsanger.gz | |||
| SRR5580756_1.fastq.gz | Fastqsanger.gz | |||
| SRR5580756_2.fastq.gz | Fastqsanger.gz |
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Project description:The nascent polypeptide-associated complex (NAC) is crucial for protein biogenesis, coordinating enzymatic modifications and membrane targeting of nascent chains at the ribosomal tunnel exit. However, its role in co-translational folding remains unclear. Here, we report the genome-wide profiling of NAC interactions with nascent chains in human cells, demonstrating that it correlates with emerging segments of folded domains of cytonuclear proteins. Single-molecule and structural analyses revealed that NAC’s b-barrel domain dynamically interacts with the ribosome and emerging chains at the tunnel exit, presumably facilitating initial compaction and early folding, and that NAC binding promotes native folding of proteins. Additionally, we uncovered compartment-specific nascent chain interactions of NAC, supporting it’s role in targeting proteins to the endoplasmic reticulum and in mitochondrial membrane protein biogenesis. Together, these findings establish NAC as a bona fide co-translational chaperone that facilitates early protein folding at the ribosomal tunnel exit, expanding its functional repertoire in protein biogenesis.
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Project description:The guided entry of tail-anchored proteins (GET) pathway assists in the proper delivery of tail-anchored (TA) proteins to the ER. Here we uncover how the yeast GET pathway components Get4/5 mediate capture of TA proteins by Sgt2, which interacts with TA sequences and hands them over to the targeting component Get3. Get4/5 binds directly and with high affinity to ribosomes, positions Sgt2 close to the ribosomal tunnel exit, and facilitates the capture of TA proteins by Sgt2. The contact sites of Get4/5 on the ribosome overlap with those of SRP, the factor mediating cotranslational ER-targeting of proteins containing internal TM domains. Exposure of nascent, internal TM domains at the tunnel exit induces high-affinity ribosome-binding of SRP, which in turn prevents ribosome-binding of Get4/5. In this way, the position of TM domains within nascent ER-targeted proteins mediates partitioning into either the GET or SRP pathway directly at the ribosomal tunnel exit.
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Project description:Understanding the conformational sampling of translation-arrested ribosome nascent chain complexes is key to understand co-translational folding. Up to now, coupling of cysteine oxidation, disulfide bond formation and structure formation in nascent chains has remained elusive. Here, we investigate the eye-lens protein γB-crystallin in the ribosomal exit tunnel. Using mass spectrometry, theoretical simulations, dynamic nuclear polarization-enhanced solid-state nuclear magnetic resonance and cryo-electron microscopy, we show that thiol groups of cysteine residues undergo S-glutathionylation and S-nitrosylation and form non-native disulfide bonds. Thus, covalent modification chemistry occurs already prior to nascent chain release as the ribosome exit tunnel provides sufficient space even for disulfide bond formation which can guide protein folding.
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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 cellular environment is critical for efficient protein maturation, but how proteins fold during biogenesis remains poorly understood. We used hydrogen/deuterium exchange (HDX) mass spectrometry (MS) to define, at peptide resolution, the cotranslational chaperone-assisted folding pathway of Escherichia coli dihydrofolate reductase. On the ribosome, the nascent polypeptide folds via structured intermediates not populated during refolding from denaturant. Association with the ribosome allows these intermediates to form, as otherwise destabilizing C-terminal sequences remain confined in the ribosome exit tunnel. We find that partially-folded nascent chains recruit the chaperone Trigger factor, which uses a large composite hydrophobic/hydrophilic interface to engage folding intermediates without disrupting their structure. In addition, we comprehensively mapped dynamic interactions between the nascent chain and ribosomal proteins, tracing the path of the emerging polypeptide during synthesis. Our work provides a high-resolution description of de novo protein folding dynamics, thereby revealing new mechanisms by which cellular factors shape the conformational search for the native state.
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Project description:NAC promotes co-translational protein folding at the ribosomal tunnel exit
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Project description:Cotranslational protein folding depends on general chaperones that engage highly diverse nascent chains at the ribosomes. Here we find that the universal cotranslational machinery adapts to accommodate the challenging biogenesis of abundantly expressed eukaryotic translation elongation factor 1A (eEF1A). During eEF1A synthesis, chaperone Chp1 is recruited to the ribosome with the help of the nascent polypeptide-associated complex (NAC), where it safeguards eEF1A biogenesis. Aberrant eEF1A production triggers instant proteolysis, widespread protein aggregation, activation of Hsf1 stress transcription and compromises cellular fitness. The expression of pathogenic eEF1A2 variants linked to epileptic-dyskinetic encephalopathy is protected by Chp1. Thus, eEF1A is a difficult to fold protein that necessitates dedicated folding factor Chp1 at the ribosomal tunnel exit to protect the eukaryotic cell from proteostasis collapse.
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Project description:The nascent polypeptide-associated complex (NAC) is a conserved ribosome-bound factor with essential yet incompletely understood roles in protein biogenesis1. Here, we show that NAC is a multifaceted regulator that coordinates translation elongation, cotranslational folding, and organelle targeting through distinct interactions with nascent polypeptides both inside and outside the ribosome exit tunnel. Using NAC-selective ribosome profiling in C. elegans, we identify thousands of sequence-specific NAC binding events across the nascent proteome, revealing broad cotranslational engagement with hydrophobic and helical motifs in cytosolic, nuclear, ER, and mitochondrial proteins. Unexpectedly, we discover an intra-tunnel sensing mode, where NAC engages ribosomes with extremely short nascent polypeptides inside the exit tunnel in a sequence-specific manner. Moreover, initial NAC interactions induce an early elongation slowdown that tunes ribosome flux and prevent ribosome collisions, linking NAC’s chaperone activity to kinetic control of translation. We propose NAC action protects aggregation-prone intermediates by shielding amphipathic helices, thus promoting cytonuclear folding. NAC also supports mitochondrial membrane protein biogenesis and ER targeting by early recognition of signal sequences and transmembrane domain. Our findings establish NAC as an early-acting, multifaceted orchestrator of cotranslational proteostasis, with distinct mechanisms of action on nascent chains depending on their sequence features and subcellular destinations.
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Project description:The nascent polypeptide-associated complex (NAC) is a conserved ribosome-bound factor with essential yet incompletely understood roles in protein biogenesis1. Here, we show that NAC is a multifaceted regulator that coordinates translation elongation, cotranslational folding, and organelle targeting through distinct interactions with nascent polypeptides both inside and outside the ribosome exit tunnel. Using NAC-selective ribosome profiling in C. elegans, we identify thousands of sequence-specific NAC binding events across the nascent proteome, revealing broad cotranslational engagement with hydrophobic and helical motifs in cytosolic, nuclear, ER, and mitochondrial proteins. Unexpectedly, we discover an intra-tunnel sensing mode, where NAC engages ribosomes with extremely short nascent polypeptides inside the exit tunnel in a sequence-specific manner. Moreover, initial NAC interactions induce an early elongation slowdown that tunes ribosome flux and prevent ribosome collisions, linking NAC’s chaperone activity to kinetic control of translation. We propose NAC action protects aggregation-prone intermediates by shielding amphipathic helices, thus promoting cytonuclear folding. NAC also supports mitochondrial membrane protein biogenesis and ER targeting by early recognition of signal sequences and transmembrane domain. Our findings establish NAC as an early-acting, multifaceted orchestrator of cotranslational proteostasis, with distinct mechanisms of action on nascent chains depending on their sequence features and subcellular destinations.
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