The ASC-1 complex promotes translation initiation of the scanning ribosomes
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ABSTRACT:
PROVIDER: PRJNA774189 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| SRR16561700.fastq.gz | Fastqsanger.gz | |||
| SRR16561701.fastq.gz | Fastqsanger.gz | |||
| SRR16561702.fastq.gz | Fastqsanger.gz | |||
| SRR16561703.fastq.gz | Fastqsanger.gz | |||
| SRR16561704.fastq.gz | Fastqsanger.gz |
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Project description:Translation is initiated by binding of the eIF4F complex to the 5' cap of the mRNA, which is followed by scanning of the initiation codon by scanning ribosomes. Here we demonstrate that the ASC-1 complex (ASCC), which was previously shown to promote the dissociation of colliding 80S ribosomes, associates with the scanning ribosomes to regulate translation initiation. Sel-TCP-seq analysis revealed that ASCC3, a subunit of ASCC with a helicase domain, localizes predominantly to the 5' untranslated region of mRNAs. Knockdown of ASCC3 resulted in reduced translation efficiency associated with reduced 43S preinitiation complex (PIC) loading and a reduced speed of scanning ribosomes. In addition, depletion of the ubiquitin ligase ZNF598, a sensor of collided 80S ribosomes, also reduces the PIC loading and speed of scanning ribosomes. Our results have thus revealed that ASCC is required not only for dissociation of colliding 80S ribosomes, but also for efficient translation initiation by scanning ribosomes.
2023-03-31 | GSE186502 | GEO
Project description:Translation regulation occurs largely during initiation. Currently, translation initiation can be studied in vitro, but these systems lack features present in vivo and on endogenous mRNAs. Here we develop selective 40S footprinting for visualizing initiating 40S ribosomes on endogenous mRNAs in vivo. It pinpoints where on an mRNA initiation factors join the ribosome to act, and where they leave. We discover that in human cells most scanning ribosomes remain attached to the 5’ cap. Consequently, only one ribosome scans a 5’UTR at a time, and 5’UTR length affects translation efficiency. We discover that eIF3B, eIF4G1 and eIF4E remain on translating 80S ribosomes with a decay half-length of ~12 codons. Hence ribosomes retain these initiation factors while translating short upstream Open Reading Frames (uORFs), providing an explanation for how ribosomes can re-initiate translation after uORFs in humans. This method will be of use for studying translation initiation mechanisms in vivo.
2020-06-25 | GSE139391 | GEO
Project description:Most animal mRNAs contain upstream Open Reading Frames (uORFs). These uORFs represent an impediment to translation of the main ORF since ribosomes usually bind the mRNA cap at the 5’ end and then scan for ORFs in a 5’-to-3’ fashion. One way for ribosomes to bypass uORFs is via leaky scanning, whereby the ribosome disregards the uORF start codon. Hence leaky scanning is an important post-transcriptional mechanism affecting gene expression. Few molecular factors regulating or facilitating this process are known. Here we identify the PRRC2 proteins PRRC2A, PRRC2B and PRRC2C as translation initiation factors. We find that they bind other eukaryotic translation initiation factors and preinitiation complexes and are enriched on ribosomes translating mRNAs with uORFs. We find that PRRC2 proteins promote translation of mRNAs containing uORFs by facilitating leaky scanning past uORFs. Since PRRC2 proteins have been associated with cancer, this provides a mechanistic starting point for understanding their physiological and pathophysiological roles.
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Project description:Relaxed initiation pausing of ribosomes drives oncogenic translation
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Project description:Using quantitative profiling of initiating ribosomes, we found that ribosomal pausing at the start codon serves as a “brake” to restrain the translational output. In response to oncogenic RAS signaling, the initiation pausing relaxes and contributes to the increased translational flux. Intriguingly, mRNA m6A modification in the vicinity of start codons influences the behavior of initiating ribosomes. Under oncogenic RAS signaling, the reduced mRNA methylation leads to relaxed initiation pausing, thereby promoting malignant transformation and tumor growth. Restored initiation pausing by inhibiting m6A demethylases suppresses RAS-mediated oncogenic translation and subsequent tumorigenesis. Our findings unveil a new paradigm of translational control that is co-opted by RAS mutant cancer cells to drive malignant phenotypes.
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Project description:Translation initiates when the eIF4F complex binds the 5' mRNA cap, followed by 5' untranslated region scanning for the start codon by scanning ribosomes. Here we demonstrate that the ASC-1 complex (ASCC), which was previously shown to promote the dissociation of colliding 80S ribosomes, associates with scanning ribosomes to regulate translation initiation. Selective translation complex profiling (TCP-seq) analysis revealed that ASCC3, a helicase domain-containing subunit of ASCC, localizes predominantly to the 5' untranslated region of mRNAs. Ribo-seq, TCP-seq, and luciferase reporter analyses showed that ASCC3 knockdown impairs 43S preinitiation complex loading and scanning dynamics, thereby reducing translation efficiency. Whereas eIF4A, an RNA helicase in the eIF4F complex, is important for global translation, ASCC was found to regulate the scanning process for a specific subset of transcripts. Our results have thus revealed that ASCC is required not only for dissociation of colliding 80S ribosomes, but also for efficient translation initiation by scanning ribosomes at a subset of transcripts.
| S-SCDT-10_15252-EMBJ_2022112869 | biostudies-other
Project description:Cellular responses to environmental stress are frequently mediated by RNA-binding proteins (RBPs). Here, we examined global RBP dynamics in Saccharomyces cerevisiae in response to glucose starvation and heat shock. Each stress induced rapid remodeling of the RNA-protein interactome, without corresponding changes in RBP abundance. Consistent with general translation shutdown, ribosomal proteins contacting the mRNA showed decreased RNA-association. Among translation components, RNA-association was most reduced for initiation factors involved in 40S scanning (eIF4A, eIF4B, and Ded1), indicating a common mechanism of translational repression. In unstressed cells, eIF4A, eIF4B, and Ded1 primarily targeted the 5′-ends of mRNAs. Following glucose withdrawal, 5’-binding was abolished within 30sec, explaining the rapid translation shutdown, but mRNAs remained stable. Heat shock induced progressive loss of 5’ RNA-binding by initiation factors over ~16min. Translation shutoff provoked selective 5′-degradation of mRNAs encoding translation-related factors, mediated by Xrn1. These results reveal mechanisms underlying translational control of gene expression during stress.
2020-06-08 | GSE148166 | GEO
Project description:eIF3 is a multi-subunit complex thought to execute numerous functions in canonical translation initiation, including mRNA recruitment to the 40S ribosome, scanning for the start codon, and inhibition of 60S subunit joining 1–3. eIF3 was also found to interact with 40S and 60S ribosomal proteins and translation elongation factors 4, but a direct involvement in translation elongation has never been demonstrated. Using selective ribosome profiling, we made the unexpected observation that eIF3 remains bound to post-initiation 80S ribosomes, followed by release after translation of ~50 codons. Furthermore, eIF3 deficiency reduces early ribosomal elongation speed, particularly on mRNAs encoding proteins associated with membrane-associated functions, resulting in defective synthesis of their encoded proteins and abnormal mitochondrial and lysosomal physiology. Accordingly, heterozygous eIF3e+/- knockout mice accumulate giant mitochondria in skeletal muscle and show a progressive decline in muscle strength with age. Hence, in addition to its canonical role in translation initiation, eIF3 interacts with 80S ribosomes to enhance, at the level of early elongation, the synthesis of proteins with membrane-associated functions, an activity that is critical for normal muscle health.
2020-06-15 | GSE149697 | GEO
Project description:Stress-induced translation inhibition through release of 40S scanning initiation factors
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Project description:Cellular responses to environmental stress are frequently mediated by RNA-binding proteins (RBPs). Here, we examined global RBP dynamics in Saccharomyces cerevisiae in response to glucose starvation and heat shock. Each stress induced rapid remodeling of the protein:RNA interactome, without corresponding changes in RBP abundance. Consistent with general translation shutdown, ribosomal proteins contacting the mRNA showed decreased RNA-association. Among translation components, RNA-association was most reduced for initiation factors involved in 40S scanning (eIF4A, eIF4B, and Ded1), indicating a common mechanism of translational repression. In unstressed cells, eIF4A, eIF4B, and Ded1 primarily targeted the 5′-ends of mRNAs. Following glucose withdrawal, mRNAs remained stable, but 5’-binding was abolished within 30sec, explaining the rapid translation shutdown. Heat shock induced progressive loss of 5’ RNA-binding by initiation factors over ~16min, and translation shutoff provoked 5′-degradation by Xrn1, selectively for mRNAs encoding translation-related factors. These results reveal mechanisms underlying translational control of gene expression during stress.
2020-10-13 | PXD019141 | Pride