scholarly journals A role for DIS3L2 over human nonsense-mediated mRNA decay targets

2019 ◽  
Author(s):  
Paulo J. da Costa ◽  
Juliane Menezes ◽  
Margarida Saramago ◽  
Juan F. García-Moreno ◽  
Hugo A. Santos ◽  
...  
Keyword(s):  
Translation Termination ◽  
Full Length ◽  
Nonsense Mediated Decay ◽  
Endonucleolytic Cleavage ◽  
Nonsense Mediated Mrna Decay ◽  
Translation Termination Codon ◽  
Life Analysis ◽  
Mrna Half Life ◽  
Premature Translation Termination Codon

ABSTRACTThe nonsense-mediated decay (NMD) pathway selectively degrades mRNAs carrying a premature translation-termination codon but also regulates the abundance of a large number of physiological mRNAs that encode full-length proteins. In human cells, NMD-targeted mRNAs are degraded by endonucleolytic cleavage and exonucleolytic degradation from both 5’ and 3’ ends. This is done by a process not yet completely understood that recruits decapping and 5’-to-3’ exonuclease activities, as well as deadenylating and 3’-to-5’ exonuclease exosome activities. In yeast, DIS3/Rrp44 protein is the catalytic subunit of the exosome, but in humans, there are three known paralogues of this enzyme: DIS3, DIS3L1, and DIS3L2. DIS3L1 and DIS3L2 exoribonucleases localize in the same compartment where NMD occurs, but little is known about their role in this process. In order to unveil the role of DIS3L2 in NMD, here we show that some NMD-targets accumulate in DIS3L2-depleted cells. mRNA half-life analysis further supports that these NMD-targets are in fact DIS3L2 substrates. Besides, we observed that DIS3L2 acts over full-length transcripts, through a process that also involves UPF1. Moreover, DIS3L2-mediated decay is dependent on the activity of the terminal uridylyl transferases Zcchc6/11 (TUT7/4). Together, our findings establish a role for DIS3L2 and uridylation in NMD.

scholarly journals An intron proximal to a PTC enhances NMD in Saccharomyces cerevisiae

2017 ◽  
Author(s):  
Jikai Wen ◽  
Muyang He ◽  
Marija Petric ◽  
Laetitia Marzi ◽  
Jianming Wang ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mammalian Cells ◽  
Mrna Decay ◽  
Translation Termination ◽  
Exon Junction Complex ◽  
Coding Region ◽  
Independent Mechanism ◽  
Nonsense Mediated Mrna Decay ◽  
Translation Termination Codon ◽  
Premature Translation Termination Codon

AbstractNonsense mediated mRNA decay (NMD) is regarded as the function of a specialized cytoplasmic translation-coupled mRNA decay pathway in eukaryotes, however, whether a premature translation termination codon (PTC) will lead to NMD often depends on splicing a downstream intron in the nucleus. Deposition of the exon junction complex (EJC) on mRNA is understood to mediate such splicing-dependent NMD in mammalian cells. The budding yeast, Saccharomyces cerevisiae, which has introns in only 5% of its genes, characteristically at the start of the coding region, and lacks proteins essential for EJC assembly, is not expected to undergo splicing-dependent NMD. However, we found that the presence of an intron near a PTC can also enhance NMD in this organism, regardless of whether it is downstream or upstream. These data provide evidence for a hitherto unsuspected EJC-independent mechanism linking translation and pre-mRNA in S. cerevisiae.

scholarly journals A UPF1 variant drives conditional remodeling of nonsense-mediated mRNA decay

2021 ◽  
Author(s):  
Sarah E. Fritz ◽  
Soumya Ranganathan ◽  
J. Robert Hogg
Keyword(s):  
Gene Expression ◽  
Mrna Decay ◽  
Gene Expression Regulation ◽  
Translation Termination ◽  
Translational Repression ◽  
The Core ◽  
Human Genes ◽  
Rna Quality Control ◽  
Nonsense Mediated Mrna Decay

AbstractThe nonsense-mediated mRNA decay (NMD) pathway monitors translation termination to degrade transcripts with premature stop codons and regulate thousands of human genes. Due to the major role of NMD in RNA quality control and gene expression regulation, it is important to understand how the pathway responds to changing cellular conditions. Here we show that an alternative mammalian-specific isoform of the core NMD factor UPF1, termed UPF1LL, enables condition-dependent remodeling of NMD specificity. UPF1LL associates more stably with potential NMD target mRNAs than the major UPF1SL isoform, expanding the scope of NMD to include many transcripts normally immune to the pathway. Unexpectedly, the enhanced persistence of UPF1LL on mRNAs supports induction of NMD in response to rare translation termination events. Thus, while canonical NMD is abolished by translational repression, UPF1LL activity is enhanced, providing a mechanism to rapidly rewire NMD specificity in response to cellular stress.

scholarly journals Intranuclear defect in beta-globin mRNA accumulation due to a premature translation termination codon

Blood ◽  
1984 ◽  
Vol 64 (1) ◽  
pp. 13-22 ◽  
Author(s):  
K Takeshita ◽  
BG Forget ◽  
A Scarpa ◽  
EJ Jr Benz
Keyword(s):  
Translation Termination ◽  
Beta Globin ◽  
Mrna Synthesis ◽  
Globin Mrna ◽  
Mrna Accumulation ◽  
S1 Nuclease ◽  
Translation Termination Codon ◽  
Premature Translation Termination ◽  
Premature Translation Termination Codon

Abstract We have analyzed a cloned beta O-thalassemia (beta O-thal) gene from a patient doubly heterozygous for hemoglobin Lepore and beta O- thalassemia. Studies of 3H-uridine incorporation into beta-globin mRNA in this patient's erythroblasts suggested an intranuclear defect in both beta and Lepore (delta beta) mRNA synthesis, as did S1 nuclease analysis of nuclear RNA. However, the nucleotide sequence of the beta O- thal gene revealed only a single base change in codon 39 (CAG----UAG), which created a premature translation termination codon. The 5′ flanking sequence, including transcription promotor boxes and the mRNA initiation (CAP) site, were normal. The unexpected effect of this mutation on intranuclear beta-mRNA synthesis in vivo was studied by insertion of the cloned gene into a plasmid expression vector and transfection into tissue culture (COS-1) cells. beta-Globin mRNA produced by the transfected cells was assessed by S1 nuclease analysis. The beta O-39 thalassemia gene generated five- to tenfold less beta- mRNA than a normal beta-gene in both nuclear and cytoplasmic RNA, simulating the results observed in vivo. Moreover, the small amount of beta O-39 mRNA produced was as stable as normal beta-mRNA during an actinomycin D chase, ruling out rapid cytoplasmic turnover as a cause of the reduced accumulation. Cotransfection of the beta O-39 thalassemia gene with a mutant tyrosine suppressor tRNA gene resulted in restoration of the beta O-39 mRNA accumulation to near-normal levels. On the basis of these results, we suggest that the low levels of beta-mRNA known to exist in the common form of beta O-thalassemia, beta O-39 thalassemia, result from a lesion in transcription, or early posttranscriptional processes; the defect appears to be corrected by restoration of proper translational potential to the mutant mRNA, at least in a gene transfer-expression system in tissue-culture cells.

scholarly journals CASC3 promotes transcriptome-wide activation of nonsense-mediated decay by the exon junction complex

2020 ◽  
Vol 48 (15) ◽  
pp. 8626-8644 ◽  
Author(s):  
Jennifer V Gerbracht ◽  
Volker Boehm ◽  
Thiago Britto-Borges ◽  
Sebastian Kallabis ◽  
Janica L Wiederstein ◽  
...  
Keyword(s):  
Exon Junction Complex ◽  
Core Component ◽  
Mrna Isoforms ◽  
Nonsense Mediated Decay ◽  
Exon Junction ◽  
Endonucleolytic Cleavage ◽  
Core Proteins ◽  
Messenger Ribonucleoprotein ◽  
Cytoplasmic Processes

Abstract The exon junction complex (EJC) is an essential constituent and regulator of spliced messenger ribonucleoprotein particles (mRNPs) in metazoans. As a core component of the EJC, CASC3 was described to be pivotal for EJC-dependent nuclear and cytoplasmic processes. However, recent evidence suggests that CASC3 functions differently from other EJC core proteins. Here, we have established human CASC3 knockout cell lines to elucidate the cellular role of CASC3. In the knockout cells, overall EJC composition and EJC-dependent splicing are unchanged. A transcriptome-wide analysis reveals that hundreds of mRNA isoforms targeted by nonsense-mediated decay (NMD) are upregulated. Mechanistically, recruiting CASC3 to reporter mRNAs by direct tethering or via binding to the EJC stimulates mRNA decay and endonucleolytic cleavage at the termination codon. Building on existing EJC-NMD models, we propose that CASC3 equips the EJC with the persisting ability to communicate with the NMD machinery in the cytoplasm. Collectively, our results characterize CASC3 as a peripheral EJC protein that tailors the transcriptome by promoting the degradation of EJC-dependent NMD substrates.

UPF1 involvement in nuclear functions

2012 ◽  
Vol 40 (4) ◽  
pp. 778-783 ◽  
Author(s):  
Wazeer Varsally ◽  
Saverio Brogna
Keyword(s):  
Dna Replication ◽  
Cell Cycle Progression ◽  
Translation Termination ◽  
Interaction Network ◽  
Rna Degradation ◽  
Telomere Maintenance ◽  
Human Proteins ◽  
Nonsense Mediated Mrna Decay ◽  
Rapid Destruction ◽  
Translation Termination Codon

UPF1 (up-frameshift 1) is a protein conserved in all eukaryotes that is necessary for NMD (nonsense-mediated mRNA decay). UPF1 mainly localizes to the cytoplasm and, via mechanisms that are linked to translation termination but not yet well understood, stimulates rapid destruction of mRNAs carrying a PTC (premature translation termination codon). However, some studies have indicated that in human cells UPF1 has additional roles, possibly unrelated to NMD, which are carried out in the nucleus. These might involve telomere maintenance, cell cycle progression and DNA replication. In the present paper, we review the available experimental evidence implicating UPF1 in nuclear functions. The unexpected view that emerges from this literature is that the nuclear functions primarily stem from UPF1 having an important role in DNA replication, rather than NMD affecting the expression of proteins involved in these processes. Our bioinformatics survey of the interaction network of UPF1 with other human proteins, however, highlights that UPF1 also interacts with proteins associated with nuclear RNA degradation and transcription termination; therefore suggesting involvement in processes that could also impinge on DNA replication indirectly.

scholarly journals Intranuclear defect in beta-globin mRNA accumulation due to a premature translation termination codon

Blood ◽  
1984 ◽  
Vol 64 (1) ◽  
pp. 13-22
Author(s):  
K Takeshita ◽  
BG Forget ◽  
A Scarpa ◽  
EJ Jr Benz
Keyword(s):  
Translation Termination ◽  
Beta Globin ◽  
Mrna Synthesis ◽  
Globin Mrna ◽  
Mrna Accumulation ◽  
S1 Nuclease ◽  
Translation Termination Codon ◽  
Premature Translation Termination ◽  
Premature Translation Termination Codon

We have analyzed a cloned beta O-thalassemia (beta O-thal) gene from a patient doubly heterozygous for hemoglobin Lepore and beta O- thalassemia. Studies of 3H-uridine incorporation into beta-globin mRNA in this patient's erythroblasts suggested an intranuclear defect in both beta and Lepore (delta beta) mRNA synthesis, as did S1 nuclease analysis of nuclear RNA. However, the nucleotide sequence of the beta O- thal gene revealed only a single base change in codon 39 (CAG----UAG), which created a premature translation termination codon. The 5′ flanking sequence, including transcription promotor boxes and the mRNA initiation (CAP) site, were normal. The unexpected effect of this mutation on intranuclear beta-mRNA synthesis in vivo was studied by insertion of the cloned gene into a plasmid expression vector and transfection into tissue culture (COS-1) cells. beta-Globin mRNA produced by the transfected cells was assessed by S1 nuclease analysis. The beta O-39 thalassemia gene generated five- to tenfold less beta- mRNA than a normal beta-gene in both nuclear and cytoplasmic RNA, simulating the results observed in vivo. Moreover, the small amount of beta O-39 mRNA produced was as stable as normal beta-mRNA during an actinomycin D chase, ruling out rapid cytoplasmic turnover as a cause of the reduced accumulation. Cotransfection of the beta O-39 thalassemia gene with a mutant tyrosine suppressor tRNA gene resulted in restoration of the beta O-39 mRNA accumulation to near-normal levels. On the basis of these results, we suggest that the low levels of beta-mRNA known to exist in the common form of beta O-thalassemia, beta O-39 thalassemia, result from a lesion in transcription, or early posttranscriptional processes; the defect appears to be corrected by restoration of proper translational potential to the mutant mRNA, at least in a gene transfer-expression system in tissue-culture cells.

scholarly journals CASC3 promotes transcriptome-wide activation of nonsense-mediated decay by the exon junction complex

2019 ◽  
Author(s):  
Jennifer V. Gerbracht ◽  
Volker Boehm ◽  
Thiago Britto-Borges ◽  
Sebastian Kallabis ◽  
Janica L. Wiederstein ◽  
...  
Keyword(s):  
Exon Junction Complex ◽  
Core Component ◽  
Mrna Isoforms ◽  
Nonsense Mediated Decay ◽  
Exon Junction ◽  
Endonucleolytic Cleavage ◽  
Core Proteins ◽  
Messenger Ribonucleoprotein ◽  
Cytoplasmic Processes

AbstractThe exon junction complex (EJC) is an essential constituent and regulator of spliced messenger ribonucleoprotein particles (mRNPs) in metazoans. As a core component of the EJC, CASC3 was described to be pivotal for EJC-dependent nuclear and cytoplasmic processes. However, recent evidence suggests that CASC3 functions differently from other EJC core proteins. Here, we have established human CASC3 knockout cell lines to elucidate the cellular role of CASC3. In the knockout cells, overall EJC composition and EJC-dependent splicing are unchanged. A transcriptome-wide analysis reveals that hundreds of mRNA isoforms targeted by nonsense-mediated decay (NMD) are upregulated. Mechanistically, recruiting CASC3 to reporter mRNAs by direct tethering or via binding to the EJC stimulates mRNA decay and endonucleolytic cleavage at the termination codon. Building on existing EJC-NMD models, we propose that CASC3 equips the EJC with the ability to communicate with the NMD machinery in the cytoplasm. Collectively, our results characterize CASC3 as a peripheral EJC protein that tailors the transcriptome by promoting the degradation of EJC-dependent NMD substrates.

scholarly journals Readthrough of stop codons under limiting ABCE1 concentration involves frameshifting and inhibits nonsense-mediated mRNA decay

2020 ◽  
Vol 48 (18) ◽  
pp. 10259-10279
Author(s):  
Giuditta Annibaldis ◽  
Michal Domanski ◽  
René Dreos ◽  
Lara Contu ◽  
Sarah Carl ◽  
...  
Keyword(s):  
Quality Control ◽  
Mrna Decay ◽  
Translation Termination ◽  
Human Cells ◽  
Ribosome Recycling Factor ◽  
Ribosome Stalling ◽  
Endonucleolytic Cleavage ◽  
Nonsense Mediated Mrna Decay ◽  
Insight Into ◽  
Reading Frames

Abstract To gain insight into the mechanistic link between translation termination and nonsense-mediated mRNA decay (NMD), we depleted the ribosome recycling factor ABCE1 in human cells, resulting in an upregulation of NMD-sensitive mRNAs. Suppression of NMD on these mRNAs occurs prior to their SMG6-mediated endonucleolytic cleavage. ABCE1 depletion caused ribosome stalling at termination codons (TCs) and increased ribosome occupancy in 3′ UTRs, implying enhanced TC readthrough. ABCE1 knockdown indeed increased the rate of readthrough and continuation of translation in different reading frames, providing a possible explanation for the observed NMD inhibition, since enhanced readthrough displaces NMD activating proteins from the 3′ UTR. Our results indicate that stalling at TCs triggers ribosome collisions and activates ribosome quality control. Collectively, we show that improper translation termination can lead to readthrough of the TC, presumably due to ribosome collisions pushing the stalled ribosomes into the 3′ UTR, where it can resume translation in-frame as well as out-of-frame.

scholarly journals SMG5-SMG7 authorize nonsense-mediated mRNA decay by enabling SMG6 endonucleolytic activity

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Volker Boehm ◽  
Sabrina Kueckelmann ◽  
Jennifer V. Gerbracht ◽  
Sebastian Kallabis ◽  
Thiago Britto-Borges ◽  
...  
Keyword(s):  
Mrna Decay ◽  
Translation Termination ◽  
Mrna Degradation ◽  
Functional Connection ◽  
Eukaryotic Gene Expression ◽  
Eukaryotic Gene ◽  
Nonsense Mediated Mrna Decay ◽  
Improved Model ◽  
Dependent Pathway

AbstractEukaryotic gene expression is constantly controlled by the translation-coupled nonsense-mediated mRNA decay (NMD) pathway. Aberrant translation termination leads to NMD activation, resulting in phosphorylation of the central NMD factor UPF1 and robust clearance of NMD targets via two seemingly independent and redundant mRNA degradation branches. Here, we uncover that the loss of the first SMG5-SMG7-dependent pathway also inactivates the second SMG6-dependent branch, indicating an unexpected functional connection between the final NMD steps. Transcriptome-wide analyses of SMG5-SMG7-depleted cells confirm exhaustive NMD inhibition resulting in massive transcriptomic alterations. Intriguingly, we find that the functionally underestimated SMG5 can substitute the role of SMG7 and individually activate NMD. Furthermore, the presence of either SMG5 or SMG7 is sufficient to support SMG6-mediated endonucleolysis of NMD targets. Our data support an improved model for NMD execution that features two-factor authentication involving UPF1 phosphorylation and SMG5-SMG7 recruitment to access SMG6 activity.

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