scholarly journals LQT2 nonsense mutations generate trafficking defective NH2-terminally truncated channels by the reinitiation of translation

2013 ◽  
Vol 305 (9) ◽  
pp. H1397-H1404 ◽  
Author(s):  
Matthew R. Stump ◽  
Qiuming Gong ◽  
Zhengfeng Zhou
Keyword(s):  
Ventricular Arrhythmias ◽  
Premature Termination Codon ◽  
Wild Type ◽  
Autosomal Dominant Disorder ◽  
Nonsense Mutations ◽  
Accelerated Degradation ◽  
Herg Current ◽  
Nonsense Mediated Mrna Decay ◽  
Herg Channels

The human ether-a-go-go-related gene ( hERG) encodes a voltage-activated K+ channel that contributes to the repolarization of the cardiac action potential. Long QT syndrome type 2 (LQT2) is an autosomal dominant disorder caused by mutations in hERG, and patients with LQT2 are susceptible to severe ventricular arrhythmias. We have previously shown that nonsense and frameshift LQT2 mutations caused a decrease in mutant mRNA by the nonsense-mediated mRNA decay (NMD) pathway. The Q81X nonsense mutation was recently found to be resistant to NMD. Translation of Q81X is reinitiated at Met124, resulting in the generation of NH2-terminally truncated hERG channels with altered gating properties. In the present study, we identified two additional NMD-resistant LQT2 nonsense mutations, C39X and C44X, in which translation is reinitiated at Met60. Deletion of the first 59 residues of the channel truncated nearly one-third of the highly structured Per-Arnt-Sim domain and resulted in the generation of trafficking-defective proteins and a complete loss of hERG current. Partial deletion of the Per-Arnt-Sim domain also resulted in the accelerated degradation of the mutant channel proteins. The coexpression of mutant and wild-type channels did not significantly disrupt the function and trafficking properties of wild-type hERG. Our present findings indicate that translation reinitiation may generate trafficking-defective as well as dysfunctional channels in patients with LQT2 premature termination codon mutations that occur early in the coding sequence.

scholarly journals Screening Readthrough Compounds to Suppress Nonsense Mutations: Possible Application to β-Thalassemia

2020 ◽  
Vol 9 (2) ◽  
pp. 289 ◽  
Author(s):  
Monica Borgatti ◽  
Emiliano Altamura ◽  
Francesca Salvatori ◽  
Elisabetta D’Aversa ◽  
Nicola Altamura
Keyword(s):  
Genetic Disease ◽  
Chelation Therapy ◽  
Translation Termination ◽  
Premature Termination Codon ◽  
Nonsense Suppression ◽  
Current Status ◽  
Nonsense Mutations ◽  
Nonsense Mediated Mrna Decay ◽  
Mrna Destabilization ◽  
Premature Translation Termination

Several types of thalassemia (including β039-thalassemia) are caused by nonsense mutations in genes controlling globin production, leading to premature translation termination and mRNA destabilization mediated by the nonsense mediated mRNA decay. Drugs (for instance, aminoglycosides) can be designed to suppress premature translation termination by inducing readthrough (or nonsense suppression) at the premature termination codon. These findings have introduced new hopes for the development of a pharmacologic approach to cure this genetic disease. In the present review, we first summarize the principle and current status of the chemical relief for the expression of functional proteins from genes otherwise unfruitful for the presence of nonsense mutations. Second, we compare data available on readthrough molecules for β0-thalassemia. The examples reported in the review strongly suggest that ribosomal readthrough should be considered as a therapeutic approach for the treatment of β0-thalassemia caused by nonsense mutations. Concluding, the discovery of molecules, exhibiting the property of inducing β-globin, such as readthrough compounds, is of great interest and represents a hope for several patients, whose survival will depend on the possible use of drugs rendering blood transfusion and chelation therapy unnecessary.

The nuclear cap-binding protein complex is not essential for nonsense-mediated mRNA decay (NMD) in plants.

2008 ◽  
Vol 55 (4) ◽  
pp. 825-828 ◽  
Author(s):  
Agnieszka Dzikiewicz-Krawczyk ◽  
Paulina Piontek ◽  
Zofia Szweykowska-Kulińska ◽  
Artur Jarmołowski
Keyword(s):  
Protein Complex ◽  
Mrna Decay ◽  
Splice Variants ◽  
Binding Protein ◽  
Direct Sequencing ◽  
Premature Termination Codon ◽  
Wild Type ◽  
Mrna Variants ◽  
Nonsense Mediated Mrna Decay ◽  
Alternatively Spliced

In this study we investigated whether in plants, like in mammals, components of the nuclear cap-binding protein complex (CBC) are involved in nonsense-mediated mRNA decay (NMD). We selected several genes producing at least two alternatively spliced mRNA variants: one with a premature termination codon (PTC+) and another without it (PTC-). For each gene the PTC+/PTC- ratio was calculated using RT-PCR and direct sequencing in four Arabidopsis thaliana lines: wild type, the NMD mutant atupf3-1 and two CBC mutants: cbp20 and abh1. Whereas in the NMD mutant the ratios of PTC+/PTC- splice variants were higher than in wild-type plants, the two CBC mutants investigated showed no change in the PTC+/PTC- ratios. Our results suggest that neither CBP20 nor CBP80 is involved in NMD in A. thaliana.

scholarly journals Suppression of aminoglycoside-induced premature termination codon readthrough by the TRP channel inhibitor AC1903

2021 ◽  
Author(s):  
Alireza Baradaran-Heravi ◽  
Claudia C Bauer ◽  
Isabelle B Pickles ◽  
Sara Hosseini-Farahabadi ◽  
Aruna Balgi ◽  
...  
Keyword(s):  
Premature Termination ◽  
Genetic Disorders ◽  
Premature Termination Codon ◽  
Cation Channels ◽  
Trpc Channels ◽  
Nonsense Mutations ◽  
Variable Effect ◽  
Premature Termination Codons ◽  
Ic50 Values ◽  
Nonsense Mediated Mrna Decay

Nonsense mutations, which occur in ~11% of patients with genetic disorders, introduce premature termination codons (PTCs) that lead to truncated proteins and promote nonsense-mediated mRNA decay. Aminoglycosides such as gentamicin and G418 permit PTC readthrough and so may address this problem. However, their effects are variable between patients, making clinical use of aminoglycosides challenging. In this study, we addressed the hypothesis that TRP non-selective cation channels contribute to the variable effect of aminoglycosides by controlling their cellular uptake. To attempt to identify the channel type involved, we tested AC1903, a 2-aminobenzimidazole derivative recently reported to selectively inhibit TRPC5 cation channels. AC1903 consistently suppressed G418 uptake and G418-induced PTC readthrough in the DMS-114 cell line and patient-derived JEB01 keratinocytes. In an effort to validate the suggested role of TRPC5, we tested an independent and more potent inhibitor called Pico145, which affects channels containing TRPC1, TRPC4 and TRPC5 but not other TRPCs or other channels. Unexpectedly, Pico145 was completely without effect, suggesting that AC1903 may work through other or additional targets. Consistent with this suggestion, AC1903 inhibited multiple TRPC channels including homomeric TRPC3, TRPC4, TRPC5, TRPC6 as well as concatemeric TRPC4-C1 and TRPC5-C1 channels, all with low micromolar IC50 values. It also inhibited TRPV4 channels but had weak or no effects on TRPV1 and no effect on another non-selective cation channel, PIEZO1. Overall, our study reveals a suppressor of aminoglycoside-mediated PTC readthrough (i.e., AC1903) but suggests that this compound has previously unrecognised effects. These effects require further investigation to determine the molecular mechanism by which AC1903 suppresses aminoglycoside uptake and PTC readthrough.

scholarly journals Progressive polysomal association of Upf1, Upf2, and Upf3 as ribosomes traverse mRNA coding regions

2021 ◽  
Author(s):  
Robin Ganesan ◽  
Kotchaphorn Mangkalaphiban ◽  
Richard E. Baker ◽  
Feng He ◽  
Allan Jacobson
Keyword(s):  
Mrna Translation ◽  
Premature Termination Codon ◽  
Ribosome Profiling ◽  
Yeast Genetics ◽  
Wild Type ◽  
Ribosome Binding ◽  
Coding Regions ◽  
Mrna Surveillance ◽  
Nonsense Mediated Mrna Decay

SUMMARYUpf1, Upf2, and Upf3 are the central regulators of nonsense-mediated mRNA decay (NMD), the eukaryotic mRNA quality control pathway generally triggered when a premature termination codon is recognized by the ribosome. The NMD-related functions of the Upf proteins likely commence while these factors are ribosome-associated, but little is known of the timing of their ribosome binding, their specificity for ribosomes translating NMD substrates, or the nature and role of any ribosome:Upf complexes. Here, we have elucidated details of the ribosome-associated steps of NMD. By combining yeast genetics with selective ribosome profiling and co-sedimentation analyses of polysomes with wild-type and mutant Upf proteins, our approaches have identified distinct states of ribosome:Upf association. All three Upf factors manifest progressive polysome association as mRNA translation proceeds, but these events appear to be preceded by formation of a Upf1:80S complex as mRNAs initiate translation. This complex is likely executing an early mRNA surveillance function.

scholarly journals Nonrecombinant meiosis I nondisjunction in Saccharomyces cerevisiae induced by tRNA ochre suppressors.

Genetics ◽  
1989 ◽  
Vol 123 (1) ◽  
pp. 81-95 ◽  
Author(s):  
E J Louis ◽  
J E Haber
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mitotic Chromosome ◽  
Stop Codon ◽  
Fold Increase ◽  
Wild Type ◽  
Yeast Saccharomyces Cerevisiae ◽  
Nonsense Mutations ◽  
Chromosome Iii ◽  
Meiosis I ◽  
Chromosome Nondisjunction

Abstract The presence of the tRNA ochre suppressors SUP11 and SUP5 is found to induce meiosis I nondisjunction in the yeast Saccharomyces cerevisiae. The induction increases with increasing dosage of the suppressor and decreases in the presence of an antisuppressor. The effect is independent of the chromosomal location of SUP11. Each of five different chromosomes monitored exhibited nondisjunction at frequencies of 0.1%-1.1% of random spores, which is a 16-160-fold increase over wild-type levels. Increased nondisjunction is reflected by a marked increase in tetrads with two and zero viable spores. In the case of chromosome III, for which a 50-cM map interval was monitored, the resulting disomes are all in the parental nonrecombinant configuration. Recombination along chromosome III appears normal both in meioses that have no nondisjunction and in meioses for which there was nondisjunction of another chromosome. We propose that a proportion of one or more proteins involved in chromosome pairing, recombination or segregation are aberrant due to translational read-through of the normal ochre stop codon. Hygromycin B, an antibiotic that can suppress nonsense mutations via translational read-through, also induces nonrecombinant meiosis I nondisjunction. Increases in mistranslation, therefore, increase the production of aneuploids during meiosis. There was no observable effect of SUP11 on mitotic chromosome nondisjunction; however some disomes caused SUP11 ade2-ochre strains to appear white or red, instead of pink.

Discovery of natural product ovalicin sensitive type 1 methionine aminopeptidases: molecular and structural basis

2019 ◽  
Vol 476 (6) ◽  
pp. 991-1003 ◽  
Author(s):  
Vijaykumar Pillalamarri ◽  
Tarun Arya ◽  
Neshatul Haque ◽  
Sandeep Chowdary Bala ◽  
Anil Kumar Marapaka ◽  
...  
Keyword(s):  
Natural Product ◽  
Active Site ◽  
Covalent Modification ◽  
Structural Basis ◽  
Wild Type ◽  
Methionine Aminopeptidases ◽  
Synthetic Derivative ◽  
Dynamics Simulations

Abstract Natural product ovalicin and its synthetic derivative TNP-470 have been extensively studied for their antiangiogenic property, and the later reached phase 3 clinical trials. They covalently modify the conserved histidine in Type 2 methionine aminopeptidases (MetAPs) at nanomolar concentrations. Even though a similar mechanism is possible in Type 1 human MetAP, it is inhibited only at millimolar concentration. In this study, we have discovered two Type 1 wild-type MetAPs (Streptococcus pneumoniae and Enterococcus faecalis) that are inhibited at low micromolar to nanomolar concentrations and established the molecular mechanism. F309 in the active site of Type 1 human MetAP (HsMetAP1b) seems to be the key to the resistance, while newly identified ovalicin sensitive Type 1 MetAPs have a methionine or isoleucine at this position. Type 2 human MetAP (HsMetAP2) also has isoleucine (I338) in the analogous position. Ovalicin inhibited F309M and F309I mutants of human MetAP1b at low micromolar concentration. Molecular dynamics simulations suggest that ovalicin is not stably placed in the active site of wild-type MetAP1b before the covalent modification. In the case of F309M mutant and human Type 2 MetAP, molecule spends more time in the active site providing time for covalent modification.

Induction of an Antitumoral Immune Response by Wild-Type Adeno-Associated Virus Type 2 in an In Vivo Model of Pancreatic Carcinoma

Pancreas ◽  
2007 ◽  
Vol 35 (1) ◽  
pp. 63-72 ◽  
Author(s):  
Sven Eisold ◽  
Jan Schmidt ◽  
Eduard Ryschich ◽  
Michael Gock ◽  
Ernst Klar ◽  
...  
Keyword(s):  
Immune Response ◽  
Pancreatic Carcinoma ◽  
Virus Type ◽  
In Vivo Model ◽  
Wild Type ◽  
Adeno Associated Virus

scholarly journals Identification and characterization of a sequence motif involved in nonsense-mediated mRNA decay.

1995 ◽  
Vol 15 (4) ◽  
pp. 2231-2244 ◽  
Author(s):  
S Zhang ◽  
M J Ruiz-Echevarria ◽  
Y Quan ◽  
S W Peltz
Keyword(s):  
Mrna Decay ◽  
Sequence Motif ◽  
Nonsense Mutations ◽  
Stem Loop ◽  
Cis Acting ◽  
Stem Loop Structure ◽  
Nonsense Codon ◽  
Nonsense Mediated Mrna Decay

In both prokaryotes and eukaryotes, nonsense mutations in a gene can enhance the decay rate or reduce the abundance of the mRNA transcribed from that gene, and we call this process nonsense-mediated mRNA decay. We have been investigating the cis-acting sequences involved in this decay pathway. Previous experiments have demonstrated that, in addition to a nonsense codon, specific sequences 3' of a nonsense mutation, which have been defined as downstream elements, are required for mRNA destabilization. The results presented here identify a sequence motif (TGYYGATGYYYYY, where Y stands for either T or C) that can predict regions in genes that, when positioned 3' of a nonsense codon, promote rapid decay of its mRNA. Sequences harboring two copies of the motif from five regions in the PGK1, ADE3, and HIS4 genes were able to function as downstream elements. In addition, four copies of this motif can function as an independent downstream element. The sequences flanking the motif played a more significant role in modulating its activity when fewer copies of the sequence motif were present. Our results indicate the sequences 5' of the motif can modulate its activity by maintaining a certain distance between the sequence motif and the termination codon. We also suggest that the sequences 3' of the motif modulate the activity of the downstream element by forming RNA secondary structures. Consistent with this view, a stem-loop structure positioned 3' of the sequence motif can enhance the activity of the downstream element. This sequence motif is one of the few elements that have been identified that can predict regions in genes that can be involved in mRNA turnover. The role of these sequences in mRNA decay is discussed.

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