The efficiency of nonsense-mediated mRNA decay is an inherent character and varies among different cells

Department of Genetics, Life Sciences Institute, The Hebrew University, Jerusalem, Israel.
European Journal of HumanGenetics (Impact Factor: 4.35). 12/2007; 15(11):1156-62. DOI: 10.1038/sj.ejhg.5201889
Source: PubMed


Nonsense-mediated mRNA decay (NMD) is a mechanism, which selectively degrades transcripts carrying premature termination codons (PTCs) and a variety of physiologic transcripts containing NMD-inducing features. In a recent study, we have found variable NMD efficiency among nasal epithelial cells obtained from cystic fibrosis (CF) patients. This variability was found for CF transmembrane conductance regulator (CFTR) transcripts carrying the W1282X PTC, as well as for several NMD physiologic substrates. Here, we aimed to investigate the possibility that variability in NMD efficiency is a more generalized phenomenon and is not restricted to nasal epithelial cells. To investigate this possibility, we analyzed the NMD efficiency of both a CFTR constructs carrying the W1282X PTC and beta-globin constructs carrying the NS39 PTC, in HeLa and MCF7 cells. Variability in NMD efficiency was found for both constructs between the cells, such that in HeLa cells the NMD was highly efficient and in MCF7 the efficiency was significantly lower. Moreover, similar differences in the efficiency of NMD were found for five endogenous NMD physiologic transcripts. Altogether, our results demonstrate existence of cells in which NMD of all transcripts is efficient, whereas others in which the NMD is less efficient, suggesting that the efficiency of NMD is an inherent character of cells. Our results also suggest that variability in the efficiency of NMD is a general phenomenon and is not restricted to nasal epithelial cells. As NMD affects the level of many transcripts, variability in the NMD efficiency might play a role as a genetic modifier of different cellular functions.

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Available from: Gabriele Neu-Yilik, Jun 26, 2014
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    • "Class V: mutations that reduce CFTR protein levels, often by affecting splicing and generating both aberrant mRNA transcripts and a reduced amount of normal mRNA transcripts[4,5]. With this type of mutation it is sometimes challenging to establish their effect on the overall CFTR function and therefore their involvement in the disease, which has a direct and significant impact on genetic counseling[7]. Class VI: mutations that include those that decrease the retention and stability of CFTR at the cell surface. "
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    ABSTRACT: Cystic Fibrosis has attracted much attention in recent years due to significant advances in the pharmacological targeting of the basic defect underlying this recessive disorder: the deficient functional expression of mutant CFTR chloride channels at the apical membrane of epithelial cells. However, increasing evidence points to the reduced efficacy of single treatments, thus reinforcing the need to combine several therapeutic strategies to effectively target the multiple basic defect(s). Protein-repair therapies that use potentiators (activating membrane-located CFTR) or correctors (promoting the relocation of intracellular-retained trafficking mutants of CFTR) in frequent mutations such as F508del and G551D have been put forward and made their way to the clinic with moderate to good efficiency. However, alternative (or additional) approaches targeting the membrane stability of mutant proteins, or correcting the cellular phenotype through direct effect upon other ion channels (affecting the overall electrolyte transport or simply promoting alternative chloride transport) or targeting less frequent mutations (splicing variants, for example), have been proposed and tested in the field of CF. Here, we cover the different strategies that rely on novel findings concerning CFTR interactome and signalosome through which it might be possible to further influence the cellular trafficking and post-translational modification machinery (to increase rescued CFTR abundance and membrane stability). We also highlight the new data on strategies aiming at the regulation of sodium absorption or to increase chloride transport through alternative channels. The development and implementation of these complementary approaches will pave the way to combinatorial therapeutic strategies with increased benefit to CF patients. This article is protected by copyright. All rights reserved.
    Full-text · Article · Sep 2015 · FEBS Journal
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    • "Beside the common F508del variant, our CF patients carry missense and nonsense alterations in the CFTR gene. Indeed, different studies have shown that the effect of nonsense mutations on CFTR mRNA levels are very variable [16] and nonsense-mediated decay (NMD) is addressed as the major mechanism for rapid degradation of aberrant transcripts harboring premature termination codons. Interestingly, microRNAs have recently been defined as important regulators of the NMD efficiency [17]. "
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    ABSTRACT: MicroRNAs (miRNAs) have recently emerged as important gene regulators in Cystic Fibrosis (CF), a common monogenic disease characterized by severe infection and inflammation, especially in the airway compartments. In the current study, we show that both miR-145 and miR-494 are significantly up-regulated in nasal epithelial tissues from CF patients compared with healthy controls (p<0.001 and p<0.01, respectively) by Quantitative Real-Time PCR. Only miR-494 levels showed a trend of correlation with reduced CFTR mRNA expression and positive sweat test values, supporting the negative regulatory role of this miRNA on CFTR synthesis. Using computational prediction algorithms and luciferase reporter assays, SMAD family member 3 (SMAD3), a key element of the TGF-β1 inflammatory pathway, was identified as a target of miR-145. Indeed, miR-145 synthetic mimics suppressed by approximately 40% the expression of a reporter construct containing the SMAD3 3'-UTR. Moreover, we observed an inverse correlation between SMAD3 mRNA expression and miR-145 in CF nasal tissues (r=-0.68, p=0.0018, Pearson's correlation). Taken together, these results confirm the pivotal role of miRNAs in the CF physio-pathogenesis and suggest that miRNA deregulation play a role in the airway disease severity by modulating CFTR levels as well as the expression of important molecules involved in the inflammatory response. miR-494 and miR-145 may, therefore, be potential biomarker and therapeutic target to specific CF clinical manifestations.
    Full-text · Article · Apr 2013 · Journal of cystic fibrosis: official journal of the European Cystic Fibrosis Society
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    • "Since NMD efficiency is known to vary among target transcripts and cell types and NMD machinery does not reduce the level of PTC-containing mRNA to 0% (23,47-54), a small fraction of PTC-containing mRNAs would be resistant to NMD and remain in the cytoplasm. For instance, many reports showed that the abundance of β-globin mRNAs harboring a PTC is reduced to 5-30% of normal level (27,28,34,52,55-61). The remaining NMD-resistant mRNAs, despite being targeted for NMD, would still have EJCs downstream of PTC. "
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    ABSTRACT: In mammalian cells, aberrant transcripts harboring a premature termination codon (PTC) can be generated by abnormal or inefficient biogenesis of mRNAs or by somatic mutation. Truncated polypeptides synthesized from these aberrant transcripts could be toxic to normal cellular functions. However, mammalian cells have evolved sophisticated mechanisms for monitoring the quality of mRNAs. The faulty transcripts harboring PTC are subject to nonsense-mediated mRNA decay (NMD), nonsense-mediated translational repression (NMTR), nonsense-associated alternative splicing (NAS), or nonsense-mediated transcriptional gene silencing (NMTGS). In this review, we briefly outline the molecular characteristics of each pathway and suggest mRNA quality control mechanisms as a means to regulate normal gene expression. [BMB Reports 2013; 46(1): 009-016].
    Full-text · Article · Jan 2013 · BMB reports
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