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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    • "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.
    Journal of cystic fibrosis: official journal of the European Cystic Fibrosis Society 04/2013; 12(6). DOI:10.1016/j.jcf.2013.03.007 · 3.48 Impact Factor
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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].
    BMB reports 01/2013; 46(1):9-16. DOI:10.5483/BMBRep.2013.46.1.002 · 2.60 Impact Factor
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    • "There is also evidence to suggest that NMD efficiency varies between different people with the same mutation [56,57], between different tissue types within an organism [58,59], and even between different strains of the same cell type [60]. It is possible that variable efficiencies of NMD can influence the clinical outcome of hereditary and acquired genetic disease and thus act as a genetic modifier of human genetic diseases. "
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    ABSTRACT: Identification of novel, highly penetrant, breast cancer susceptibility genes will require the application of additional strategies beyond that of traditional linkage and candidate gene approaches. Approximately one-third of inherited genetic diseases, including breast cancer susceptibility, are caused by frameshift or nonsense mutations that truncate the protein product 1. Transcripts harbouring premature termination codons are selectively and rapidly degraded by the nonsense-mediated mRNA decay (NMD) pathway. Blocking the NMD pathway in any given cell will stabilise these mutant transcripts, which can then be detected using gene expression microarrays. This technique, known as gene identification by nonsense-mediated mRNA decay inhibition (GINI), has proved successful in identifying sporadic nonsense mutations involved in many different cancer types. However, the approach has not yet been applied to identify germline mutations involved in breast cancer. We therefore attempted to use GINI on lymphoblastoid cell lines (LCLs) from multiple-case, non- BRCA1/2 breast cancer families in order to identify additional high-risk breast cancer susceptibility genes. We applied GINI to a total of 24 LCLs, established from breast-cancer affected and unaffected women from three multiple-case non-BRCA1/2 breast cancer families. We then used Illumina gene expression microarrays to identify transcripts stabilised by the NMD inhibition. The expression profiling identified a total of eight candidate genes from these three families. One gene, PPARGC1A, was a candidate in two separate families. We performed semi-quantitative real-time reverse transcriptase PCR of all candidate genes but only PPARGC1A showed successful validation by being stabilised in individuals with breast cancer but not in many unaffected members of the same family. Sanger sequencing of all coding and splice site regions of PPARGC1A did not reveal any protein truncating mutations. Haplotype analysis using short tandem repeat microsatellite markers did not indicate the presence of a haplotype around PPARGC1A which segregated with disease in the family. The application of the GINI method to LCLs to identify transcripts harbouring germline truncating mutations is challenging due to a number of factors related to cell type, microarray sensitivity and variations in NMD efficiency.
    BMC Cancer 06/2012; 12(1):246. DOI:10.1186/1471-2407-12-246 · 3.36 Impact Factor
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