Unspliced Precursors of NMD-Sensitive beta-Globin Transcripts Exhibit Decreased Steady-State Levels in Erythroid Cells

• Type: Article in International Scientific Journal
• Date: 2012

Authors

Morgado, A (Author) Other; Almeida, F (Author) Other; Teixeira, A (Author) Other; Silva, AL (Author) Other; Romao, L (Author) Other

Journal

Title: PLoS ONE

Vol. 7

ISSN: 1932-6203

Publisher: Public Library of Science

Indexing

ISI Web of Knowledge - 2 Citations

Scopus - 2 Citations

Other information

Authenticus ID: P-002-91W

DOI: 10.1371/journal.pone.0038505

Abstract (EN): Nonsense-mediated mRNA decay (NMD) is a quality control mechanism that detects and rapidly degrades mRNAs carrying premature translation-termination codons (PTCs). Mammalian NMD depends on both splicing and translation, and requires recognition of the premature stop codon by the cytoplasmic ribosomes. Surprisingly, some published data have suggested that nonsense codons may also affect the nuclear metabolism of the nonsense-mutated transcripts. To determine if nonsense codons could influence nuclear events, we have directly assessed the steady-state levels of the unspliced transcripts of wild-type and PTC-containing human beta-globin genes stably transfected in mouse erythroleukemia (MEL) cells, after erythroid differentiation induction, or in HeLa cells. Our analyses by ribonuclease protection assays and reverse transcription-coupled quantitative PCR show that beta-globin pre-mRNAs carrying NMD-competent PTCs, but not those containing a NMD-resistant PTC, exhibit a significant decrease in their steady-state levels relatively to the wild-type or to a missense-mutated beta-globin pre-mRNA. On the contrary, in HeLa cells, human beta-globin pre-mRNAs carrying NMD-competent PTCs accumulate at normal levels. Functional analyses of these pre-mRNAs in MEL cells demonstrate that their low steady-state levels do not reflect significantly lower pre-mRNA stabilities when compared to the normal control. Furthermore, our results also provide evidence that the relative splicing efficiencies of intron 1 and 2 are unaffected. This set of data highlights potential nuclear pathways that might be promoter-and/or cell line-specific, which recognize the NMD-sensitive transcripts as abnormal. These specialized nuclear pathway(s) may be superimposed on the general NMD mechanism.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 13