Long Open Reading Frame Transcripts Escape Nonsense-Mediated mRNA Decay in Yeast

• A long 3′ UTR is not sufficient for efficient nonsense-mediated mRNA decay
• Increasing ORF size leads to a stabilization of NMD substrates in yeast
• Upf1 binding to mRNAs with long 3′ UTRs is not affected by transcript size

SummaryNonsense-mediated mRNA decay (NMD) destabilizes eukaryotic transcripts with long 3′ UTRs. To investigate whether other transcript features affect NMD, we generated yeast strains expressing chromosomal-derived mRNAs with 979 different promoter and open reading frame (ORF) regions and with the same long, destabilizing 3′ UTR. We developed a barcode-based DNA microarray strategy to compare the levels of each reporter mRNA in strains with or without active NMD. The size of the coding region had a significant negative effect on NMD efficiency. This effect was not specific to the tested 3′ UTR because two other different NMD reporters became less sensitive to NMD when ORF length was increased. Inefficient NMD was not due to a lack of association of Upf1 to long ORF transcripts. In conclusion, in addition to a long 3′ UTR, short translation length is an important feature of NMD substrates in yeast.

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