The canonical UPF1-dependent nonsense-mediated mRNA decay is inhibited in transcripts carrying a short open reading frame independent of sequence context.
Nonsense-mediated mRNA decay (NMD) is a surveillance mechanism that degrades mRNAs carrying premature translation termination codons. Generally, NMD is elicited if translation terminates >50-54 nucleotides (nt) upstream of an exon-exon junction. We have previously reported that human beta-globin mRNAs carrying 5'-proximal nonsense mutations (e.g., beta15) accumulate to normal levels, suggesting an exception to the "50-54-nt boundary rule." In the present report, we demonstrate that the strength of the UPF1-dependent NMD of mutant beta-globin mRNAs is specifically determined by the proximity of the nonsense codon to the initiation AUG. This conclusion is supported by a parallel effect of the short ORF size on NMD of nonsense-containing alpha-globin mRNAs. To determine whether the short-ORF effect on NMD response is conserved in heterologous transcripts, we assessed its effects on a set of beta-globin/triosephosphate isomerase (TPI) hybrid mRNAs and on the TPI mRNA. Our data support the conclusion that nonsense mutations resulting in a short ORF are able to circumvent the full activity of the canonical UPF1-dependent NMD pathway.
Silva
Ana Luísa
AL
Centro de Genética Humana, Instituto Nacional de Saúde Dr. Ricardo Jorge, 1649-016 Lisboa, Portugal.
Pereira
Francisco J C
FJ
Morgado
Ana
A
Kong
Jian
J
Martins
Rute
R
Faustino
Paula
P
Liebhaber
Stephen A
SA
Romão
Luísa
L
D020121:5' Untranslated Regions; D000818:Animals; D018387:Codon, Initiator; D018389:Codon, Nonsense; D005914:Globins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D051379:Mice; D016366:Open Reading Frames; D014176:Protein Biosynthesis; D020365:RNA Helicases; D020871:RNA Stability; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D014305:Triose-Phosphate Isomerase / Q000235:genetics / Q000378:metabolism
D020121:5' Untranslated Regions; D018387:Codon, Initiator; D018389:Codon, Nonsense; D011994:Recombinant Proteins; D015534:Trans-Activators; D005914:Globins; D020365:RNA Helicases; C101828:UPF1 protein, human; D014305:Triose-Phosphate Isomerase