title: Position of premature termination codons determines susceptibility of hERG mutations to nonsense-mediated mRNA decay in long QT syndrome.
abstract: The degradation of human ether-a-go-go-related gene (hERG, KCNH2) transcripts containing premature termination codon (PTC) mutations by nonsense-mediated mRNA decay (NMD) is an important mechanism of long QT syndrome type 2 (LQT2). The mechanisms governing the recognition of PTC-containing hERG transcripts as NMD substrates have not been established. We used a minigene system to study two frameshift mutations, R1032Gfs 25 and D1037Rfs 82. R1032Gfs 25 introduces a PTC in exon 14, whereas D1037Rfs 82 causes a PTC in the last exon (exon 15). We showed that R1032Gfs 25, but not D1037Rfs 82, reduced the level of mutant mRNA compared to the wild-type minigene in an NMD-dependent manner. The deletion of intron 14 prevented degradation of R1032Gfs 25 mRNA indicating that a downstream intron is required for NMD. The recognition and elimination of PTC-containing transcripts by NMD required that the mutation be positioned >54-60 nt upstream of the 3'-most exon-exon junction. Finally, we used a full-length hERG splicing-competent construct to show that inhibition of downstream intron splicing by antisense morpholino oligonucleotides inhibited NMD and rescued the functional expression of a third LQT2 mutation, Y1078. The present study defines the positional requirements for the susceptibility of LQT2 mutations to NMD and posits that the majority of reported LQT2 nonsense and frameshift mutations are potential targets of NMD.
authors: Knight Cardiovascular Institute, Oregon Health & Science University, Portland, OR, USA.
authors: Qiuming
authors: Q
authors: Gong
authors: Knight Cardiovascular Institute, Oregon Health & Science University, Portland, OR, USA.
authors: Matthew R
authors: MR
authors: Stump
authors: Knight Cardiovascular Institute, Oregon Health & Science University, Portland, OR, USA. Electronic address: zhouzh@ohsu.edu.
authors: Zhengfeng
authors: Z
authors: Zhou
mesh_terms: D018389:Codon, Nonsense / Q000235:genetics*; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D008133:Long QT Syndrome / Q000235:genetics*; D060172:Morpholinos; D009154:Mutation / Q000235:genetics*; D059365:Nonsense Mediated mRNA Decay / Q000235:genetics*; D018408:Patch-Clamp Techniques; D034741:RNA, Small Interfering / Q000235:genetics
chemical_list: D018389:Codon, Nonsense; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human; D060172:Morpholinos; D034741:RNA, Small Interfering
keywords: Arrhythmia; KCNH2; Long QT syndrome; Patch-clamp; Potassium channels