Modulation of survival motor neuron pre-mRNA splicing by inhibition of alternative 3' splice site pairing.
Spinal muscular atrophy is caused by the loss of functional survival motor neuron (SMN1) alleles. A translationally silent nucleotide transition in the duplicated copy of the gene (SMN2) leads to exon 7 skipping and expression of a nonfunctional gene product. It has been suggested that differential SMN2 splicing is caused by the disruption of an exonic splicing enhancer. Here we show that the single nucleotide difference reduces the intrinsic strength of the 3' splice site of exon 7 2-fold, whereas the strength of the 5' splice site of the exon 7 is not affected. Thus, a decrease in splice site strength is magnified in the context of competing exons. These data suggest that lower levels of exon 7 definition not only reduce intron 6 removal but, more importantly, increase the efficiency of the competing exon 7 skipping pathway. Antisense oligonucleotides were tested to modulate exon 7 inclusion, which contains the authentic translation stop codon. Oligonucleotides directed toward the 3' splice site of exon 8 were shown to alter SMN2 splicing in favor of exon 7 inclusion. These results suggest that antisense oligonucleotides could be used as a therapeutic strategy to counteract the progression of SMA.
Lim
S R
SR
Department of Microbiology and Molecular Genetics, College of Medicine, University of California, Irvine, California 92697-4025, USA.
Hertel
K J
KJ
D000483:Alleles; D001483:Base Sequence; D002460:Cell Line; D017362:Cyclic AMP Response Element-Binding Protein; D004305:Dose-Response Relationship, Drug; D005091:Exons; D006801:Humans; D007438:Introns; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D014176:Protein Biosynthesis; D012326:RNA Splicing; D012333:RNA, Messenger / Q000378:metabolism*; D016601:RNA-Binding Proteins; D055532:SMN Complex Proteins; D055533:Survival of Motor Neuron 1 Protein; D055540:Survival of Motor Neuron 2 Protein; D013997:Time Factors; D014407:Tumor Cells, Cultured
D017362:Cyclic AMP Response Element-Binding Protein; D009419:Nerve Tissue Proteins; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D055532:SMN Complex Proteins; C526471:SMN1 protein, human; C526477:SMN2 protein, human; D055533:Survival of Motor Neuron 1 Protein; D055540:Survival of Motor Neuron 2 Protein