title: Autoregulated splicing of muscleblind-like 1 (MBNL1) Pre-mRNA.
abstract: Muscleblind-like 1 (MBNL1) is a splicing factor whose improper cellular localization is a central component of myotonic dystrophy. In myotonic dystrophy, the lack of properly localized MBNL1 leads to missplicing of many pre-mRNAs. One of these events is the aberrant inclusion of exon 5 within the MBNL1 pre-mRNA. The region of the MBNL1 gene that includes exon 5 and flanking intronic sequence is highly conserved in vertebrate genomes. The 3'-end of intron 4 is non-canonical in that it contains a predicted branch point that is 141 nucleotides from the 3'-splice site and an AAG 3'-splice site. Using a minigene that includes exon 4, intron 4, exon 5, intron 5, and exon 6 of MBNL1, we showed that MBNL1 regulates inclusion of exon 5. Mapping of the intron 4 branch point confirmed that branching occurs primarily at the predicted distant branch point. Structure probing and footprinting revealed that the highly conserved region between the branch point and 3'-splice site is primarily unstructured and that MBNL1 binds within this region of the pre-mRNA. Deletion of the MBNL1 response element eliminated MBNL1 splicing regulation and led to complete inclusion of exon 5, which is consistent with the suppressive effect of MBNL1 on splicing.
authors.affiliation: Department of Chemistry and Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403-1229, USA.
authors.forename: Devika P
authors.initials: DP
authors.lastname: Gates
authors.forename: Leslie A
authors.initials: LA
authors.lastname: Coonrod
authors.forename: J Andrew
authors.initials: JA
authors.lastname: Berglund
mesh_terms: D005091:Exons / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D007438:Introns / Q000502:physiology*; D012322:RNA Precursors / Q000096:biosynthesis* / Q000235:genetics; D022821:RNA Splice Sites / Q000502:physiology*; D012326:RNA Splicing / Q000502:physiology*; D016601:RNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D020218:Response Elements / Q000502:physiology
chemical_list: C493663:MBNL1 protein, human; D012322:RNA Precursors; D022821:RNA Splice Sites; D016601:RNA-Binding Proteins