Autoregulated Splicing of muscleblind-like 1 (MBNL1) Pre-mRNA

• Published in: The Journal of biological chemistry Vol. 286; no. 39; pp. 34224 - 34233
• Main Authors: Gates, Devika P., Coonrod, Leslie A., Berglund, J. Andrew
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 30-09-2011; American Society for Biochemistry and Molecular Biology
• Subjects: Exons - physiology; HeLa Cells; Humans; Introns - physiology; Response Elements - physiology; RNA; RNA Precursors - biosynthesis; RNA Precursors - genetics; RNA Splice Sites - physiology; RNA Splicing; RNA Splicing - physiology; RNA Structure; RNA-binding Protein; RNA-Binding Proteins - biosynthesis; RNA-Binding Proteins - genetics; Zinc; RNA Splicing; RNA-binding Protein; RNA; Zinc; RNA Structure
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M111.236547

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.