MBNL1 binds GC motifs embedded in pyrimidines to regulate alternative splicing

Area of Science:

• Molecular Biology
• RNA Splicing
• Genetic Diseases

Background:

• Muscleblind-like 1 (MBNL1) is central to alternative splicing and myotonic dystrophy (DM) pathogenesis.
• In DM, MBNL1 sequestration by repeat RNAs causes splicing defects and disease symptoms.

Purpose of the Study:

• To identify the RNA-binding motif of MBNL1.
• To elucidate MBNL1's role in DM and alternative splicing regulation.

Main Methods:

• Doped SELEX (Systematic Evolution of Ligands by Exponential Enrichment) was employed to identify MBNL1 RNA-binding preferences.
• Splicing reporter assays were used to test MBNL1 regulation mediated by identified motifs.
• Bioinformatic analysis searched for motif enrichment in DM-associated pre-mRNAs.

Main Results:

• SELEX identified pyrimidine-rich RNAs with YGCY motifs as MBNL1 targets.
• Incorporating YGCY motifs into reporters conferred MBNL1-dependent splicing regulation.
• MBNL1 regulates ATP2A1 pre-mRNA splicing via YGCY motifs, relevant to DM.
• YGCY motifs show distinct intronic enrichment patterns upstream/downstream of alternatively spliced exons in DM1.

Conclusions:

• The YGCY motif is a key RNA-binding element for MBNL1.
• This motif is implicated in MBNL1's function and its dysregulation in myotonic dystrophy.
• Understanding MBNL1-RNA interactions provides insights into DM mechanisms and potential therapeutic targets.