title: Mechanistic determinants of MBNL activity.
abstract: Muscleblind-like (MBNL) proteins are critical RNA processing factors in development. MBNL activity is disrupted in the neuromuscular disease myotonic dystrophy type 1 (DM1), due to the instability of a non-coding microsatellite in the DMPK gene and the expression of CUG expansion (CUGexp) RNAs. Pathogenic interactions between MBNL and CUGexpRNA lead to the formation of nuclear complexes termed foci and prevent MBNL function in pre-mRNA processing. The existence of multiple MBNL genes, as well as multiple protein isoforms, raises the question of whether different MBNL proteins possess unique or redundant functions. To address this question, we coexpressed three MBNL paralogs in cells at equivalent levels and characterized both specific and redundant roles of these proteins in alternative splicing and RNA foci dynamics. When coexpressed in the same cells, MBNL1, MBNL2 and MBNL3 bind the same RNA motifs with different affinities. While MBNL1 demonstrated the highest splicing activity, MBNL3 showed the lowest. When forming RNA foci, MBNL1 is the most mobile paralog, while MBNL3 is rather static and the most densely packed on CUGexpRNA. Therefore, our results demonstrate that MBNL paralogs and gene-specific isoforms possess inherent functional differences, an outcome that could be enlisted to improve therapeutic strategies for DM1.
authors.affiliation: Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland lukasz.j.sznajder@gmail.com.
authors.forename: Łukasz J
authors.initials: ŁJ
authors.lastname: Sznajder
authors.affiliation: Department of Molecular and Cellular Biology, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland.
authors.forename: Michał
authors.initials: M
authors.lastname: Michalak
authors.affiliation: Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Taylor
authors.affiliation: Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland.
authors.forename: Piotr
authors.initials: P
authors.lastname: Cywoniuk
authors.affiliation: Department of Bioinformatics, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland.
authors.forename: Michał
authors.initials: M
authors.lastname: Kabza
authors.affiliation: Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Wojtkowiak-Szlachcic
authors.affiliation: Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Matłoka
authors.affiliation: Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland.
authors.forename: Patryk
authors.initials: P
authors.lastname: Konieczny
authors.affiliation: Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland ksobczak@amu.edu.pl.
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Sobczak
mesh_terms: D017398:Alternative Splicing; D001665:Binding Sites; D002460:Cell Line; D005091:Exons; D006801:Humans; D059372:Nucleotide Motifs; D056510:Position-Specific Scoring Matrices; D011485:Protein Binding; D021381:Protein Transport; D012313:RNA / Q000737:chemistry / Q000378:metabolism; D059368:RNA Isoforms; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*
chemical_list: C493663:MBNL1 protein, human; C467324:MBNL3 protein, human; D059368:RNA Isoforms; D016601:RNA-Binding Proteins; D012313:RNA