title: A conserved motif controls nuclear localization of Drosophila Muscleblind.
abstract: Human Muscleblind-like proteins are alternative splicing regulators that are functionally altered in the RNA-mediated disease myotonic dystrophy. There are different Muscleblind protein isoforms in Drosophila and we previously determined that these have different subcellular localizations in the COS-M6 cell line. Here, we describe the conservation of the sequence motif KRAEK in isoforms C and E and propose a specific function for this motif. Different Muscleblind isoforms localize to the peri-plasma membrane (MblA), cytoplasm (MblB), or show no preference for the nuclear or cytoplasmic compartment (MblC and MblD) in Drosophila S2 cells transiently transfected with Musclebind expression plasmids. Mutation of the KRAEK motif reduces MblC nuclear localization, whereas fusion of a single KRAEK motif to the heterologous protein beta-galactosidase is sufficient to target the reporter protein to the nucleus of S2 cells. This motif is not exclusive to Muscleblind proteins and is detected in several other protein types. Taken together, these results suggest that the KRAEK motif regulates nuclear translocation of Muscleblind and may constitute a new class of nuclear localization signal.
authors.affiliation: Department of Genetics, University of Valencia, Valencia, Spain.
authors.forename: Juan M
authors.initials: JM
authors.lastname: Fernandez-Costa
authors.forename: Ruben
authors.initials: R
authors.lastname: Artero
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D017124:Conserved Sequence; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000235:genetics* / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D020033:Protein Isoforms; D013347:Subcellular Fractions / Q000378:metabolism; D014162:Transfection; D016335:Zinc Fingers
chemical_list: D029721:Drosophila Proteins; D009687:Nuclear Proteins; D020033:Protein Isoforms; C109271:mbl protein, Drosophila