title: The SPF27 homologue Num1 connects splicing and kinesin 1-dependent cytoplasmic trafficking in Ustilago maydis.
abstract: The conserved NineTeen protein complex (NTC) is an integral subunit of the spliceosome and required for intron removal during pre-mRNA splicing. The complex associates with the spliceosome and participates in the regulation of conformational changes of core spliceosomal components, stabilizing RNA-RNA- as well as RNA-protein interactions. In addition, the NTC is involved in cell cycle checkpoint control, response to DNA damage, as well as formation and export of mRNP-particles. We have identified the Num1 protein as the homologue of SPF27, one of NTC core components, in the basidiomycetous fungus Ustilago maydis. Num1 is required for polarized growth of the fungal hyphae, and, in line with the described NTC functions, the num1 mutation affects the cell cycle and cell division. The num1 deletion influences splicing in U. maydis on a global scale, as RNA-Seq analysis revealed increased intron retention rates. Surprisingly, we identified in a screen for Num1 interacting proteins not only NTC core components as Prp19 and Cef1, but several proteins with putative functions during vesicle-mediated transport processes. Among others, Num1 interacts with the motor protein Kin1 in the cytoplasm. Similar phenotypes with respect to filamentous and polar growth, vacuolar morphology, as well as the motility of early endosomes corroborate the genetic interaction between Num1 and Kin1. Our data implicate a previously unidentified connection between a component of the splicing machinery and cytoplasmic transport processes. As the num1 deletion also affects cytoplasmic mRNA transport, the protein may constitute a novel functional interconnection between the two disparate processes of splicing and trafficking.
authors.affiliation: Karlsruhe Institute of Technology, Institute for Applied Biosciences, Department of Genetics, Karlsruhe, Germany.
authors.forename: Nikola
authors.initials: N
authors.lastname: Kellner
authors.affiliation: Karlsruhe Institute of Technology, Institute for Applied Biosciences, Department of Genetics, Karlsruhe, Germany ; Georg-August-University-Göttingen, Institute for Microbiology and Genetics, Microbial Cell Biology, Göttingen, Germany.
authors.forename: Kai
authors.initials: K
authors.lastname: Heimel
authors.affiliation: Karlsruhe Institute of Technology, Institute for Applied Biosciences, Department of Genetics, Karlsruhe, Germany.
authors.forename: Theresa
authors.initials: T
authors.lastname: Obhof
authors.affiliation: Institute for Molecular Biology and Tumor Research, Marburg, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Finkernagel
authors.affiliation: Karlsruhe Institute of Technology, Institute for Applied Biosciences, Department of Genetics, Karlsruhe, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Kämper
mesh_terms: D017398:Alternative Splicing / Q000235:genetics*; D001692:Biological Transport / Q000235:genetics; D002352:Carrier Proteins / Q000235:genetics*; D059447:Cell Cycle Checkpoints / Q000235:genetics*; D018797:Cell Cycle Proteins / Q000235:genetics*; D003598:Cytoskeletal Proteins / Q000235:genetics; D004249:DNA Damage / Q000235:genetics; D005656:Fungal Proteins / Q000096:biosynthesis / Q000235:genetics*; D025301:Hyphae / Q000254:growth & development; D016547:Kinesins / Q000096:biosynthesis / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D016601:RNA-Binding Proteins / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics; D017381:Spliceosomes / Q000235:genetics; D014588:Ustilago / Q000235:genetics* / Q000254:growth & development
chemical_list: D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D003598:Cytoskeletal Proteins; D005656:Fungal Proteins; C107102:KIN1 protein, Ustilago maydis; C071961:NUM1 protein, S cerevisiae; D016601:RNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; D016547:Kinesins