title: Inhibition of spliceosome assembly by the cell cycle-regulated protein kinase MELK and involvement of splicing factor NIPP1.
abstract: NIPP1 is a ubiquitous nuclear protein that is required for spliceosome assembly. We report here that the phosphothreonine-binding Forkhead-associated domain of NIPP1 interacts with the cell cycle-regulated protein Ser/Thr kinase MELK (maternal embryonic leucine zipper kinase). The NIPP1-MELK interaction was critically dependent on the phosphorylaton of Thr-478 of MELK and was increased in lysates from mitotically arrested cells. Recombinant MELK was a potent inhibitor of an early step of spliceosome assembly in nuclear extracts. This splicing defect was also seen with a kinase-dead mutant but was absent after mutation (T478A) of the NIPP1 binding site of MELK, indicating a mediatory role for NIPP1. Our data suggest that MELK has a role in the cell cycle-regulated control of pre-mRNA splicing.
authors.affiliation: Afdeling Biochemie, Faculteit Geneeskunde, Catholic University of Leuven, B-3000 Leuven, Belgium.
authors.forename: Veerle
authors.initials: V
authors.lastname: Vulsteke
authors.forename: Monique
authors.initials: M
authors.lastname: Beullens
authors.forename: An
authors.initials: A
authors.lastname: Boudrez
authors.forename: Stefaan
authors.initials: S
authors.lastname: Keppens
authors.forename: Aleyde
authors.initials: A
authors.lastname: Van Eynde
authors.forename: Mark H
authors.initials: MH
authors.lastname: Rider
authors.forename: Willy
authors.initials: W
authors.lastname: Stalmans
authors.forename: Mathieu
authors.initials: M
authors.lastname: Bollen
mesh_terms: D000818:Animals; D019556:COS Cells; D002352:Carrier Proteins / Q000378:metabolism*; D002453:Cell Cycle / Q000502:physiology; D004722:Endoribonucleases; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D010749:Phosphoprotein Phosphatases; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D012322:RNA Precursors / Q000502:physiology; D012326:RNA Splicing; D016601:RNA-Binding Proteins; D017381:Spliceosomes / Q000502:physiology*
chemical_list: D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D012322:RNA Precursors; D016601:RNA-Binding Proteins; C021042:protein phosphatase inhibitor-1; C108524:Melk protein, mouse; D017346:Protein Serine-Threonine Kinases; D004722:Endoribonucleases; D010749:Phosphoprotein Phosphatases; C097081:PPP1R8 protein, human