Inhibition of spliceosome assembly by the cell cycle-regulated protein kinase MELK and involvement of splicing factor NIPP1.
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.
Vulsteke
Veerle
V
Afdeling Biochemie, Faculteit Geneeskunde, Catholic University of Leuven, B-3000 Leuven, Belgium.
Beullens
Monique
M
Boudrez
An
A
Keppens
Stefaan
S
Van Eynde
Aleyde
A
Rider
Mark H
MH
Stalmans
Willy
W
Bollen
Mathieu
M
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*
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