The oncogenic serine/threonine kinase Pim-1 phosphorylates and inhibits the activity of Cdc25C-associated kinase 1 (C-TAK1): a novel role for Pim-1 at the G2/M cell cycle checkpoint.
The Pim-1 oncogene encodes a serine-threonine kinase that relays signals from cytokine receptors and contributes to the formation of lymphoid tumors when expressed at high levels. Here we show that the protein kinase Cdc25 C-associated kinase 1 (C-TAK1) is a binding partner and a substrate of Pim-1. A physical interaction of Pim-1 and C-TAK1 could be shown biochemically and in yeast two-hybrid assays. Immunofluorescence experiments suggested that Pim-1.C-TAK1 complexes are predominantly cytoplasmic. When transiently transfected, Pim-1 was also found in the nucleus and could recruit C-TAK1 to this compartment. Both Pim-1 and C-TAK1 underwent autophosphorylation, but only Pim-1 was able to phosphorylate C-TAK1 but not vice versa. Mass spectrometry analysis of C-TAK1 suggested that the sites of autophosphorylation and Pim-1-mediated phosphorylation are distinct and not overlapping. Phosphorylation by Pim-1 decreased C-TAK1 kinase activity significantly, in particular its ability to phosphorylate and inactivate Cdc25C, a protein that actively promotes cell cycle progression at the G(2)/M phase. Hence our findings directly suggest a novel role for Pim-1 as a positive regulator at the G(2)/M transition of the cell cycle.
Institut für Zellbiologie (Tumorforschung), IFZ, Universitätsklinikum Essen, Virchowstrasse 173, D-45122 Essen, Germany.
Malte
M
Bachmann
Hanjo
H
Hennemann
Pei Xiang
PX
Xing
Ingrid
I
Hoffmann
Tarik
T
Möröy
D000818:Animals; D002453:Cell Cycle / Q000502:physiology*; D002460:Cell Line; D006801:Humans; D051379:Mice; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D051573:Proto-Oncogene Proteins c-pim-1; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D020798:Two-Hybrid System Techniques
D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; C111833:MARK3 protein, human; C496634:PIM1 protein, human; C496636:Pim1 protein, mouse; C496637:Pim1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051573:Proto-Oncogene Proteins c-pim-1