Rum1, an inhibitor of cyclin-dependent kinase in fission yeast, is negatively regulated by mitogen-activated protein kinase-mediated phosphorylation at Ser and Thr residues.
The p25(rum1) is an inhibitor of Cdc2 kinase expressed in fission yeast and plays an important role in cell-cycle control. As its amino-acid sequence suggests that p25(rum1) has putative phosphorylation sites for mitogen-activated protein kinase (MAPK), we investigated the ability of MAPK to phosphorylate p25(rum1). Direct in vitro kinase assay using GST-fusion proteins of wild-type as well as various mutants of p25(rum1) demonstrated that MAPK phosphorylates the N-terminal portion of p25(rum1) and residues Thr13 and Ser19 are major phosphorylation sites for MAPK. In addition, phosphorylation of p25(rum1) by MAPK revealed markedly reduced Cdc2 kinase inhibitor ability of the protein. Together with the fact that replacement of both Thr13 and Ser19 with Glu, which mimics the phosphorylated state of these residues, also significantly reduces the activity of p25(rum1) as a Cdc2 inhibitor, it was suggested that the phosphorylation of Thr13 and Ser19 negatively regulates the function of p25(rum1). Further evidence indicates that phosphorylation of Thr13 and Ser19 may retain a negative effect on the function of p25(rum1) even in vivo. Therefore, MAPK may regulate the function of p25(rum1) via phosphorylation of its Thr and Ser residues and thus participate in cell cycle control in fission yeast.
Department of Pathology, National Children's Medical Research Center, Tokyo, Japan.
Kentaro
K
Matsuoka
Nobutaka
N
Kiyokawa
Tomoko
T
Taguchi
Jun
J
Matsui
Toyo
T
Suzuki
Kenichi
K
Mimori
Hideki
H
Nakajima
Hisami
H
Takenouchi
Tang
T
Weiran
Yohko U
YU
Katagiri
Junichiro
J
Fujimoto
D019943:Amino Acid Substitution; D000818:Animals; D016203:CDC2 Protein Kinase / Q000037:antagonists & inhibitors; D002453:Cell Cycle; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010766:Phosphorylation; D010768:Phosphoserine / Q000737:chemistry; D010769:Phosphothreonine / Q000737:chemistry; D011499:Protein Processing, Post-Translational; D012568:Schizosaccharomyces / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013215:Starfish
C086077:Rum1 protein, S pombe; D029702:Schizosaccharomyces pombe Proteins; D010769:Phosphothreonine; D010768:Phosphoserine; D016203:CDC2 Protein Kinase; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases