Protein kinase CK1delta phosphorylates key sites in the acidic domain of murine double-minute clone 2 protein (MDM2) that regulate p53 turnover.
Murine double-minute clone 2 protein (MDM2) is an E3 ubiquitin ligase that regulates the turnover of several cellular factors including the p53 tumor suppressor protein. As part of the mechanism of p53 induction in response to DNA damage, a cluster of serine residues within the central acidic domain of MDM2 become hypophosphorylated, leading to attenuation of MDM2-mediated p53 destruction. In the present study, we identify the protein kinase CK1delta as a major cellular activity that phosphorylates MDM2. Amino acid substitution, coupled with phosphopeptide analyses, indicates that several serine residues in the acidic domain, including Ser-240, Ser-242, and Ser-246, as well as Ser-383 in the C-terminal region, are phosphorylated by CK1delta in vitro. We also show, through expression of a dominant negative mutant of CK1delta or treatment of cells with IC261, a CK1delta-selective inhibitor, that MDM2 is phosphorylated by CK1delta in cultured cells. These data establish the identity of a key signaling molecule that promotes the phosphorylation of a major regulatory region in MDM2 under normal growth conditions.
Winter
Markus
M
Institute for Toxicology and Genetics, Forschungszentrum Karlsruhe, PO Box 3640, 76021 Karlsruhe, Germany.
Milne
Diane
D
Dias
Sylvia
S
Kulikov
Roman
R
Knippschild
Uwe
U
Blattner
Christine
C
Meek
David
D
D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D048148:Casein Kinase Idelta / Q000378:metabolism*; D002522:Chlorocebus aethiops; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism*; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051736:Proto-Oncogene Proteins c-mdm2; D012694:Serine / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D016159:Tumor Suppressor Protein p53; D012694:Serine; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; D048148:Casein Kinase Idelta