The cyclin H/cdk7/Mat1 kinase activity is regulated by CK2 phosphorylation of cyclin H.
Cyclin dependent kinases are regulated by phosphorylation and dephosphorylation of the catalytic cdk subunits, by assembly with specific cyclins and by specific inhibitor molecules. Recently, it turned out that cyclins are also phosphoproteins, which means that they are also potential targets for a regulation by phosphorylation and dephosphorylation. Here, we show that cyclin H was phosphorylated by protein kinase CK2. Like most other CK2 substrates cyclin H was much better phosphorylated by the CK2 holoenzyme than by the alpha-subunit alone. By using point mutants derived from the cyclin H sequence we mapped the CK2 phosphorylation site at threonine 315 at the C-terminal end of cyclin H. Phosphorylation at this position had no influence on the assembly of the cyclin H/cdk7/Mat1 complex. However, phosphorylation at amino acid 315 of cyclin H turned out to be critical for a full cyclin H/cdk7/Mat1 kinase activity when the CTD peptide of RNA polymerase II or cdk2 was used as a substrate.
Medical Biochemistry and Molecular Biology, University of the Saarland, Building 44, D-66424, Homburg, Germany.
Eberhard
E
Schneider
Sabine
S
Kartarius
Norbert
N
Schuster
Mathias
M
Montenarh
D000595:Amino Acid Sequence; D001665:Binding Sites; D015153:Blotting, Western; D047390:Casein Kinase II; D002460:Cell Line; D056748:Cyclin H; D018844:Cyclin-Dependent Kinases; D016213:Cyclins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D006367:HeLa Cells; D020035:Holoenzymes / Q000378:metabolism; D006801:Humans; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D000095043:Cyclin-Dependent Kinase-Activating Kinase
C534751:CCNH protein, human; D056748:Cyclin H; D016213:Cyclins; D020035:Holoenzymes; D046911:Macromolecular Substances; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases; D018844:Cyclin-Dependent Kinases; D000095043:Cyclin-Dependent Kinase-Activating Kinase; C000722416:CDK7 protein, human