title: Cyclin H is a new binding partner for protein kinase CK2.
abstract: The protein kinase CK2 holoenzyme is composed of two regulatory beta- and two catalytic alpha- or alpha(')-subunits. There is ample evidence for the binding of individual subunits of CK2 to various cellular proteins and, moreover, for functions of the individual subunits, which are different from their roles in the holoenzyme. Here, we report that the regulatory cyclin H subunit of the cyclin H/cdk7/Mat1 complex was associated with a protein kinase activity, which shows some similarity with protein kinase CK2. Coimmunoprecipitation experiments supported the existence of complexes of cyclin H and CK2 in mammalian cells. Far Western blot experiments revealed that cyclin H bound to the alpha-subunit but not the alpha(')- and beta-subunits of CK2. Immunofluorescence analysis showed that cyclin H and CK2alpha were colocated in the nucleus. Although cyclin H functions as the regulatory subunit for the cyclin H/cdk7/Mat1 complex, it could not substitute the regulatory beta-subunit of CK2 in its regulatory function of the CK2 activity.
authors.affiliation: Medical Biochemistry and Molecular Biology, University of the Saarland, Building 44, D-66424, Homburg/Saar, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Faust
authors.forename: Sabine
authors.initials: S
authors.lastname: Kartarius
authors.forename: Sandra L
authors.initials: SL
authors.lastname: Schwindling
authors.forename: Mathias
authors.initials: M
authors.lastname: Montenarh
mesh_terms: D000818:Animals; D015153:Blotting, Western; D019556:COS Cells; D047390:Casein Kinase II; D056748:Cyclin H; D016213:Cyclins / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D005455:Fluorescent Antibody Technique; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D056748:Cyclin H; D016213:Cyclins; D011994:Recombinant Proteins; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases