Roscovitine (CYC202)

Kinases activities are assayed at 30 °C in buffer C. Blank values are subtracted from the data and activities calculated as molar amount of phosphate incorporated in protein acceptor during a 10-minute incubation. Controls are performed with appropriate dilutions of DMSO. In a few cases, phosphorylation of the substrate is assessed by autoradiography after SDS/PAGE. p34^cdc2/cyclin B is purified from M-phase starfish (M. glacialis) oocytes by affinity chromatography. It is assayed with 1 mg histone Hl/mL, in the presence of 15 μM [γ-³²P]ATP (3000 Ci/mmol; 1 mCi/mL) in a final volume of 30 μL. After a 10-minute incubation at 30 °C, 25-μL aliquots of supernatant are spotted onto pieces of Whatman P81 phosphocellulose paper, and, after 20 seconds, the filters are washed five times (for at least 5 minutes each time) in a solution of 10mL phosphoric acid/L water. The wet filters are transferred into 6-mL plastic scintillation vials, 5 mL ACS scintillation fluid is added and the radioactivity measured in a Packard counter. The kinase activity is expressed as molar amount of phosphate incorporated in histone H1 during a 10-minutes incubation or as a percentage of maximal activity. p33^cdk2/cyclin A and p33^cdk2/cyclinE are reconstituted from extracts of sf9 insect cells infected with various baculoviruses. Cyclins A and E are fusion proteins with glutathione S-transferase and the complexes are purified on glutathione-agarose beads. Kinase activities are assayed with 1 mg/mL histone H1, in the presence of 15 μM [γ-³²P]ATP, during 10 minutes, in a final volume of 30 μL, as described for the p34^cdc2/cyclin B kinase. p33^cdk5/p35 is purified from bovine brain, excluding the Mono S-chromatographic step. The active fractions from the Superose 12 column are pooled and concentrated to a final concentration of approximately 25 μg enzyme/mL. The kinase is assayed with 1 mg/mL histone HI in the presence of 15 μM [γ-³²P]ATP, during 10 minutes in a final volume of 30 μL, as described for the p34^cdc2/cyclin B kinase. p33^cdk5/cyclin D1 is obtained from insect cell lysates. Cdk4 is a fusion protein with glutathione-S-transferase and the active complex is purified on glutathione-agarose beads. Its kinase activity is assayed with purified retinoblastoma protein (complexed with glutathione-S-transferase) in the presence of 15 μM [γ-³²P]ATP, in a final volume of 30 μL. After a 15-minute incubation, 30 μL Laemmli sample buffer is added. The phosphorylated substrate is resolved by 10 % SDS/PAGE and analysed by autoradiography by overnight exposure to Hyperfilm MP and densitometry. p33^cdk4/cyclinD 2 is obtained from insect cell lysates. It is assayed with purified retinoblastoma protein (complexed with glutathione-S-transferase) in the presence of 15 μM [γ-³²P]ATP in a final volume of 30 μL. After a 30-minute incubation, 30 μL Laemmli sample buffer is added. The phosphorylated substrate is resolved by 10% SDS/PAGE and analysed by autoradiography by overnight exposure to Hyperfilm MP and densitometry. MAP kinase erkl (tagged with glutathione-S-transferase), is expressed in bacteria, purified on glutathione-agarose beads and assayed with 1 mg myelin basic protein/ml in the presence of 15 μM [γ-³²P]ATP as described above for the p34^cdc2cyclin B kinase. His-tagged erkl and erk2 are activated in vitro by mitogen-activated protein kinase kinase, purified (Ni-affinity and Mono Q) and assayed as described above during 10 minutes in a final volume of 30 μL. Protein kinase C isoforms are purified from baculovirus infected sf9 insect cells and assayed with 1 mg/mL protamine sulfate in the presence of 15 μM [γ-³²P]ATP, during 10 minutes at 30 °C, in a final volume of 30 μL. Phosphorylated protamine sulfate is recovered on Whatman P81 phosphocellulose paper as described for the cdc2 kinase. The catalytic subunit of cAMP-dependent protein kinase, purified from bovine heart, is assayed with 1 mg histone Hl/ml, in the presence of 15 μM [γ-³²P]ATP as described for the p34^cdc2/cyclin B kinase. cGMP-dependent protein kinase, purified to homogeneity from bovine tracheal smooth muscle, is assayed with 1 mg histone Hl/mL, in the presence of 15 μM [γ-³²P]ATP as described for the p34^cdc2/cyclin B kinase. Casein kinase 2 is isolated from rat liver cytosol and assayed with 1 mg casein/mL and 15 μM [γ-³²P]ATP. The substrate is spotted on Whatmann 3MM filters and washed with 10% (mass/vol.) trichloroacetic acid. Myosin light chain kinase, purified from chicken gizzard is assayed in the presence of 100 nM calmodulin, 100 μM CaCl₂, 50 mM Hepes, 5 mM MgCI,, 1 mM dithiothreitol and 0.1 mg BSA/ml at pH 7.5 using a synthetic peptide based on the smooth-muscle myosin light-chain phosphorylation site and in the presence of 15 μM [γ-³²P]ATP, in a final volume of 50 μL. Incorporation of radioactive phosphate is monitored on phosphocellulose filters as described above. ASK-γ, a plant homologue of GSK-3, is expressed as a glutathione-S-transferase fusion protein in Escherichia coli and purified on glutathione-agarose. ASK-γ kinase is assayed, for 10 minutes at 30 °C, with 5 μg myelin basic protein, in the presence of 15 μM [γ-³²P]ATP in a final volume of 30 μL. The phosphorylated myelin basic protein is recovered on Whatman P81 phosphocellulose paper as described for the p34^cdc2/cyclin B kinase. Insulin receptor tyrosine kinase domain (CIRK-41) is overexpressed in a baculovirus system and purified to homogeneity. Its kinase activity is assayed, for 10 minutes at 30 °C, with 5 μg Raytide, in the presence of 15 μM [γ-³²P]ATP, in a final volume of 30 μL. The phosphorylated Raytide is recovered on Whatman P81 phosphocellulose paper as described for the p34^cdc2/cyclin B kinase. c-src kinase is purified from infected Sf9 cells. The v-abl kinase is expressed in E. coli and affinity purified on IgG Affigel 10. Both kinases are assayed for 10 minutes at 30 °C, with 5 μg Raytide, in the presence of 15 μM [γ-³²P]ATP, in a final volume of 30 μL. The phosphorylated Raytide is recovered on Whatman P81 phosphocellulose paper as described for the p34^cdc2/cyclin B kinase.