The kinase inhibitor staurosporine induces G1 arrest at two points: effect on retinoblastoma protein phosphorylation and cyclin-dependent kinase 2 in normal and transformed cells.
Staurosporine (ST), a protein kinase inhibitor, at a concentration of 20 nM arrests normal diploid fibroblasts 3 h into G1 (H. A. Crissman et al., Proc. Natl. Acad. Sci. USA, 88: 7580-7584, 1991; K. Abe et al., Exp. Cell Res., 192: 122-127, 1991). ST (2 nM) induces a new G1 arrest point at 6 h into G1. Partial phosphorylation of the retinoblastoma protein was observed at the 2 nM ST arrest point, whereas the retinoblastoma protein was unphosphorylated or underphosphorylated at the 20 nM arrest point. This correlated with the activity of the cyclin-dependent kinase 2 (CDK2) and the phosphorylation of the Thr160 residue of p33CDK2. The cyclin E and cyclin D1/2 levels were reduced at the 20 nM ST arrest point. In HeLa cells that do not arrest in G1 in response to 2 or 20 nM ST, the retinoblastoma protein and CDK2 phosphorylations and CDK2 activity were not affected by ST. These results suggest that ST inhibits one or more G1-regulating protein kinases, which lie upstream of CDK2.
Department of Biological Chemistry, Medical School, University of California Davis 95616.
J B
JB
Schnier
D M
DM
Gadbois
K
K
Nishi
E M
EM
Bradbury
D000470:Alkaloids / Q000494:pharmacology*; D042846:CDC2-CDC28 Kinases; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D016213:Cyclins / Q000378:metabolism; D005347:Fibroblasts; D016193:G1 Phase / Q000187:drug effects*; D006367:HeLa Cells; D006801:Humans; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D016160:Retinoblastoma Protein / Q000378:metabolism*; D019311:Staurosporine; D013997:Time Factors
D000470:Alkaloids; D016213:Cyclins; D016160:Retinoblastoma Protein; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D019311:Staurosporine