The Chk1 protein kinase and the Cdc25C regulatory pathways are targets of the anticancer agent UCN-01. Graves, P. R., Yu, L., Schwarz, J. K., Gales, J., Sausville, E. A., O'Connor, P. M., & Piwnica-Worms, H. The Journal of Biological Chemistry, 275(8):5600–5605, February, 2000.
abstract   bibtex   
A checkpoint operating in the G(2) phase of the cell cycle prevents entry into mitosis in the presence of DNA damage. UCN-01, a protein kinase inhibitor currently undergoing clinical trials for cancer treatment, abrogates G(2) checkpoint function and sensitizes p53-defective cancer cells to DNA-damaging agents. In most species, the G(2) checkpoint prevents the Cdc25 phosphatase from removing inhibitory phosphate groups from the mitosis-promoting kinase Cdc2. This is accomplished by maintaining Cdc25 in a phosphorylated form that binds 14-3-3 proteins. The checkpoint kinases, Chk1 and Cds1, are proposed to regulate the interactions between human Cdc25C and 14-3-3 proteins by phosphorylating Cdc25C on serine 216. 14-3-3 proteins, in turn, function to keep Cdc25C out of the nucleus. Here we report that UCN-01 caused loss of both serine 216 phosphorylation and 14-3-3 binding to Cdc25C in DNA-damaged cells. In addition, UCN-01 potently inhibited the ability of Chk1 to phosphorylate Cdc25C in vitro. In contrast, Cds1 was refractory to inhibition by UCN-01 in vitro, and Cds1 was still phosphorylated in irradiated cells treated with UCN-01. Thus, neither Cds1 nor kinases upstream of Cds1, such as ataxia telangiectasia-mutated, are targets of UCN-01 action in vivo. Taken together our results identify the Chk1 kinase and the Cdc25C pathway as potential targets of G(2) checkpoint abrogation by UCN-01.
@article{graves_chk1_2000,
	title = {The {Chk1} protein kinase and the {Cdc25C} regulatory pathways are targets of the anticancer agent {UCN}-01},
	volume = {275},
	issn = {0021-9258},
	abstract = {A checkpoint operating in the G(2) phase of the cell cycle prevents entry into mitosis in the presence of DNA damage. UCN-01, a protein kinase inhibitor currently undergoing clinical trials for cancer treatment, abrogates G(2) checkpoint function and sensitizes p53-defective cancer cells to DNA-damaging agents. In most species, the G(2) checkpoint prevents the Cdc25 phosphatase from removing inhibitory phosphate groups from the mitosis-promoting kinase Cdc2. This is accomplished by maintaining Cdc25 in a phosphorylated form that binds 14-3-3 proteins. The checkpoint kinases, Chk1 and Cds1, are proposed to regulate the interactions between human Cdc25C and 14-3-3 proteins by phosphorylating Cdc25C on serine 216. 14-3-3 proteins, in turn, function to keep Cdc25C out of the nucleus. Here we report that UCN-01 caused loss of both serine 216 phosphorylation and 14-3-3 binding to Cdc25C in DNA-damaged cells. In addition, UCN-01 potently inhibited the ability of Chk1 to phosphorylate Cdc25C in vitro. In contrast, Cds1 was refractory to inhibition by UCN-01 in vitro, and Cds1 was still phosphorylated in irradiated cells treated with UCN-01. Thus, neither Cds1 nor kinases upstream of Cds1, such as ataxia telangiectasia-mutated, are targets of UCN-01 action in vivo. Taken together our results identify the Chk1 kinase and the Cdc25C pathway as potential targets of G(2) checkpoint abrogation by UCN-01.},
	language = {eng},
	number = {8},
	journal = {The Journal of Biological Chemistry},
	author = {Graves, P. R. and Yu, L. and Schwarz, J. K. and Gales, J. and Sausville, E. A. and O'Connor, P. M. and Piwnica-Worms, H.},
	month = feb,
	year = {2000},
	keywords = {Alkaloids, Antineoplastic Agents, Cell Cycle Proteins, Checkpoint Kinase 1, Checkpoint Kinase 2, Cloning, Molecular, DNA Damage, Dose-Response Relationship, Radiation, G2 Phase, HeLa Cells, Humans, Membrane Proteins, Models, Biological, Phosphorylation, Plasmids, Protein Kinase Inhibitors, Protein Kinases, Protein-Serine-Threonine Kinases, Protein-Tyrosine Kinases, Serine, Staurosporine, Time Factors, cdc25 Phosphatases},
	pages = {5600--5605},
}

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