7-Hydroxystaurosporine (UCN-01) causes redistribution of proliferating cell nuclear antigen and abrogates cisplatin-induced S-phase arrest in Chinese hamster ovary cells.
A variety of agents, such as caffeine, have been shown to abrogate the DNA damage-dependent G2 checkpoint and enhance cytotoxicity. However, these agents are too toxic for clinical use. We have reported that the potent protein kinase inhibitor 7-hydroxystaurosporine (UCN-01) at nontoxic doses abrogates the G2 arrest caused by the DNA-damaging agent cisplatin. Here, using Chinese hamster ovary cells, we show that cisplatin causes predominantly an S-phase arrest; UCN-01 abrogates this S-phase arrest, causing progression of cells to G2 and, subsequently, apoptotic cell death. In searching for an explanation for this accelerate DNA synthesis, we discovered that UCN-01 caused translocation of proliferating cell nuclear antigen (PCNA) to the detergent-insoluble, DNA-bound fraction. PCNA acts as a sliding clamp for DNA polymerase delta. Sequestering of PCNA by p21waf1/cip1 is required for p53-dependent G1 arrest in damaged cells. However, the S-phase arrest occurs independently of p53 and p21waf1/cip1. Our results suggest that PCNA is also a component of this S-phase checkpoint, despite the fact that CHO cells are defective for p53, and no increase in p21waf1/cip1 was observed. The mechanism by which PCNA is sequestered in the absence of p21waf1/cip1 and the mechanism by which UCN-01 disrupts this sequestration remain to be elucidated.
Bunch
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RT
Department of Pharmacology and Toxicology, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
Eastman
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D000470:Alkaloids / Q000494:pharmacology*; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D016590:Aphidicolin / Q000494:pharmacology; D016203:CDC2 Protein Kinase / Q000378:metabolism; D016466:CHO Cells; D002458:Cell Fractionation; D002945:Cisplatin / Q000494:pharmacology*; D006224:Cricetinae; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000502:physiology; D004247:DNA / Q000096:biosynthesis; D053938:DNA Fragmentation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016195:G2 Phase / Q000502:physiology; D010766:Phosphorylation; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism*; D047428:Protein Kinase Inhibitors; D016196:S Phase / Q000187:drug effects*; D019311:Staurosporine / Q000031:analogs & derivatives; D016159:Tumor Suppressor Protein p53 / Q000502:physiology
D000470:Alkaloids; D000970:Antineoplastic Agents; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004791:Enzyme Inhibitors; D018809:Proliferating Cell Nuclear Antigen; D047428:Protein Kinase Inhibitors; D016159:Tumor Suppressor Protein p53; D016590:Aphidicolin; C054852:7-hydroxystaurosporine; D004247:DNA; D016203:CDC2 Protein Kinase; D019311:Staurosporine; D002945:Cisplatin