Caspase 3-mediated cleavage of p21WAF1/CIP1 associated with the cyclin A-cyclin-dependent kinase 2 complex is a prerequisite for apoptosis in SK-HEP-1 cells.
Apoptosis of SK-HEP-1 human hepatoma cells induced by treatment with ginsenoside Rh2 (G-Rh2) is associated with rapid and selective activation of cyclin A-associated cyclin-dependent kinase 2 (Cdk2). Here, we show that in apoptotic cells, the Cdk inhibitory protein p21(WAF1/CIP1), which is associated with the cyclin A-Cdk2 complex, undergoes selective proteolytic cleavage. In contrast, another Cdk inhibitory protein, p27(KIP1), which is associated with cyclin A-Cdk2 and cyclin E-Cdk2 complexes, remained unaltered during apoptosis. Ectopic overexpression of p21(WAF1/CIP1) suppressed apoptosis as well as cyclin A-Cdk2 activity induced by treatment of SK-HEP-1 cells with G-Rh2. The suppressive effects of p21(WAF1/CIP1) were much higher in the cells transfected with p21D112N, an expression vector that encodes a p21(WAF1/CIP1) mutant resistant to caspase 3 cleavage. Overexpression of cyclin A in SK-HEP-1 cells dramatically up-regulated cyclin A-Cdk2 activity and accordingly enhances apoptosis induced by treatment with G-Rh2. These up-regulating effects were blocked by coexpression of a dominant negative allele of cdk2. Furthermore, olomoucine, a specific inhibitor of Cdks, also blocked G-Rh2-induced apoptosis. These data suggest that the induction of apoptosis in human hepatoma cells treated with G-Rh2 occurs by a mechanism that involves the activation of cyclin A-Cdk2 by caspase 3-mediated cleavage of p21(WAF1/CIP1).
Jin
Y H
YH
Research Institute for Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul 151-742, South Korea.
Yoo
K J
KJ
Lee
Y H
YH
Lee
S K
SK
D017209:Apoptosis; D042846:CDC2-CDC28 Kinases; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism*; D018797:Cell Cycle Proteins; D019925:Cyclin A / Q000378:metabolism*; D019927:Cyclin E / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016213:Cyclins / Q000235:genetics / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects; D004789:Enzyme Activation; D036145:Ginsenosides; D006801:Humans; D007701:Kinetin; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009154:Mutation; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011687:Purines / Q000494:pharmacology; D012503:Saponins / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins
C493956:CDKN1A protein, human; D018797:Cell Cycle Proteins; D019925:Cyclin A; D019927:Cyclin E; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D036145:Ginsenosides; D008869:Microtubule-Associated Proteins; D011687:Purines; D012503:Saponins; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; C090046:olomoucine; C055305:ginsenoside Rh2; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D007701:Kinetin