[The lack of G1/S arrest of teratocarcinoma F9 cells is determinated by degradation of cyclin-dependent kinases inhibitor p21waf1/cip1].
We have studied the ability of F9 teratocarcinoma cells to arrest in G1/S and G2/M checkpoints following gamma-irradiation. Wild-type p53 protein is rapidly accumulated in F9 cells after gamma-irradiation, however this is not followed by G1/S arrest; there is just a reversible delay of the cell cycle in G2/M. In order to elucidate the reasons of the lack of G1/S arrest in F9 cells we investigated the levels of regulatory cell cycle proteins: G1-cyclins, cyclin dependent kinases and kinase inhibitor p21WAF1/CIP1. We have shown that in spite of p53-dependent activation of p21WAF1/CIP1 promoter, p21WAF1/CIP1 protein is not revealed by different polyclonal and monoclonal antibodies, either by immunoblotting or by immunofluorescent staining. However, when cells are treated with specific proteasome inhibitor lactacystin, p21WAF1/CIP1 protein is revealed. We therefore suggest that p21WAF1/CIP1 protein is subjected to proteasome degradation in F9 cells and probably the lack of G1/S arrest after gamma-irradiation is due to this degradation. Thus, it is the combination of functionally active p53 with low level expression of p21WAF1/CIP1 that causes a short delay of the cell cycle progression in G2/M, rather than the G1-arrest after gamma-irradiation of F9 cells.
Malashicheva
A B
AB
Institute of Cytology, Russian Academy of Sciences, St. Petersburg.
Kisliakova
T V
TV
Pospelov
V A
VA
D000818:Animals; D002471:Cell Transformation, Neoplastic; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D016213:Cyclins / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000378:metabolism*; D016193:G1 Phase; D051379:Mice; D016196:S Phase; D015398:Signal Transduction; D018243:Teratocarcinoma / Q000378:metabolism* / Q000473:pathology*; D014407:Tumor Cells, Cultured
C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004791:Enzyme Inhibitors; D018844:Cyclin-Dependent Kinases