Mutant p53 rescues human diploid cells from senescence without inhibiting the induction of SDI1/WAF1
Bond, J.A.; Blaydes, J.P.; Rowson, J.; Haughton, M.F.; Smith, J.R.; Wynford-Thomas, D.; Wyllie, F.S.
Cancer Research 55(11): 2404-2409
1995
ISSN/ISBN: 0008-5472 PMID: 7538902 Document Number: 453498
Although the cyclin-dependent kinase inhibitor p21-SD11 (WAF1/CIP1) has been proposed as the mediator of p53-induced cell cycle arrest following DNA damage, several stimuli now appear to induce SDI1 independent of p53 function. We have examined the behavior of p53 and SDI1 in an isogeneic model by manipulating p53 status in normal diploid human fibroblasts using an amphotropic retroviral vector. Following DNA strand break damage induced by bleomycin, both SDI1 induction and G-1-S cell cycle arrest are p53 dependent, consistent with SDI1 being the key mediator. In contrast, in cellular senescence (and following UV irradiation), induction of SDI1 occurs independent of p53 function vet growth arrest is still p53 dependent. We conclude (a) that redundant pathways exist for induction of SDI1, but that (b) SDI1, while perhaps necessary, is not sufficient for inhibition of cell cycle progression, requiring the cooperation of an additional factor (possibly another cyclin-dependent kinase inhibitor) whose expression, at least in the case of senescence, is strictly p53 dependent.