Activation of cyclin A-dependent kinases associated with WAF1 degradation during radiation-induced apoptosis

Abstract

We describe here the further characterisation of the radiation response of a pair of isogenic Burkitt's lymphoma cell lines which differ significantly in their susceptibility to radiation-induced apoptosis. In both cases a marked inhibition of cyclin A-dependent kinase activity was observed at 4 h post-irradiation which recovered to normal levels in the susceptible line by 12 h but remained inhibited in the resistant cell line. Under these conditions the cellular abundance of p58 cyclinA and p33 cdk2 did not significantly change in the two cell types and there was no evidence for phosphorylation changes in p33 cdk2 which might account for the activity differences. In parallel with the changes in activity, p21 WAF1 increased initially in both cell lines, declined in the sensitive cell line as the activity recovered but remained high in the resistant cell line. This appears to be explained by a more rapid turn-over of p21 WAF1 in the sensitive cell line and an increased association of p21 WAF1 with cyclin kinase as determined by immunoprecipitation. These results implicate p21 WAF1 in the regulation of cyclindependent kinases during radiation-induced apoptosis, with persistence of induced p21 WAF1 being associated with a more resistant phenotype.

A link between cell cycle and cell death: Bax and Bcl-2 modulate Cdk2 activation during thymocyte apoptosis

“…The cdks in turn are positively regulated by association with cyclins and are required for cell‐cycle progression (Norbury and Nurse, 1992; Morgan, 1995; Elledge et al ., 1996). Several reports have shown the activation of various Cdks to correlate with apoptosis (Meikrantz et al ., 1994; Shi et al ., 1994; Li et al ., 1995; Wei et al ., 1997; Zhang et al ., 1997; Levkau et al ., 1998). It has been shown that dominant negative alleles of Cdk2 can alleviate tumour necrosis factor‐α (TNFα)‐ and staurosporine‐induced apoptosis in HeLa cells (Meikrantz and Schlegel, 1996) and more recently, apoptosis induced by growth factor withdrawal from human umbilical vein endothelial cells (Levkau et al ., 1998).…”

“…Independent single-cell derived BaF3 clones with similar expression levels of the transfected Cdk2 protein behaved similarly to the clone shown (data not shown). Wei et al, 1997;Zhang et al, 1997;Levkau et al, 1998). It has been shown that dominant negative alleles of Cdk2 can alleviate tumour necrosis factor-α (TNFα)-and staurosporine-induced apoptosis in HeLa cells (Meikrantz and Schlegel, 1996) and more recently, apoptosis induced by growth factor withdrawal from human umbilical vein endothelial cells (Levkau et al, 1998).…”