p21WAF1 is dynamically associated with JNK in human T-lymphocytes during cell cycle progression.

We have examined the regulation of the c-Jun NH2-terminal kinase (JNK) subfamily of mitogen-activated protein kinases (MAPKs) in response to inhibition of DNA replication during the cell cycle of human T-lymphocytes. In this study, we demonstrate that JNK is rapidly activated following release of T-lymphocytes from G1/S-phase arrest and that this activation precedes resumption of DNA synthesis upon S-phase progression. We also show that activation of JNK correlates with dissociation of the cyclin-dependent protein kinase (CDK) inhibitor, p21WAF1, from JNK1. Since JNK1 isolated from T-lymphocytes by immunoprecipitation can be inhibited by recombinant p21WAF1 in vitro, these data suggest that JNK activation may be regulated in part by its dissociation from p21WAF1. The observation of a dynamic, physical association of native JNK1 and p21WAF1 in vivo has not previously been described and suggests a novel mechanism for JNK-mediated regulation of the cell cycle of human T-lymphocytes.