c-Rel Arrests the Proliferation of HeLa Cells and Affects Critical Regulators of the G1/S-Phase Transition

A tetracycline-regulated system was used to characterize the effects of c-Rel on cell proliferation. The expression of c-Rel in HeLa cells led to growth arrest at the G1/S-phase transition, which correlated with its nuclear localization and the induction of endogenous IkappaB alpha expression. These changes were accompanied by a decrease in E2F DNA binding and the accumulation of the hypophosphorylated form of Rb. In vitro kinase assays showed a reduction in Cdk2 kinase activity that correlated with elevated levels of p21WAF1 Cdk inhibitor and p53 tumor suppressor protein. While the steady-state levels of WAF1 transcripts were increased, pulse-chase analysis revealed a sharp increase in p53 protein stability. Importantly, the deletion of the C-terminal transactivation domains of c-Rel abolished these effects. Together, these studies demonstrate that c-Rel can affect cell cycle control and suggest the involvement of the p21WAF1 and p53 cell cycle regulators.