Mutant p53-induced up-regulation of mitogen-activated protein kinase kinase 3 contributes to gain of function.

Mitogen-activated protein kinase kinase 3 (MAP2K3) is a member of the dual specificity kinase group. Growing evidence links MAP2K3 to invasion and tumor progression. Here, we identify MAP2K3 as a transcriptional target of endogenous gain-of-function p53 mutants R273H, R175H, and R280K. We show that MAP2K3 modulation occurred at the mRNA and protein levels and that endogenous mutant p53 proteins are capable of binding to and activate the MAP2K3 promoter. In addition, we found that the studied p53 mutants regulate MAP2K3 gene expression through the involvement of the transcriptional cofactors NF-Y and NF-kappaB. Finally, functional studies showed that endogenous MAP2K3 knockdown inhibits proliferation and survival of human tumor cells, whereas the ectopic expression of MAP2K3 can rescue the proliferative defect induced by mutant p53 knockdown. Taken together, our findings define a novel player through which mutant p53 exerts its gain-of-function activity in cancer cells.