Direct transcriptional activation of human caspase-1 by tumor suppressor p⁵³

Abstract

The tumor suppressor protein p⁵³ is a sequence-specific DNA-binding protein, and its biological responses are very often mediated by transcriptional activation of various target genes. Here we show that caspase-1 (interleukin-1β converting enzyme), which plays a role in the production of proinflammatory cytokines and in apoptosis, is a transcriptional target of p⁵³. Caspase-1 mRNA levels increased upon overexpression of p⁵³ by transfection in MCF-7 cells. Human caspase-1 promoter showed a sequence homologous to the consensus p⁵³-binding site. This sequence bound to p⁵³ in gel shift assays. A caspase-1 promoter-reporter construct was activated 6-8-fold by cotransfection with normal p⁵³ but not by mutant p⁵³ (His²⁷³) in HeLa, as well as MCF-7, cells. Mutation of the p⁵³-binding site in caspase-1 promoter abolished transactivation by p⁵³. Treatment ofp⁵³-positive MCF-7 cells with the DNA-damaging drug, doxorubicin, which increases p⁵³ levels, enhanced caspase-1 promoter activity 4-5-fold, but similar treatment of MCF-7-mp⁵³ (a clone of MCF-7 cells expressing mutantp⁵³) and p⁵³-negative HeLa cells with doxorubicin did not increase caspase-1 promoter activity. Doxorubicin treatment increased caspase-1 mRNA levels in MCF-7 cells but not in MCF-7-mp⁵³ or HeLa cells. These results show that endogenous p⁵³ can regulate caspase-1 gene expression.