Transcription Factor NF-κB Differentially Regulates Death Receptor 5 Expression Involving Histone Deacetylase 1

Abstract

The transcription factor nuclear factor κB (NF-κB) regulates the expression of both antiapoptotic and proapoptotic genes. Death receptor 5 (DR5, TRAIL-R2) is a proapoptotic protein considered to be a potential target for cancer therapy, and its expression is mediated by NF-κB. The mechanism of NF-κB-induced DR5 expression is, however, unknown. Herein, we determined that etoposide-induced DR5 expression requires the first intronic region of the DR5 gene. Mutation of a putative NF-κB binding site in this intron eliminates DR5 promoter activity, as do mutations in the p53 binding site in this region. Reduction in p53 expression also blocks p65 binding to the intronic region of the DR5 gene, indicating cooperation between p53 and p65 in DR5 expression. In contrast, the antiapoptotic stimulus, epidermal growth factor (EGF), fails to increase DR5 expression but effectively activates NF-κB and induces p65 binding to the DR5 gene. EGF, however, induces the association of histone deacetylase 1 (HDAC1) with the DR5 gene, whereas etoposide treatment fails to induce this association. Indeed, HDAC inhibitors activate NF-κB and p53 and upregulate DR5 expression. Blockage of DR5 activation decreased HDAC inhibitor-induced apoptosis, and a combination of HDAC inhibitors and TRAIL increased apoptosis. This provides a mechanism for regulating NF-κB-mediated DR5 expression and could explain the differential roles NF-κB plays in regulating apoptosis.

ACKNOWLEDGMENTS

We thank T. Sakai, A. Hoffmans, and D. Baltimore for kind gift of reagents.

S. Shetty was supported by a fellowship from the CancerCare Manitoba Foundation. This research was supported by Leukemia and Lymphoma Society and the Manitoba Health Research Council grants. S. Gibson is supported by a new investigator award from the Canadian Institutes of Health Research.