Author(s): Liu X, Yue P, Khuri FR, Sun SY
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Abstract Death receptor 4 (DR4) is one of the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptors and triggers apoptosis on ligation with TRAIL or overexpression. Our previous study demonstrated that DR4 expression could be regulated in a p53-dependent fashion. In the present study, we have demonstrated that DR4 is a p53 target gene and is regulated by p53 through a functional intronic p53 binding site (p53BS) based on the following lines of evidence: (a) the p53BS in the DR4 gene is almost identical to the one found in the first intron of the DR5 gene in terms of their locations and sequences; (b) DR4 p53BS bound to p53 protein in intact cells upon p53 activation as demonstrated by a chromatin immunoprecipitation assay; (c) a luciferase reporter vector carrying the DR4 p53BS upstream of an SV40 promoter exhibited enhanced luciferase activity when transiently cotransfected with a wild-type p53 expression vector in p53-null cell lines or stimulated with DNA-damaging agents in a cell line having wild-type p53; and (d) when the DR4 p53BS, together with its own corresponding promoter region in the same orientation as it sits in its natural genomic locus, was cloned into a basic luciferase vector without a promoter element, its transcriptional activity was strikingly increased by cotransfection of a wild-type p53 expression vector or treatment with DNA-damaging agents. However, wild-type p53 or DNA-damaging agents completely lost their activity to increase transcriptional activity of a reporter construct with deleted DR4 p53BS. Thus, we conclude that p53 directly regulates the expression of the DR4 gene via the novel intronic p53BS.
This article was published in Cancer Res
and referenced in Journal of Cancer Science & Therapy