1. ¹Burnham Institute for Medical Research, Cancer Research Center, La Jolla, CA 92037, USA
2. ²Sidney Kimmel Cancer Center, San Diego, CA 92121, USA
3. ³Pathology and Laboratory Medicine, University of California at Irvine, Irvine, CA 92697-4800, USA

Correspondence: ED Adamson, The Burnham Institute, 10901 N. Torrey Pines Road, La Jolla, CA 92037, USA. Tel: +1 858 646 3100 X3650; Fax: +1 858 646 3198; E-mail: eadamson@burnham.org

Received 16 February 2006; Revised 10 July 2006; Accepted 11 July 2006; Published online 22 September 2006.

Abstract

p73, a transcription factor rarely mutated in cancer, regulates a subset of p53 target genes that cause cells to respond to genotoxic stress by growth arrest and apoptosis. p73 is produced in two main forms; only TAp73 reiterates the roles of p53, while Np73 can be oncogenic in character. We show that the TAp73 form produced by TP73 P1 promoter has five distinct Egr1-binding sites, each contributing to the transcriptional upregulation of TAp73 by Egr1 in several cell types. In contrast, TP73 P2 promoter transcribes Np73, is not induced by Egr1, but is induced by TAp73 and p53. Induction of TAp73 by genotoxic stress requires Egr1 in mouse in vivo. Newly discovered non-consensus p53-binding sites in p73, p53 and Egr1 promoters reveal inter-regulating networks and sustained expression by feedback loops in response to stress, resulting in prolonged expression of the p53 family of genes and efficient apoptosis.