Selective transcription of p53 target genes by zinc finger-p53 DNA binding domain chimeras

Active p53 stimulates the transcription of a number of key genes, including the pro-apoptotic gene bax, as well as p21, a cell cycle regulator. In this study we constructed novel chimeric zinc finger-p53 DNA binding domain (DBD) transcription factors designed to bind to the promoters of specific p53 regulated genes. In order to selectively increase the expression of Bax, we coupled a pre-selected three-zinc finger (Zif) peptide targeted to a sequence in the bax promoter to a minimal p53 DBD. This chimeric protein could increase reporter gene transcription from a minimal bax promoter (up to 10-fold) but not from a minimal p21 promoter in p53-deficient Saos-2 cells. However, fusion proteins carrying longer p53 DBDs displayed entirely different selectivity and potency. Thus, Zif-p53 DBD chimeras containing Nand C-terminal extensions of the minimal DBD could increase transcription driven by a minimal p21 promoter up to 800-fold. These chimeras preferred the minimal p21 promoter up to 500-fold over the minimal bax promoter. Additionally, endogenous p21 message and protein levels were increased in cells expressing the p21 selective Zif-p53 DBD chimera and expression of the chimeric proteins resulted in partial cell cycle arrest. Cell fractionation experiments indicated that the Zifs enhanced nuclear localization of the Zif-p53 DBD chimera. These studies suggest that it is possible to create chimeric transcription factors able to strongly and selectively activate genes downstream of p53. (C) 2004 Elsevier B.V. All rights reserved.