Authors: Timo Quante, Benjamin Otto, Marie Brázdová, Iva Kejnovská, Wolfgang Deppert and Genrich V. Tolstonog

Timo Quante

Heinrich-Pette Institute; Leibniz Institute for Experimental Virology; Hamburg, Germany

Benjamin Otto

Institute for Clinical Chemistry – Central Laboratories; Center for Clinical-Theoretical Medicine; University Clinics Eppendorf; Hamburg, Germany

Marie Brázdová

Department of Biophysical Chemistry and Molecular Oncology; Institute of Biophysics AVČR v.v.i.; Brno, Czech Republic

Iva Kejnovská

Department of Biophysical Chemistry and Molecular Oncology; Institute of Biophysics AVČR v.v.i.; Brno, Czech Republic; CEITEC – Central European Institute of Technology; Masaryk University; Brno, Czech Republic

Wolfgang Deppert

Corresponding author: wolfgang.deppert@hpi.uni-hamburg.de
Heinrich-Pette Institute; Leibniz Institute for Experimental Virology; Hamburg, Germany
Current affiliation: Institute for Tumor Biology; University Medical Center Hamburg-Eppendorf; Hamburg, Germany

Genrich V. Tolstonog

Corresponding author: genrich.tolstonog@hpi.uni-hamburg.de
Heinrich-Pette Institute; Leibniz Institute for Experimental Virology; Hamburg, Germany
Current affiliation: Department of Otolaryngology and Head and Neck Surgery, University Hospital CHUV, Lausanne, Switzerland

Abstract:
The molecular mechanisms underlying mutant p53 (mutp53) “gain-of-function” (GOF) are still insufficiently understood, but there is evidence that mutp53 is a transcriptional regulator that is recruited by specialized transcription factors. Here we analyzed the binding sites of mutp53 and the epigenetic status of mutp53-regulated genes that had been identified by global expression profiling upon depletion of endogenous mutp53 (R273H) expression in U251 glioblastoma cells. We found that mutp53 preferentially and autonomously binds to G/C-rich DNA around transcription start sites (TSS) of many genes characterized by active chromatin marks (H3K4me3) and frequently associated with transcription-competent RNA polymerase II. Mutp53-bound regions overlap predominantly with CpG islands and are enriched in G4-motifs that are prone to form G-quadruplex structures. In line, mutp53 binds and stabilizes a well-characterized G-quadruplex structure in vitro. Hence, we assume that binding of mutp53 to G/C-rich DNA regions associated with a large set of cancer-relevant genes is an initial step in their regulation by mutp53. Using GAS1 and HTR2A as model genes, we show that mutp53 affects several parameters of active transcription. Finally, we discuss a dual mode model of mutp53 GOF, which includes both stochastic and deterministic components.

Received: July 25, 2012; Accepted: July 26, 2012; Published Online: August 21, 2012

Preview: