title: A role for DNA-mediated charge transport in regulating p53: Oxidation of the DNA-bound protein from a distance.
abstract: Charge transport (CT) through the DNA base pairs provides a means to promote redox reactions at a remote site and potentially to effect signaling between molecules bound to DNA. Here we describe the oxidation of a cell-cycle regulatory protein, p53, from a distance through DNA-mediated CT. A consensus p53 binding site as well as three DNA promoters regulated by p53 were synthesized containing a tethered DNA photooxidant, anthraquinone. Photoinduced oxidation of the protein occurs from a distance; introduction of an intervening CA mismatch, which inhibits DNA-mediated CT, prevents oxidation of p53. DNA-mediated oxidation is shown to promote dissociation of p53 from only some promoters, and this sequence-selectivity in oxidative dissociation correlates with the biological regulation of p53. Under severe oxidative stress, effected here through oxidation at long range, p53 dissociates from a promoter that activates DNA repair as well as the promoter for the negative regulator of p53, Mdm2, but not from a promoter activating cell-cycle arrest. Mass spectrometry results are consistent with disulfide bond formation in p53 upon DNA-mediated oxidation. Furthermore, DNA-bound p53 oxidation is shown in vivo by up-regulation of p53 and subsequent irradiation in the presence of a rhodium photooxidant to give a new p53 adduct that can be reversed with thiol treatment. This DNA-mediated oxidation of p53 parallels that seen by treating cells with hydrogen peroxide. These results indicate a unique mechanism using DNA-mediated CT chemistry by which p53 activity on different promoters may be controlled globally under conditions of oxidative stress.
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
authors.forename: Katherine E
authors.initials: KE
authors.lastname: Augustyn
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Merino
authors.forename: Jacqueline K
authors.initials: JK
authors.lastname: Barton
mesh_terms: D000880:Anthraquinones / Q000528:radiation effects; D002453:Cell Cycle / Q000235:genetics; D018797:Cell Cycle Proteins / Q000235:genetics; D016384:Consensus Sequence; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics; D003553:Cystine / Q000737:chemistry; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D004260:DNA Repair / Q000235:genetics; D004579:Electron Transport / Q000502:physiology*; D024202:Electrophoretic Mobility Shift Assay; D007364:Intercalating Agents / Q000528:radiation effects; D009687:Nuclear Proteins / Q000235:genetics; D009942:Organometallic Compounds / Q000528:radiation effects; D010083:Oxidants, Photochemical / Q000528:radiation effects; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010777:Photochemistry; D011401:Promoter Regions, Genetic; D011485:Protein Binding / Q000528:radiation effects; D011487:Protein Conformation; D051736:Proto-Oncogene Proteins c-mdm2 / Q000235:genetics; D016159:Tumor Suppressor Protein p53 / Q000737:chemistry / Q000378:metabolism*; D000097642:GADD45 Proteins
chemical_list: D000880:Anthraquinones; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D003553:Cystine; D004247:DNA; D007364:Intercalating Agents; D009687:Nuclear Proteins; D009942:Organometallic Compounds; D010083:Oxidants, Photochemical; D051736:Proto-Oncogene Proteins c-mdm2; D016159:Tumor Suppressor Protein p53; C493956:CDKN1A protein, human; C439070:GADD45A protein, human; D000097642:GADD45 Proteins; C402307:Rh-(phi)2(bpy')