title: Electron trap for DNA-bound repair enzymes: a strategy for DNA-mediated signaling.
abstract: Despite a low copy number within the cell, base excision repair (BER) enzymes readily detect DNA base lesions and mismatches. These enzymes also contain [Fe4S4] clusters, yet a redox role for these iron cofactors had been unclear. Here, we provide evidence that BER proteins may use DNA-mediated redox chemistry as part of a signaling mechanism to detect base lesions. By using chemically modified bases, we show electron trapping on DNA in solution with bound BER enzymes by electron paramagnetic resonance (EPR) spectroscopy. We demonstrate electron transfer from two BER proteins, Endonuclease III (EndoIII) and MutY, to modified bases in DNA containing oxidized nitroxyl radical EPR probes. Electron trapping requires that the modified base is coupled to the DNA pi-stack, and trapping efficiency is increased when a noncleavable MutY substrate analogue is located distally to the trap. These results are consistent with DNA binding leading to the activation of the repair proteins toward oxidation. Significantly, these results support a mechanism for DNA repair that involves DNA-mediated charge transport.
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
authors.forename: Eylon
authors.initials: E
authors.lastname: Yavin
authors.forename: Eric D A
authors.initials: ED
authors.lastname: Stemp
authors.forename: Valerie L
authors.initials: VL
authors.lastname: O'shea
authors.forename: Sheila S
authors.initials: SS
authors.lastname: David
authors.forename: Jacqueline K
authors.initials: JK
authors.lastname: Barton
mesh_terms: D001483:Base Sequence; D045647:DNA Glycosylases / Q000378:metabolism; D004260:DNA Repair; D045643:DNA Repair Enzymes / Q000378:metabolism*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D043224:Deoxyribonuclease (Pyrimidine Dimer) / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D004579:Electron Transport; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism; D008954:Models, Biological; D015398:Signal Transduction; D013113:Spin Labels
chemical_list: D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D013113:Spin Labels; D043224:Deoxyribonuclease (Pyrimidine Dimer); C106403:NTH protein, E coli; D045647:DNA Glycosylases; C061738:mutY adenine glycosylase; D045643:DNA Repair Enzymes