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Protein-DNA charge transport: Redox activation of a DNA repair protein by guanine radical

Yavin, Eylon and Boal, Amie K. and Stemp, Eric D. A. and Boon, Elizabeth M. and Livingston, Alison L. and O'Shea, Valerie L. and David, Sheila S. and Barton, Jacqueline K. (2005) Protein-DNA charge transport: Redox activation of a DNA repair protein by guanine radical. Proceedings of the National Academy of Sciences of the United States of America, 102 (10). pp. 3546-3551. ISSN 0027-8424.

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DNA charge transport (CT) chemistry provides a route to carry out oxidative DNA damage from a distance in a reaction that is sensitive to DNA mismatches and lesions. Here, DNA-mediated CT also leads to oxidation of a DNA-bound base excision repair enzyme, MutY. DNA-bound Ru(III), generated through a flash/quench technique, is found to promote oxidation of the [4Fe-4S](2+) cluster of MutY to [4Fe-4S](3+) and its decomposition product [3Fe-4S](1+). Flash/quench experiments monitored by EPR spectroscopy reveal spectra with g = 2.08, 2.06, and 2.02, characteristic of the oxidized clusters. Transient absorption spectra of poly(dGC) and [Ru(phen)(2)dppz](3+) (dppz = dipyridophenazine), generated in situ, show an absorption characteristic of the guanine radical that is depleted in the presence of MutY with formation instead of a long-lived species with an absorption at 405 nm; we attribute this absorption also to formation of the oxidized [4Fe-4S](3+) and [3Fe4S](1+) clusters. In ruthenium-tethered DNA assemblies, oxidative damage to the 5'-G of a 5'-GG-3' doublet is generated from a distance but this irreversible damage is inhibited by MutY and instead EPR experiments reveal cluster oxidation. With ruthenium-tethered assemblies containing duplex versus single-stranded regions, MutY oxidation is found to be mediated by the DNA duplex, with guanine radical as an intermediate oxidant; guanine radical formation facilitates MutY oxidation. A model is proposed for the redox activation of DNA repair proteins through DNA CT, with guanine radicals, the first product under oxidative stress, in oxidizing the DNA-bound repair proteins, providing the signal to stimulate DNA repair.

Item Type:Article
Additional Information:Copyright © 2005 by the National Academy of Sciences. Edited by Harry B. Gray, California Institute of Technology, Pasadena, CA, and approved January 19, 2005 (received for review December 16, 2004). This paper was submitted directly (Track II) to the PNAS office. We thank the National Institutes of Health for their financial support of this research.
Subject Keywords:electron transfer, iron-sulfur cluster, oxidative DNA damage, range electron-transfer, flash-quench technique, Escherichia-coli muty, long-range, duplex DNA, glycosylase muty, oxidative damage, ruthenium complexes, endonuclease-III, sequence
Record Number:CaltechAUTHORS:YAVpnas05
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:970
Deposited By: Tony Diaz
Deposited On:17 Nov 2005
Last Modified:14 Nov 2014 19:18

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