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

Yavin, E., Boal, A.K., Stemp, E.D.A., Boon, E.M., Livingston, A.L., O'Shea, V. , David, S.S. and Barton, J.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.

Abstract

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)2dppz]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 [3Fe-4S]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: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: O'Shea, Professor Val
• Authors: Yavin, E., Boal, A.K., Stemp, E.D.A., Boon, E.M., Livingston, A.L., O'Shea, V., David, S.S., and Barton, J.K.
• College/School: College of Science and Engineering > School of Physics and Astronomy
• Journal Name: Proceedings of the National Academy of Sciences of the United States of America
• Publisher: National Academy of Sciences
• ISSN: 0027-8424
• ISSN (Online): 1091-6490