DNA-processing repair proteins containing redox-active [4Fe4S] metallocofactors facilitate DNA lesion detection

Abstract

DNA stores vital genetic information from which the foundation of life is built upon. Oxidative stress poses a recurrent threat to genome integrity and a continual risk of cancer development. The ability for charge to be transferred through DNA has implications in its structural maintenance assisted by repair proteins carrying redox-active [4Fe4S] clusters. In this presentation, I will present our work on establishing the importance of the redox state of the [4Fe4S] inorg. cofactor in the DNA damage detection process. Specifically, [4Fe4S] clusters primarily in the oxidized state abolish the ability of repair proteins to differentiate between well-matched and damaged DNA strands. Conversely, [4Fe4S] metallocofactors primarily in the reduced state enable repair proteins to redistribute onto DNA duplexes contg. a C:A mismatch. We further devised a biophys. model that focuses on the electrostatic interactions between [4Fe4S] cluster proteins and DNA to explain the exptl. obsd. change in DNA binding affinity upon switching the oxidn. state of the [4Fe4S] cluster proteins. I will also present our new findings on how far and how fast electrons travel across DNA duplexes. Techniques: (i) DNA-modified electrode, (ii) at.-force-microscopy-based redistribution assay, (iii) gel-based electrophoretic mobility shift assay, (iv) biophys. electrostatic differential binding model, (v) ESR, (vi) UV-visible spectroscopy, (vii) electrochem., (viii) CD. Significance: Repair proteins carrying [4Fe4S] clusters modulate their binding strength to DNA by switching the redox state of the [4Fe4S] inorg. cofactors to regulate the ability of the repair proteins to search for DNA damage via DNA-mediated charge transfer in response to cellular oxidative stress. Figure Captions: (A) Biophys. electrostatic model, (B) DNA-modified electrode to generate primarily reduced or oxidized proteins carrying [4Fe4S] clusters, and (C) DNA damage search mechanism enabled by DNA-mediated electron transport.

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