Investigating the mechanism of ferritin protection of DNA

点击翻译按钮获取中文摘要

DESCRIPTION (provided by applicant): While aging is a complex, multidimensional process that is not yet fully understood, the accumulation of DNA damage has long been recognized as an important factor in aging. The iron storage protein ferritin is a significant player in the defensive strategy of the cell. These proteins deplete ferrous iron and hydrogen peroxide, which can otherwise produce damaging oxygen radicals via the Fenton reaction. While ferritin was traditionally believed to be present solely in the cytoplasm, it recently has been found in cell nuclei, opening up new possibilities for direct DNA protection by ferritin. This study will focus on elucidating the mechanism of ferritin protection of DNA. Dps, a bacterial ferritin whose DNA binding has been extensively studied, will be used as a model for the ferritin family. The ability of DNA to conduct charge through its base stack has been well-studied and DNA charge transfer (CT) processes have been proposed to be biologically relevant in a number of systems such as the activation of redox sensitive transcription factors. In this work, we will determine if the ferritin Dps can protect the genome from a distance by utilizing charge transport through DNA. This will be achieved by combining various spectroscopies with the flash-quench technique, a method to generate a powerful oxidant in situ that is capable of oxidizing DNA. Upon oxidation, the lack of an electron (hole) localizes on guanine, the most easily oxidized base. However, we hypothesize that DNA- bound Dps can become oxidized via DNA CT to fill the hole on the guanine and restore the integrity of the DNA. Transient absorption and electron paramagnetic resonance spectroscopies can monitor guanine radicals and protein oxidation products, and can therefore be used to determine if ferritin can protect DNA from a distance by becoming oxidized in a DNA- mediated process. This work seeks to expand the general mechanisms of protection to include protection from a distance, in the hopes of elucidating one aspect of the dynamic interplay between DNA damage and repair that contributes to aging and age-related disease.