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Epigenetic alterations can accompany DNA repair of oxidative damage or double-strand breaks. In human cells, oxidative DNA damage occurs about 10,000 times a day and DNA double-strand breaks occur about 10 to 50 times a cell cycle in somatic replicating cells (see DNA damage (naturally occurring)). The selective advantage of DNA repair is to ...
DNA oxidation is the process of oxidative damage of deoxyribonucleic acid.As described in detail by Burrows et al., [1] 8-oxo-2'-deoxyguanosine (8-oxo-dG) is the most common oxidative lesion observed in duplex DNA because guanine has a lower one-electron reduction potential than the other nucleosides in DNA.
DNA repair enzymes include endonuclease IV, induced by oxidative stress, and exonuclease III, induced in the stationary phase and in starving cells. These enzymes act on duplex DNA and clean up DNA 3' terminal ends. Prokaryotic cells contain catalysts that modify the primary structure of proteins frequently by reducing disulfide bonds.
Normal cellular defense mechanisms destroy most of these. Repair of oxidative damages to DNA is frequent and ongoing, largely keeping up with newly induced damages. In rat urine, about 74,000 oxidative DNA adducts per cell are excreted daily. [27] There is also a steady state level of oxidative damages in the DNA of a cell.
Naturally occurring oxidative DNA damages arise at least 10,000 times per cell per day in humans and as much as 100,000 per cell per day in rats [9] as documented below. Oxidative DNA damage can produce more than 20 types of altered bases [10] [11] as well as single strand breaks. [12]
For eukaryotes, oxidative reactions are a major source of DNA damage (see DNA damage (naturally occurring) and Sedelnikova et al. [23]). In humans, about 10,000 oxidative DNA damages occur per cell per day. [24] In the rat, which has a higher metabolic rate than humans, about 100,000 oxidative DNA damages occur per cell per day.
The SOS response is a global response to DNA damage in which the cell cycle is arrested and DNA repair and mutagenesis are induced. The system involves the RecA protein ( Rad51 in eukaryotes). The RecA protein, stimulated by single-stranded DNA, is involved in the inactivation of the repressor ( LexA ) of SOS response genes thereby inducing the ...
Hydroxyl radicals can attack the deoxyribose DNA backbone and bases, potentially causing a plethora of lesions that can be cytotoxic or mutagenic. Cells have developed complex and efficient repair mechanisms to fix the lesions. In the case of free radical attack on DNA, base-excision repair is the repair mechanism used. Hydroxyl radical ...