Enzymology of the repair of free radicals-induced DNA damage

Abstract

A number of intrinsic and extrinsic mutagens induce structural damage in cellular DNA. These DNA damages are cytotoxic, miscoding or both and are believed to be at the origin of cell lethality, tissue degeneration, ageing and cancer. In order to counteract immediately the deleterious effects of such lesions, leading to genomic instability, cells have evolved a number of DNA repair mechanisms including the direct reversal of the lesion, sanitation of the dNTPs pools, mismatch repair and several DNA excision pathways including the base excision repair (BER) nucleotide excision repair (NER) and the nucleotide incision repair (NIR). These repair pathways are universally present in living cells and extremely well conserved. This review is focused on the repair of lesions induced by free radicals and ionising radiation. The BER pathway removes most of these DNA lesions, although recently it was shown that other pathways would also be efficient in the removal of oxidised bases. In the BER pathway the process is initiated by a DNA glycosylase excising the modified and mismatched base by hydrolysis of the glycosidic bond between the base and the deoxyribose of the DNA, generating a free base and an abasic site (AP-site) which in turn is repaired since it is cytotoxic and mutagenic.

Hijacking of the Human Alkyl-N-purine-DNA Glycosylase by 3,N4-Ethenocytosine, a Lipid Peroxidation-induced DNA Adduct

“…The weak inhibition by ⑀A⅐T and I⅐T might be due to the high K m value of ANPG for these substrates (24 and 69 nM, respectively) (41,42). No significant effect on ⑀A-DNA glycosylase activity of ANPG was detected in the presence of C⅐G, G⅐T, G⅐U, THF⅐G, 8-oxoG⅐C, 8-oxoG⅐A, 5ohU⅐G, DHU⅐G, DHT⅐A, and I⅐T oligonucleotides, even at 8-fold molar excess (lanes 3-8, lanes [13][14][15][16], and data not shown). 2-and 20-fold reductions of the incision were observed in the presence of 1-and 8-fold molar excess of ⑀C⅐G, respectively (lanes [11][12], indicating that ⑀C is a more efficient inhibitor than ⑀A (or Hx) (lanes 10 and 12).…”

“…2 A, schematic representation of the 5Ј-flap structure DNA template containing either a C⅐G or a ⑀C⅐G base pair and possible elongation products: 41-mer, full-sized product; 25-mer, ⑀C termination product; 20-mer, ANPG⅐⑀C termination product; 13-mer, 5Ј-32 P-labeled primer. B, 10 nM 5Ј-32 P-labeled C⅐G (lanes 1-8) and/or ⑀C⅐G (lanes 9 -16) primer/ template were incubated with (lanes 3-8 and lanes [11][12][13][14][15][16] or without (lanes 1-2 and lanes 9 -10) 1 unit of Klenow fragment, and the primer extension reaction was performed for 5 min at 37°C. Lanes 1 and 9, no enzyme; lanes 2 and 10, 500 nM ANPG80; lanes 3 and 11, 10 nM ANPG80; lanes 4 and 12, 20 nM ANPG80; lanes 5 and 13, 50 nM ANPG80; lanes 6 and 14, 100 nM ANPG80; lanes 7 and 15, 200 nM ANPG80; lanes 8 and 16, 500 nM ANPG80.…”

A unified view of base excision repair: Lesion-dependent protein complexes regulated by post-translational modification

“…Persistent genomic instability is thought to be a critical step toward the transformation of cells to a cancerous state [48]. Ionizing radiation generates a bolus of oxygen radical in the water surrounding the DNA molecule, resulting in a clustering effect of the damage [49]. Interestingly, these radiation induced breaks are reported to exist primarily as 5'-phosphate and equal amounts of either 3'-phosphate or 3'-phosphoglycolates at the margins of the gap [50][51][52].…”

Mitochondrial respiratory chain dysfunction: Implications in neurodegeneration

“…Therefore, if ROS are not efficiently eliminated by the cellular antioxidants the cellular components become damaged by oxidation, which in turn leads to further oxidative stress, cellular dysfunction and even cell death (for a review in cellular antioxidants, repair of oxidative damage and their implication in neurodegeneration see Gros et al, 2002;Ahsan et al, 2009;Fernandez-Checa et al, 2010).…”