Table I.
Sources, types, frequency and consequences of several BER substrates
| Lesion source | Lesion type | Lesion frequency (per 10e6 bases) | Toxicity | Mutagenicity | Repair enzyme/pathway |
|---|---|---|---|---|---|
| Hydrolysis | Deoxyuracil | 1 | +++ | UNG, SMUG1 | |
| AP site | 3–20 | +++ | + | APE1 | |
| Alkylation | 7-methyl guanine | 1 | Not repaired | ||
| 3-methyl adenine | 0.1 | ++ | MPG | ||
| O6-methyl guanine | 0.01 | + | +++ | Direct reversal | |
| Oxidation | 8oxoG | 1–10 | + | +++ | OGG1, MUTYH |
| Ethenoadenine | 0.05 | +++ | +++ | AlkB homologs | |
| Ethenocytosine | 0.2 | +++ | +++ | AlkB homologs | |
| Hydroxycytidine | 1 | ++ | NTH1, NEIL1 | ||
| Thymine glycol | 2 | +++ | + | NTH1, NEIL1 | |
| FaPyG | 0.6a | ++ | OGG1, NTH1, NEIL1 | ||
| FaPyA | 0.8a | ++ | +++ | NEIL1 |
Table is adapted from references (2,5), with frequency data tailored specifically to frequency of lesions in leukocytes, except for the FaPy lesions. The toxicity and mutagenicity columns are presented as general guidance (with degree increasing with + symbol). The measured levels of any given DNA lesion tend to vary by orders of magnitude depending on sampled tissue and measurement technique. FaPy, formamidopyrimidine; SMUG1, single-strand selective monofunctional uracil glycosylase. aData from other cell types.