ATP insertion opposite 8-oxo-deoxyguanosine by Pol4 mediates error-free tolerance in Schizosaccharomyces pombe.
Bottom Line: In cell extracts, misincorporation of ATP opposite 8oxodG was shown to be SpPol4-specific, although RNase H2 efficiently recognized the 8oxodG:AMP mispair to remove AMP and trigger error-free incorporation of dCTP.Moreover, we demonstrate that purified SpPol4 uses 8oxo-dGTP and 8oxo-GTP as substrates for DNA polymerization, although with poor efficiency compared to the incorporation of undamaged nucleotides opposite either 8oxodG or undamaged templates.This suggests that SpPol4 is specialized in tolerating 8oxodG as a DNA template, without contributing significantly to the accumulation of this lesion in the DNA.
Affiliation: Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), Universidad Autónoma, 28049 Madrid, Spain.Show MeSH
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Mentions: One of the most common lesions generated by oxidative stress is 8oxodG. It arises in the DNA upon guanine oxidation (Figure 9A), and is promutagenic due to its ability to mispair with adenine. In mammalian cells, 8oxodG is mainly repaired by BER, in a process initiated by OGG1 (homolog of MutM in E. coli). The absence of an OGG1 homologue in S. pombe suggests that 8oxodG:dC base pairs could be left unrepaired, thus promoting misincorporation of dATP most likely during DNA replication with a potential impact in mutagenesis (Figure 9A). However, most of these errors should be eliminated by MutY, conserved in fission yeast (SpMYH), by excising the adenine from 8oxodG:dA base pairs (20) (Figure 9A). Coupled to the action of MutY homologs (MYH), a specialized polymerase able to copy 8oxodG in an error-free manner is considered indispensable to avoid mutagenesis, as replicative DNA polymerases display a reduced efficiency and fidelity when tolerating this lesion.
Affiliation: Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), Universidad Autónoma, 28049 Madrid, Spain.