Base Excision Repair, AP Endonucleases and DNA Glycosylases


Base excision repair is an important cellular mechanism that protects the integrity of DNA by repairing damage caused by alkylating agents and reactive oxygen species. The altered DNA base, and in some cases a few nucleotides adjacent to the altered base, is removed by excision, and the DNA is repaired by DNA synthesis and ligation.

Keywords: DNA repair; DNA damage; mutation; polymerase; nuclease

Figure 1.

DNA lesions repaired by base excision repair.

Figure 2.

Single‐nucleotide and alternate base excision repair pathways dRP, 5′‐deoxyribosephosphate; PCNA, proliferating cell nuclear antigen; FEN‐1, flap endonuclease 1.

Figure 3.

DNA polymerase β has two helix‐hairpin‐helix (HhH) motifs. The two HhH motifs (white) of DNA polymerase β (red) bind to the sugar–phosphate backbone on both sides of the gapped DNA strand (blue).

Figure 4.

Cleavage of an abasic site. Products of cleavage by AP endonuclease have 3′‐hydroxyl and 5′‐deoxyribosephosphate termini (lower right) and products of cleavage by AP lyase have 5′‐phosphate and 3′‐deoxyribosephosphate termini (upper right).

Figure 5.

Ternary complex structure of DNA polymerase β. The incoming ddCTP (yellow) is observed to be hydrogen bonded to a guanine residue (red) in the template strand. The DNA is omitted for clarity. The N‐terminal 8‐kDa domain (white) is situated above the C‐terminal polymerase domain (blue).



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Sander, Miriam, and Wilson, Samuel H(May 2005) Base Excision Repair, AP Endonucleases and DNA Glycosylases. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1038/npg.els.0003871]