Citation

DeMott MS, Beyret E, Wong D, Bales BC, Hwang JT, Greenberg MM, Demple B. J. Biol. Chem. 2002; 277(10): 7637-7640.

Copyright

(Copyright © 2002, American Society for Biochemistry and Molecular Biology)

DOI

10.1074/jbc.C100577200

PMID

11805079

Abstract

Oxidized abasic residues in DNA constitute a major class of radiation and oxidative damage. Free radical attack on the nucleotidyl C-1' carbon yields 2-deoxyribonolactone (dL) as a significant lesion. Although dL residues are efficiently incised by the main human abasic endonuclease enzyme Ape1, we show here that subsequent excision by human DNA polymerase beta is impaired at dL compared with unmodified abasic sites. This inhibition is accompanied by accumulation of a protein-DNA cross-link not observed in reactions of polymerase beta with unmodified abasic sites, although a similar form can be trapped by reduction with sodium borohydride. The formation of the stably cross-linked species with dL depends on the polymerase lysine 72 residue, which forms a Schiff base with the C-1 aldehyde during excision of an unmodified abasic site. In the case of a dL residue, attack on the lactone C-1 by lysine 72 proceeds more slowly and evidently produces an amide linkage, which resists further processing. Consequently dL residues may not be readily repaired by "short-patch" base excision repair but instead function as suicide substrates in the formation of protein-DNA cross-links that may require alternative modes of repair.

Language: en

Keywords

Cross-Linking Reagents; DNA; DNA Damage; DNA Polymerase beta; Electrophoresis, Polyacrylamide Gel; Free Radicals; Humans; Lysine; Models, Chemical; Oxidative Stress; Oxygen; Protein Binding; Sugar Acids