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Covalent Trapping of Human DNA Polymerase β by the Oxidative DNA Lesion 2-Deoxyribonolactone*

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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 β 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 β 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.

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Published, JBC Papers in Press, January 22, 2002, DOI 10.1074/jbc.C100577200

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This work was supported by National Institutes of Health Grants CA71993 (to B. D. and M. M. G.), GM40000 (to B. D.), and GM54996 and CA74954 (to M. M. G.). General support was through the Kresge Center for Environmental Health Sciences of Harvard School of Public Health.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

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Supported by Training Grant T32-CA09078 from the NCI, National Institutes of Health.

Supported in part by Training Grant T32-ES07155 from the NIEHS, National Institutes of Health.