title: Oxygen free radical damage to DNA. Translesion synthesis by human DNA polymerase eta and resistance to exonuclease action at cyclopurine deoxynucleoside residues.
abstract: Cyclopurine deoxynucleosides are common DNA lesions generated by exposure to reactive oxygen species under hypoxic conditions. The S and R diastereoisomers of cyclodeoxyadenosine on DNA were investigated separately for their ability to block 3' to 5' exonucleases. The mammalian DNA-editing enzyme DNase III (TREX1) was blocked by both diastereoisomers, whereas only the S diastereoisomer was highly efficient in preventing digestion by the exonuclease function of T4 DNA polymerase. Digestion in both cases was frequently blocked one residue before the modified base. Oligodeoxyribonucleotides containing a cyclodeoxyadenosine residue were further employed as templates for synthesis by human DNA polymerase eta (pol eta). pol eta could catalyze translesion synthesis on the R diastereoisomer of cyclodeoxyadenosine. On the S diastereoisomer, pol eta could catalyze the incorporation of one nucleotide opposite the lesion but could not continue elongation. Although pol eta preferentially incorporated dAMP opposite the R diastereoisomer, elongation continued only when dTMP was incorporated, suggesting bypass of this lesion by pol eta with reasonable fidelity. With the S diastereoisomer, pol eta mainly incorporated dAMP or dTMP opposite the lesion but could not elongate even after incorporating a correct nucleotide. These data suggest that the S diastereoisomer may be a more cytotoxic DNA lesion than the R diastereoisomer.
authors.affiliation: Imperial Cancer Research Fund, Clare Hall Laboratories, South Mimms, Hertfordshire EN6 3LD, United Kingdom.
authors.forename: I
authors.initials: I
authors.lastname: Kuraoka
authors.forename: P
authors.initials: P
authors.lastname: Robins
authors.forename: C
authors.initials: C
authors.lastname: Masutani
authors.forename: F
authors.initials: F
authors.lastname: Hanaoka
authors.forename: D
authors.initials: D
authors.lastname: Gasparutto
authors.forename: J
authors.initials: J
authors.lastname: Cadet
authors.forename: R D
authors.initials: RD
authors.lastname: Wood
authors.forename: T
authors.initials: T
authors.lastname: Lindahl
mesh_terms: D004249:DNA Damage; D004260:DNA Repair; D004261:DNA Replication / Q000235:genetics; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D005092:Exonucleases / Q000378:metabolism*; D005609:Free Radicals; D006801:Humans; D008958:Models, Molecular; D015394:Molecular Structure; D009841:Oligonucleotides / Q000737:chemistry* / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D000099270:Y-Family DNA Polymerases
chemical_list: D004259:DNA-Directed DNA Polymerase; D005092:Exonucleases; D005609:Free Radicals; D009841:Oligonucleotides; D017382:Reactive Oxygen Species; C112338:Rad30 protein; D000099270:Y-Family DNA Polymerases