title: O(6) -alkylguanine-DNA alkyltransferase-mediated repair of O(4) -alkylated 2'-deoxyuridines.
abstract: O(6) -Alkylguanine-DNA alkyltransferases (AGTs) are responsible for the removal of O(6) -alkyl 2'-deoxyguanosine (dG) and O(4) -alkyl thymidine (dT) adducts from the genome. Unlike the E. coli OGT (O(6) -alkylguanine-DNA-alkyltransferase) protein, which can repair a range of O(4) -alkyl dT lesions, human AGT (hAGT) only removes methyl groups poorly. To uncover the influence of the C5 methyl group of dT on AGT repair, oligonucleotides containing O(4) -alkyl 2'-deoxyuridines (dU) were prepared. The ability of E. coli AGTs (Ada-C and OGT), human AGT, and an OGT/hAGT chimera to remove O(4) -methyl and larger adducts (4-hydroxybutyl and 7-hydroxyheptyl) from dU were examined and compared to those relating to the corresponding dT species. The absence of the C5 methyl group resulted in an increase in repair observed for the O(4) -methyl adducts by hAGT and the chimera. The chimera was proficient at repairing larger adducts at the O(4) atom of dU. There was no observed correlation between the binding affinities of the AGT homologues to adduct-containing oligonucleotides and the amounts of repair measured.
authors.affiliation: Department of Chemistry and Biochemistry, Concordia University, Montreal, Quebec, H4B 1R6 (Canada).
authors.forename: Francis P
authors.initials: FP
authors.lastname: McManus
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Wilds
mesh_terms: D000478:Alkylation; D002678:Chimera; D018736:DNA Adducts / Q000187:drug effects; D004260:DNA Repair / Q000502:physiology*; D003857:Deoxyuridine / Q000737:chemistry*; D018257:Helix-Loop-Helix Motifs; D006801:Humans; D009691:Nucleic Acid Denaturation; D019853:O(6)-Methylguanine-DNA Methyltransferase / Q000378:metabolism*; D009841:Oligonucleotides / Q000138:chemical synthesis; D011743:Pyrimidines / Q000737:chemistry; D014466:Ultraviolet Rays
chemical_list: D018736:DNA Adducts; D009841:Oligonucleotides; D011743:Pyrimidines; D019853:O(6)-Methylguanine-DNA Methyltransferase; D003857:Deoxyuridine
keywords: DNA; DNA damage; bioorganic chemistry; nucleosides; oligonucleotides