title: Oxanine DNA glycosylase activity from Mammalian alkyladenine glycosylase.
abstract: Oxanine (Oxa) is a deaminated base lesion derived from guanine in which the N(1)-nitrogen is substituted by oxygen. This work reports the mutagenicity of oxanine as well as oxanine DNA glycosylase (ODG) activities in mammalian systems. Using human DNA polymerase beta, deoxyoxanosine triphosphate is only incorporated opposite cytosine (Cyt). When an oxanine base is in a DNA template, Cyt is efficiently incorporated opposite the template oxanine; however, adenine and thymine are also incorporated opposite Oxa with an efficiency approximately 80% of a Cyt/Oxa (C/O) base pair. Guanine is incorporated opposite Oxa with the least efficiency, 16% compared with cytosine. ODG activity was detected in several mammalian cell extracts. Among the known human DNA glycosylases tested, human alkyladenine glycosylase (AAG) shows ODG activity, whereas hOGG1, hNEIL1, or hNEIL2 did not. ODG activity was detected in spleen cell extracts of wild type age-matched mice, but little activity was observed in that of Aag knock-out mice, confirming that the ODG activity is intrinsic to AAG. Human AAG can excise Oxa from all four Oxa-containing double-stranded base pairs, Cyt/Oxa, Thy/Oxa, Ade/Oxa, and Gua/Oxa, with no preference to base pairing. Surprisingly, AAG can remove Oxa from single-stranded Oxa-containing DNA as well. Indeed, AAG can also remove 1,N(6)-ethenoadenine from single-stranded DNA. This study extends the deaminated base glycosylase activities of AAG to oxanine; thus, AAG is a mammalian enzyme that can act on all three purine deamination bases, hypoxanthine, xanthine, and oxanine.
authors.affiliation: Department of Genetics, Biochemistry & Life Science Studies, South Carolina Experiment Station, Clemson University, Clemson, South Carolina 29634, USA.
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Hitchcock
authors.forename: Liang
authors.initials: L
authors.lastname: Dong
authors.forename: Ellen E
authors.initials: EE
authors.lastname: Connor
authors.forename: Lisiane B
authors.initials: LB
authors.lastname: Meira
authors.forename: Leona D
authors.initials: LD
authors.lastname: Samson
authors.forename: Michael D
authors.initials: MD
authors.lastname: Wyatt
authors.forename: Weiguo
authors.initials: W
authors.lastname: Cao
mesh_terms: D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003596:Cytosine / Q000737:chemistry; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D045647:DNA Glycosylases / Q000378:metabolism*; D019951:DNA Polymerase beta / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000378:metabolism; D006147:Guanine / Q000737:chemistry; D006801:Humans; D019271:Hypoxanthine / Q000737:chemistry; D051379:Mice; D018345:Mice, Knockout; D016297:Mutagenesis, Site-Directed; D009693:Nucleic Acid Hybridization; D009711:Nucleotides / Q000737:chemistry; D009841:Oligonucleotides / Q000737:chemistry; D011485:Protein Binding; D011684:Purine Nucleosides / Q000737:chemistry*; D013154:Spleen / Q000378:metabolism; D013552:Swine; D013950:Thymus Gland / Q000378:metabolism; D013997:Time Factors; D019820:Xanthine / Q000737:chemistry
chemical_list: D004277:DNA, Single-Stranded; D009711:Nucleotides; D009841:Oligonucleotides; D011684:Purine Nucleosides; C468766:oxanine; D019820:Xanthine; D019271:Hypoxanthine; D006147:Guanine; D003596:Cytosine; D004247:DNA; D019951:DNA Polymerase beta; C021565:3-methyladenine-DNA glycosylase; D045647:DNA Glycosylases