title: Preferential recognition of I.T base-pairs in the initiation of excision-repair by hypoxanthine-DNA glycosylase.
abstract: Double-stranded synthetic oligonucleotides with a centrally located dIMP residue in a 5'-32P-labeled strand were employed as substrates for hypoxanthine-DNA glycosylase. The enzyme activity was monitored by the generation of a piperidine-sensitive site in the labeled oligonucleotide. The enzyme was purified approximately 5000-fold from calf thymus. The purified enzyme removed efficiently a hypoxanthine base residue from an I.T base pair, but 15-20 times more slowly from an I.C base pair. Similar results were obtained with oligonucleotides in which the deoxyinosine residue was placed in different surrounding nucleotide sequences. The enzyme had no detectable activity on mismatched G.T, A.G or A.C base pairs. The data indicate that hypoxanthine-DNA glycosylase participates in the repair of deaminated adenine residues in DNA.
authors.affiliation: Imperial Cancer Research Fund, Clare Hall Laboratories, South Mimms, Herts UK.
authors.forename: G
authors.initials: G
authors.lastname: Dianov
authors.forename: T
authors.initials: T
authors.lastname: Lindahl
mesh_terms: D001482:Base Composition; D001483:Base Sequence; D004260:DNA Repair; D006026:Glycoside Hydrolases / Q000378:metabolism*; D006868:Hydrolysis; D007288:Inosine / Q000737:chemistry; D007700:Kinetics; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides / Q000737:chemistry / Q000378:metabolism; D013379:Substrate Specificity; D013941:Thymine / Q000737:chemistry
chemical_list: D009838:Oligodeoxyribonucleotides; D007288:Inosine; D006026:Glycoside Hydrolases; C035336:DNA-deoxyinosine glycosidase; D013941:Thymine