title: Reactivity of cytosine and thymine in single-base-pair mismatches with hydroxylamine and osmium tetroxide and its application to the study of mutations.
abstract: The chemical reactivity of thymine (T), when mismatched with the bases cytosine, guanine, and thymine, and of cytosine (C), when mismatched with thymine, adenine, and cytosine, has been examined. Heteroduplex DNAs containing such mismatched base pairs were first incubated with osmium tetroxide (for T and C mismatches) or hydroxylamine (for C mismatches) and then incubated with piperidine to cleave the DNA at the modified mismatched base. This cleavage was studied with an internally labeled strand containing the mismatched T or C, such that DNA cleavage and thus reactivity could be detected by gel electrophoresis. Cleavage at a total of 13 T and 21 C mismatches isolated (by at least three properly paired bases on both sides) single-base-pair mismatches was identified. All T or C mismatches studied were cleaved. By using end-labeled DNA probes containing T or C single-base-pair mismatches and conditions for limited cleavage, we were able to show that cleavage was at the base predicted by sequence analysis and that mismatches in a length of DNA could be readily detected by such an approach. This procedure may enable detection of all single-base-pair mismatches by use of sense and antisense probes and thus may be used to identify the mutated base and its position in a heteroduplex.
authors.affiliation: Department of Biochemistry, University of Oxford, United Kingdom.
authors.forename: R G
authors.initials: RG
authors.lastname: Cotton
authors.forename: N R
authors.initials: NR
authors.lastname: Rodrigues
authors.forename: R D
authors.initials: RD
authors.lastname: Campbell
mesh_terms: D001482:Base Composition; D003001:Cloning, Molecular; D003596:Cytosine; D004247:DNA / Q000187:drug effects / Q000235:genetics*; D005796:Genes; D019811:Hydroxylamine; D006898:Hydroxylamines / Q000494:pharmacology*; D009154:Mutation; D009692:Nucleic Acid Heteroduplexes; D009992:Osmium / Q000494:pharmacology; D009993:Osmium Tetroxide / Q000494:pharmacology*; D010957:Plasmids; D013255:Steroid 21-Hydroxylase / Q000235:genetics; D013941:Thymine
chemical_list: D006898:Hydroxylamines; D009692:Nucleic Acid Heteroduplexes; D009992:Osmium; D019811:Hydroxylamine; D003596:Cytosine; D004247:DNA; D013255:Steroid 21-Hydroxylase; D009993:Osmium Tetroxide; D013941:Thymine