title: Structure and specificity of the vertebrate anti-mutator uracil-DNA glycosylase SMUG1.
abstract: Cytosine deamination is a major promutagenic process, generating G:U mismatches that can cause transition mutations if not repaired. Uracil is also introduced into DNA via nonmutagenic incorporation of dUTP during replication. In bacteria, uracil is excised by uracil-DNA glycosylases (UDG) related to E. coli UNG, and UNG homologs are found in mammals and viruses. Ung knockout mice display no increase in mutation frequency due to a second UDG activity, SMUG1, which is specialized for antimutational uracil excision in mammalian cells. Remarkably, SMUG1 also excises the oxidation-damage product 5-hydroxymethyluracil (HmU), but like UNG is inactive against thymine (5-methyluracil), a chemical substructure of HmU. We have solved the crystal structure of SMUG1 complexed with DNA and base-excision products. This structure indicates a more invasive interaction with dsDNA than observed with other UDGs and reveals an elegant water displacement/replacement mechanism that allows SMUG1 to exclude thymine from its active site while accepting HmU.
authors.affiliation: Cancer Research UK DNA Repair Enzyme Group, Section of Structural Biology, The Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London SW3 6JB, United Kingdom.
authors.forename: Jane E A
authors.initials: JE
authors.lastname: Wibley
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Waters
authors.forename: Karl
authors.initials: K
authors.lastname: Haushalter
authors.forename: Gregory L
authors.initials: GL
authors.lastname: Verdine
authors.forename: Laurence H
authors.initials: LH
authors.lastname: Pearl
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D020137:Base Pair Mismatch; D020029:Base Pairing; D001483:Base Sequence; D003596:Cytosine / Q000378:metabolism; D004249:DNA Damage; D045647:DNA Glycosylases; D004260:DNA Repair; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009154:Mutation; D009699:N-Glycosyl Hydrolases / Q000737:chemistry*; D010432:Pentoxyl / Q000031:analogs & derivatives* / Q000378:metabolism; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D051981:Uracil-DNA Glycosidase; D029867:Xenopus Proteins; D014982:Xenopus laevis
chemical_list: D029867:Xenopus Proteins; C008055:5-hydroxymethyluracil; D010432:Pentoxyl; D003596:Cytosine; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; C498096:SMUG1 protein, Xenopus laevis; C498095:SMUG1 protein, human; D051981:Uracil-DNA Glycosidase