title: Binary complex crystal structure of DNA polymerase β reveals multiple conformations of the templating 8-oxoguanine lesion.
abstract: Oxidation of genomic DNA forms the guanine lesion 7,8-dihydro-8-oxoguanine (8-oxoG). When in the template base position during DNA synthesis the 8-oxoG lesion has dual coding potential by virtue of its anti- and syn-conformations, base pairing with cytosine and adenine, respectively. This impacts mutagenesis, because insertion of adenine opposite template 8-oxoG can result in a G to T transversion. DNA polymerases vary by orders of magnitude in their preferences for mutagenic vs. error-free 8-oxoG lesion bypass. Yet, the structural basis for lesion bypass specificity is not well understood. The DNA base excision repair enzyme DNA polymerase (pol) β is presented with gap-filling synthesis opposite 8-oxoG during repair and has similar insertion efficiencies for dCTP and dATP. We report the structure of pol β in binary complex with template 8-oxoG in a base excision repair substrate. The structure reveals both the syn- and anti-conformations of template 8-oxoG in the confines of the polymerase active site, consistent with the dual coding observed kinetically for this enzyme. A ternary complex structure of pol β with the syn-8-oxoG:anti-A Hoogsteen base pair in the closed fully assembled preinsertion active site is also reported. The syn-conformation of 8-oxoG is stabilized by minor groove hydrogen bonding between the side chain of Arg283 and O8 of 8-oxoG. An adjustment in the position of the phosphodiester backbone 5'-phosphate enables 8-oxoG to adopt the syn-conformation.
authors.affiliation: Laboratory of Structural Biology, National Institute of Environmental Health Sciences, National Institutes of Health, P.O. Box 12233, Research Triangle Park, NC 27709-2233, USA.
authors.forename: Vinod K
authors.initials: VK
authors.lastname: Batra
authors.forename: David D
authors.initials: DD
authors.lastname: Shock
authors.forename: William A
authors.initials: WA
authors.lastname: Beard
authors.forename: Charles E
authors.initials: CE
authors.lastname: McKenna
authors.forename: Samuel H
authors.initials: SH
authors.lastname: Wilson
mesh_terms: D020029:Base Pairing; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004249:DNA Damage; D019951:DNA Polymerase beta / Q000737:chemistry* / Q000378:metabolism; D006147:Guanine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D016296:Mutagenesis / Q000235:genetics; D011487:Protein Conformation; D013698:Templates, Genetic
chemical_list: C024829:8-hydroxyguanine; D006147:Guanine; D019951:DNA Polymerase beta