Enforced Presentation of an Extrahelical Guanine to the Lesion Recognition Pocket of Human 8-Oxoguanine Glycosylase, hOGG1

Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
Journal of Biological Chemistry (Impact Factor: 4.57). 04/2012; 287(30):24916-28. DOI: 10.1074/jbc.M111.316497
Source: PubMed


A poorly understood aspect of DNA repair proteins is their ability to identify exceedingly rare sites of damage embedded in a large excess of nearly identical undamaged DNA, while catalyzing repair only at the damaged sites. Progress toward understanding this problem has been made by comparing the structures and biochemical behavior of these enzymes when they are presented with either a target lesion or a corresponding undamaged nucleobase. Trapping and analyzing such DNA-protein complexes is particularly difficult in the case of base extrusion DNA repair proteins because of the complexity of the repair reaction, which involves extrusion of the target base from DNA followed by its insertion into the active site where glycosidic bond cleavage is catalyzed. Here we report the structure of a human 8-oxoguanine (oxoG) DNA glycosylase, hOGG1, in which a normal guanine from DNA has been forcibly inserted into the enzyme active site. Although the interactions of the nucleobase with the active site are only subtly different for G versus oxoG, hOGG1 fails to catalyze excision of the normal nucleobase. This study demonstrates that even if hOGG1 mistakenly inserts a normal base into its active site, the enzyme can still reject it on the basis of catalytic incompatibility.

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Available from: Gregory L Verdine, Dec 18, 2013
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    • "It thus appears that the observed dipole is not mandatory for 8-oxoG discrimination or catalysis. This observation seems to be corroborated by the structure of hOGG1 in complex with guanine (PDB ID: 3IH7 [48]) in which the guanine base occupies the exact same position as observed for 8-oxoG in the hOGG1-8oxoG DNA complex (PDB ID: 1EBM [29]). The possible contribution of the “dipole effect” on 8-oxoG binding is unlikely to occur in OGG2 or AGOG in which the residue corresponding to Cys235 in hOGG1 is a histidine in OGG2 or a phenylalanine in AGOG. "
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    • "In a more recent structure of a catalytically active hOGG1/G@BULLETC–DNA complex that was crosslinked at a more remote location from the lesion (Ser292Cys), the target guanine was fully engaged inside the active site in a virtually identical position as 8oxoG in the LRC. In the IC, however, the guanine remained uncleaved, presumably because it lacks the N7 hydrogen present in 8oxoG that forms a specific hydrogen bond with the carbonyl of Gly42 [72]. The alignment of active site residues other than Gly42 are also important for catalysis, as observed in a phototrapped, uncleaved hOGG1/8oxoG–DNA complex that showed an intact 8oxoG–Gly42 interaction amidst a collection of "
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