Crystal Structure of a Replicative DNA Polymerase Bound to the Oxidized Guanine Lesion Guanidinohydantoin

The oxidation of guanine generates one of the most common DNA lesions. 8-oxo-7,8-dihydroguanine (8-oxoG). The further oxidation of 8-oxoG can produce either guanidinohydantoin (Gh) In duplex DNA or spirominodihydantoin (Sp) In nucleosides and ssDNA. Although Gh can be a Strong block for replicative DNA polymerases such as RB69 DNA polymerase, thiis lesion IS also mutagenic: DNA polymerases bypass Gh by preferentially incorporatting, a with a Slight preference Cor ad I results Ili G - C - T - A or G - C - C - G trailsvcrsions. The 2.15 A crystal structure of the replicative R 1369 DNA polymerase in complex with DNA containing major groove. In this conformation Gh is no longer ill position to serve as a templating base for the Incorporation of an incoming nucleotide. This work also constitutes the first crystallographic structure of Gh, which is stabilized in file R configuration in the two polymerase/DNA complexes present ill file crystal asymmetric unit. In contrast to 8-oxoG, Gh is found in a high syn conformation in the DNA duplex and therefore presents the same hydrogen bond donor and acceptor pattern as thymine, which explains the propensity of DNA polyrnerases to incorporate a purine opposite Gh when bypass Occurs.