The effect of DNA structure on the catalytic efficiency and fidelity of human DNA polymerase beta on templates with platinum-DNA adducts

DNA adducts formed by platinum-based anticancer drugs interfere with DNA re plication. The carrier ligand of the platinum compound is likely to affect the conformation of the Pt DNA adducts. In addition, the conformation of th e adduct can also change upon binding of damaged DNA to the active site of DNA polymerase. From the crystal structures of pol P ternary complexes it i s evident that undamaged gapped and primed single-stranded (non-gapped) DNA templates exist in very different conformations when bound to pol beta. Th erefore, one might expect that the constraints imposed on the damaged templ ates by binding to the polymerase active site should also affect the confor mation of the Pt-DNA adducts and their ability to inhibit DNA replication. In support of this hypothesis we have found that the efficiency, carrier li gand specificity, site of discrimination (3 ' -G: versus 5 ' -G of the Pt-G G adducts), and fidelity of translesion synthesis past Pt-DNA adducts by po l beta are strongly affected by the structure of the DNA template. Previous studies have suggested that the conformation of Pt-DNA adducts may be affe cted by the sequence context of the adduct, In support of this hypothesis, our data show that sequence context affects the efficiency, fidelity, and p attern of misincorporation by pol beta.