Contiguous 2,2,4-triamino-5(2H)-oxazolone obstructs DNA synthesis by DNA polymerases alpha, beta, eta, iota, kappa, REV1 and Klenow Fragment exo(-), but not by DNA polymerase zeta

摘要

Guanine is the most easily oxidized of the four DNA bases, and contiguous guanines (GG) in a sequence are more readily oxidized than a single guanine in a sequence. Continued oxidation of GGs results in a contiguous oxidized guanine lesion. Two contiguous 2,5-diamino-4H-imidazol-4-ones, an oxidized form of guanine that hydrolyses to 2,2,4-triamino-5(2H)-oxazolone (Oz), are detected following the oxidation of GG. In this study, we analysed translesion synthesis (TLS) across two contiguous Oz molecules (OzOz) using Klenow Fragment exo(-) (KF exo(-)) and DNA polymerases (Pols) alpha, beta, zeta, eta, iota, kappa and REV1. We found that KF exo(-) and Pols alpha, beta, iota and REV1 inserted one nucleotide opposite the 3' Oz of OzOz and stalled at the subsequent extension, and that Pol kappa incorporated no nucleotide. Pol eta only inefficiently elongated the primer up to full-length across OzOz; the synthesis of most DNA strands stalled at the 3' or 5' Oz of OzOz. Surprisingly, however, Pol zeta efficiently extended the primer up to full-length across OzOz, unlike the other DNA polymerases, but catalysed error-prone nucleotide incorporation. We therefore believe that Pol zeta is required for efficient TLS of OzOz. These results show that OzOz obstructs DNA synthesis by DNA polymerases except Pol zeta.