In Vivo Bypass of 8-oxodG

8-oxog is one of the most common and mutagenic dna base lesions caused by oxidative damage. however,it has not been possible to study the replication of a known 8-oxog base in vivo in order to determine the accuracy of its replication,the influence of various components on that accuracy,and the extent to which an 8-oxog might present a barrier to replication. we have been able to place a single 8-oxog into the saccharomyces cerevisiae chromosome in a defined location using single-strand oligonucleotide transformation and to study its replication in a fully normal chromosome context. during replication,8-oxog is recognized as a lesion and triggers a switch to translesion synthesis by pol η,which replicates 8-oxog with an accuracy (insertion of a c opposite the 8-oxog) of approximately 94%. in the absence of pol η,template switching to the newly synthesized sister chromatid is observed at least one third of the time; replication of the 8-oxog in the absence of pol η is less than 40% accurate. the mismatch repair (mmr) system plays an important role in 8-oxog replication. template switching is blocked by mmr and replication accuracy even in the absence of pol η is approximately 95% when mmr is active. these findings indicate that in light of the overlapping mechanisms by which errors in 8-oxog replication can be avoided in the cell,the mutagenic threat of 8-oxog is due more to its abundance than the effect of a single lesion. in addition,the methods used here should be applicable to the study of any lesion that can be stably incorporated into synthetic oligonucleotides. © 2013 rodriguez et al.