DNA re-replication is susceptible to nucleotide level mutagenesis

ABSTRACT: The sources of genome instability, a hallmark of cancer, remain incompletely understood. One potential source is DNA re-replication, which arises when the mechanisms that prevent re-initiation of replication origins within a single cell cycle are compromised. Using the budding yeast Saccharomyces cerevisiae, we previously showed that DNA re-replication is extremely potent at inducing gross chromosomal alterations and that this arises in part because of the susceptibility of re-replication forks to break. Here, we examine the ability of DNA re-replication to induce nucleotide level mutations. During normal replication these mutations are restricted by three overlapping error avoidance mechanisms: the nucleotide selectivity of replicative polymerases, their proofreading activity, and mismatch repair. Using lys2InsEA14, a frameshift reporter that is poorly proofread, we show that re-replication induces up to a 30x higher rate of frameshift mutations and that this mutagenesis is due to passage of the re-replication fork, not secondary to re-replication fork breakage. Re-replication can also induce comparable rates of frameshift and base substitution mutations in a more general mutagenesis reporter CAN1, when the proofreading activity of DNA polymerase ε is inactivated. Finally, we show that the induction of lys2InsEA14 frameshift mutations by re-replication is dependent on mismatch repair. These results suggest that the mismatch repair associated with re-replication is attenuated, although at most sequences DNA polymerase proofreading provides enough error correction to mitigate the mutagenic consequences. Thus, re-replication can facilitate nucleotide level mutagenesis in addition to inducing gross chromosomal alterations, broadening its potential role in genome instability.

ORGANISM(S): Saccharomyces cerevisiae

PROVIDER: GSE124382 | GEO | 2018/12/27

REPOSITORIES: GEO