Translesion DNA synthesis and damage tolerance pathways

Abstract

One of the critical cellular effects of DNA damage is the impediment of the activity of high-fidelity DNA polymerases for replication. Although DNA repair mechanisms physically remove DNA damage before the initiation of DNA replication, remaining damage DNA can still persist in S phase and inhibit replicative DNA polymerases. To deal with this, cells have developed mechanisms to copy chromosomes with unrepaired DNA damage, known as DNA damage tolerance (DDT) mechanisms. As a consequence of DDT, cells can complete chromosomal duplication even in the presence of low levels of DNA damage. DDT mechanisms have been classified into two pathways: translesion DNA synthesis (TLS) and homology-directed repair. In TLS, specialized TLS DNA polymerases utilize damaged DNA as the template and extend the 3′ end of the stalled primer beyond the damage. In homology-directed repair, the stalled primer anneals with the newly synthesized daughter strand and transiently utilizes the undamaged complementary sequence as a template for DNA synthesis. In this article, we summarize and discuss the molecular mechanisms of the DDT pathways of well-analyzed organisms: Escherichia coli, the budding yeast Saccharomyces cerevisiae, and mammalians.