Function of the Plant DNA Polymerase Epsilon in Replicative Stress Sensing, a Genetic Analysis

Faithful transmission of the genetic information is essential in all living organisms. DNA replication is therefore a critical step of cell proliferation, because of the potential occurrence of replication errors or DNA damage when progression of a replication fork is hampered causing replicative stress. Like other types of DNA damage, replicative stress activates the DNA damage response, a signaling cascade allowing cell cycle arrest and repair of lesions. The replicative DNA polymerase epsilon (Pol epsilon) was shown to activate the S-phase checkpoint in yeast in response to replicative stress, but whether this mechanism functions in multicellular eukaryotes remains unclear. Here, we explored the genetic interaction between Pol epsilon and the main elements of the DNA damage response in Arabidopsis ( Arabidopsis thaliana). We found that mutations affecting the polymerase domain of Pol epsilon trigger ATR-dependent signaling leading to SOG1 activation, WEE1-dependent cell cycle inhibition, and tolerance to replicative stress induced by hydroxyurea, but result in enhanced sensitivity to a wide range of DNA damaging agents. Using knock-down lines, we also provide evidence for the direct role of Pol epsilon in replicative stress sensing. Together, our results demonstrate that the role of Pol epsilon in replicative stress sensing is conserved in plants, and provide, to our knowledge, the first genetic dissection of the downstream signaling events in a multicellular eukaryote.