Human DNA polymerase ε is phosphorylated at serine-1940 after DNA damage and interacts with the iron-sulfur complex chaperones CIAO1 and MMS19.

We describe a dynamic phosphorylation on serine-1940 of the catalytic subunit of human Pol e, POLE1, following DNA damage. We also describe novel interactions between POLE1 and the iron-sulfur cluster assembly complex CIA proteins CIAO1 and MMS19. We show that serine-1940 is essential for the interaction between POLE1 and MMS19, but not POLE1 and CIAO1. No defect in either proliferation or survival was identified when POLE1 serine-1940 was mutated to alanine in human cells, even following treatment with DNA damaging agents. We conclude that serine-1940 phosphorylation and the interaction between serine-1940 and MMS19 are not essential functions in the C terminal domain of the catalytic subunit of DNA polymerase e.