ATR homolog Mec1 controls association of DNA polymerase ζ-Rev1 complex with regions near a double-strand break

DNA polymerase zeta (Pol zeta) and Rev1 contribute to the bypassing of DNA lesions, termed translesion DNA synthesis (TLS) [1-3]. Pol zeta consists of two subunits, one encoded by REV3 (the catalytic subunit) and the other encoded by REV7. Rev1 acts as a deoxycytidyl transferase, inserting dCMP opposite lesions. Pol zeta and Rev1 have been shown to operate in the same TLS pathway in the budding yeast Saccharomyces cerevisiae [2, 3]. Here, we. show that budding yeast Pol zeta and Rev1 form a complex and associate together with double-strand breaks (DSBs). As a component of the Pol zeta-Rev1 complex, Rev1 plays a noncatalytic role in the association with DSBs. In budding yeast, the ATR-homolog Mec1 plays a central role in the DNA-damage checkpoint response [4, 5]. We further show that Mec1-dependent phosphorylation promotes the Pol zeta-Rev1 association with DSBs. Rev1 association with DSBs requires neither the function of the Rad24 checkpoint-clamp loader [5] nor the Rad6-Rad18-mediated ubiquitination of PCNA [3]. Our results reveal a novel role of Mec1 in the localization of the Pol zeta-Rev1 complex to DNA lesions and highlight a linkage of TLS polymerases to the checkpoint response.