After REV1 inserts a nucleotide directly opposite the template lesion, translesion synthesis (TLS) is continued by DNA polymerase zeta (POLZ), a complex of REV3L and MAD2L2 (REV3 and REV7 in yeast) (Nelson et al. 1996a, Neal et al. 2010). POLZ is a poorly processive enzyme in both yeast and humans and usually incorporates less than 30 nucleotides before it dissociates from the template. In human cells, the processivity of POLZ is increased in the presence of DNA polymerase delta (POLD) subunits POLD2 and POLD3, which act as accessory subunits for POLZ (Nelson et al. 1996b, Lee et al. 2014). POLZ is error-prone, especially in the context of TLS across AP (apurinic/apyrimidinic) sites, resulting in incorporation of mispaired dNTPs, which contributes to TLS-related mutagenesis (Shachar et al. 2009, Lee et al. 2014).