REV3L and Xeroderma pigmentosum variant: As all these polymerases have been confirmed to bypass DNA damage, with functions similar to those of pol η, it may be deduced that the genes REV3L, POLK, POLI and POLQ, encoding pol ζ, κ, ι and θ, respectively, may also have altered expression and contribute to mutagenesis in XP-V tumors.