One of the main surprises from studies investigating the role of DNA polymerase eta in UV mutagenesis is the unexpected appearance of TG>TT mutations in both human XPV−/− mutated skin cancers and rad30∆ yeast.[32, 34] While this mutation class comprises 27% of all mutations in XPV−/− tumors, its underlying cause is still unclear. This evidence concerns the gene POLH and skin neoplasm.