DNA polymerase eta mostly catalyzes an error-free bypass of the most frequent UV lesions, pyrimidine dimers of the cyclobutane-type. In addition to its nuclear localization, we show here for the first time its mitochondrial localization in budding yeast. In mitochondria, this polymerase improves bypass replication fidelity opposite UV damage as shown in base pair substitution and frameshift assays. For base pair substitutions, polymerase eta appears to be related in function and epistatic to DNA polymerase zeta which, however, plays the opposite role in the nucleus. (C) 2013 Elsevier Inc. All rights reserved.