DNA Repair Synthesis during Base Excision Repair in Vitro Is Catalyzed by DNA Polymerase ε and Is Influenced by DNA Polymerases α and δ in Saccharomyces cerevisiae

Base excision repair is an important mechanism for correcting DNA damage produced by many physical and chemical agents. We have examined the effects of the REV3 gene and the DNA polymerase genes POL1, POL2, and POL3 of Saccharomyces cerevisiae on DNA repair synthesis in nuclear extracts. Deletional inactivation of REV3 did not affect repair synthesis in the base excision repair pathway. Repair synthesis in nuclear extracts of pol1, pol2, and pol3 temperature-sensitive mutants was normal at permissive temperatures. However, repair synthesis in pol2 nuclear extracts was defective at the restrictive temperature of 37°C and could be complemented by the addition of purified yeast DNA polymerase ε. Repair synthesis in pol1 nuclear extracts was proficient at the restrictive temperature unless DNA polymerase on was inactivated prior to the initiation of DNA repair. Thermal inactivation of DNA polymerase δ in pol3 nuclear extracts enhanced DNA repair synthesis ∼2-fold, an effect which could be specifically reversed by the addition of purified yeast DNA polymerase δ to the extract. These results demonstrate that DNA repair synthesis in the yeast base excision repair pathway is catalyzed by DNA polymerase ε but is apparently modulated by the presence of DNA polymerases α and δ.