The fifth essential DNA polymerase φ in Saccharomyces cerevisiae is localized to the nucleolus and plays an important role in synthesis of rRNA

摘要

We report that POL5 encodes the fifth essential DNA polymerase in Saccharomyces cerevisiae. Pol5p was identified and purified from yeast cell extracts and is an aphidicolin-sensitive DNA polymerase that is stimulated by yeast proliferating cell nuclear antigen (PCNA). Thus, we named Pol5p DNA polymerase φ. Temperature-sensitive pol5- 1～-3 mutants did not arrest at G2/M at the restrictive temperature. Furthermore, the polymerase active-site mutant POL5dn gene com- plements the lethality of Δpol5. These results suggest that the polymerase activity of Pol5p is not required for the in vivo function of Pol5p. rRNA synthesis was severely inhibited at the restrictive tem- perature in the temperature-sensitive pol5-3 mutant cells, suggesting that an essential function of Pol5p is rRNA synthesis.