The Fifth Essential DNA Polymerase ϕ in Saccharomyces cerevisiae is Localized to the Nucleolus and Plays an Important Role in Synthesis of rRNA

• Published in: Proceedings of the National Academy of Sciences - PNAS 2002-07, Vol.99 (14), p.9133-9138
• Main Authors: Shimizu, Kikuo, Kawasaki, Yasuo, Hiraga, Shin-Ichiro, Tawaramoto, Maki, Nakashima, Naomi, Sugino, Akio
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Amino acids; Antibodies; Aphidicolin - pharmacology; Base Sequence; Binding Sites - genetics; Biochemistry; Biological Sciences; Cell cycle; Cell Division; Cell extracts; Cell growth; Cell Nucleolus - enzymology; DNA; DNA Replication; DNA, Fungal - genetics; DNA, Fungal - metabolism; DNA-Directed DNA Polymerase - genetics; DNA-Directed DNA Polymerase - isolation & purification; DNA-Directed DNA Polymerase - metabolism; Enhancer Elements, Genetic; Enzymes; Gels; Genes, Fungal; Molecular Sequence Data; Mutation; Ribonucleic acid; Ribosomal DNA; RNA; RNA, Fungal - biosynthesis; RNA, Fungal - genetics; RNA, Ribosomal - biosynthesis; RNA, Ribosomal - genetics; Saccharomyces cerevisiae - enzymology; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - metabolism; Temperature; Yeast; Yeasts
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.142277999

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 complements 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 temperature in the temperature-sensitive pol5-3 mutant cells, suggesting that an essential function of Pol5p is rRNA synthesis. Pol5p is localized exclusively to the nucleolus and binds near or at the enhancer region of rRNA-encoding DNA repeating units.