Nucleotide sequence and characterization of temperature-sensitive pol1 mutants of Saccharomyces cerevisiae.
We have analyzed the effects of temperature-sensitivity (ts)-conferring mutations in the Saccharomyces cerevisiae DNA polymerase I-encoding gene on cell growth, in vivo DNA synthesis, intrachromosomal gene conversion and pop-out recombination. Also, we have identified the molecular defect responsible for the ts phenotype. Two mutant alleles (cdc17-1, cdc17-2) were originally identified as cell-cycle mutations, while a third mutation (hpr3) was found during a genetic screening for mutants with a hyper-recombination phenotype. Both cdc17-2 and hpr3 cells complete one round of cell division and DNA replication after shift to nonpermissive temperature, before being arrested as dumbbell-shaped cells. Conversely, the cdc17-1 mutation immediately blocks growth and DNA synthesis at 37 degrees C. No substantial difference was observed in the frequency of intrachromosomal gene conversion and pop-out recombination events, when hpr3 and cdc17-1 were compared to the previously characterized pol1-1 mutant. These two frequencies were ten- to 30-fold above wild-type level at semipermissive temperature. In each mutant, a single bp substitution, causing the replacement of Gly residues by either Asp (cdc17-1, cdc17-2) or Glu (hpr3) in yeast DNA polymerase I is responsible for the ts phenotype.
Dipartimento di Genetica e Biologia dei Microrganismi, Università di Milano, Italy.
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G
Lucchini
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Muzi Falconi
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Pizzagalli
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Aguilera
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HL
Klein
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Plevani
D000595:Amino Acid Sequence; D002455:Cell Division; D004256:DNA Polymerase I / Q000235:genetics*; D004271:DNA, Fungal / Q000096:biosynthesis; D005656:Fungal Proteins / Q000235:genetics / Q000648:ultrastructure; D008938:Mitosis; D008969:Molecular Sequence Data; D009154:Mutation; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics*; D013696:Temperature
D004271:DNA, Fungal; D005656:Fungal Proteins; D004256:DNA Polymerase I