title: Temperature-sensitive mutations in the yeast DNA polymerase I gene.
abstract: Seven mutations that yield thermolabile DNA polymerases have been isolated in the DNA polymerase I gene, POL1, of Saccharomyces cerevisiae. Strains carrying the mutant genes are temperature sensitive for growth. The pol1 mutants were identified by a method that has general applicability for identification of both temperature-sensitive and null mutations. A plasmid containing a mutagenized pol1 gene was transformed into a strain in which the only functional copy of the POL1 gene was carried on an unstable plasmid. The genes conferring temperature-sensitive growth were detected after elimination of the unstable plasmid containing the wild-type gene. DNA polymerase I isolated from each of the mutants is defective at both 23 degrees C and 36 degrees C. DNA synthesis is deficient in vivo at 36 degrees C in all the mutants, while RNA synthesis is normal in all but one of the mutants. The terminal phenotype of pol1 temperature-sensitive mutants is dumbbell-shaped cells in which the nucleus has migrated to, but apparently not entered, the isthmus separating the mother and the daughter. The POL1 gene is located on chromosome XIV approximately 2 centimorgans away from met4.
mesh_terms: D004256:DNA Polymerase I / Q000235:genetics*; D004261:DNA Replication; D005796:Genes; D005800:Genes, Fungal; D009154:Mutation; D010957:Plasmids; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D013696:Temperature; D014158:Transcription, Genetic
chemical_list: D004256:DNA Polymerase I