title: Repair of UV-irradiated plasmid DNA in a Saccharomyces cerevisiae rad3 mutant deficient in excision-repair of pyrimidine dimers.
abstract: The repair of UV-irradiated DNA of plasmid pBB29 was studied in an incision-defective rad3-2 strain of Saccharomyces cerevisiae and in a uvrA6 strain of Escherichia coli by the measurement of cell transformation. Plasmid pBB29 used in these experiments contained as markers the DNA of nuclear yeast gene LEU-2 and DNA of the bacterial plasmid pBR327 with resistance to Tet and Amp enabling simultaneous screening of transformant cells in both microorganisms. We found that the yeast rad3-2 mutant, deficient in incision of UV-induced pyrimidine dimers in nuclear DNA, was fully capable of repairing such lesions in plasmid DNA. The repair efficiency was comparable to that of the wild-type cells. The E. coli uvrA6 mutant, deficient in a specific nuclease for pyrimidine dimer excision from chromosomal DNA, was unable to repair UV-damaged plasmid DNA. The difference in repair capacity between the uvrA6 mutant strain and the wild-type strain was of several thousand-fold. It seems that the rad3 mutation, which confers deficiency in the DNA excision-repair system in yeast, is limited only to the nuclear DNA.
mesh_terms: D004260:DNA Repair; D004271:DNA, Fungal / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D004926:Escherichia coli / Q000235:genetics; D007700:Kinetics; D009154:Mutation; D010957:Plasmids / Q000528:radiation effects*; D011740:Pyrimidine Dimers / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development / Q000528:radiation effects; D014170:Transformation, Genetic; D014466:Ultraviolet Rays
chemical_list: D004271:DNA, Fungal; D011740:Pyrimidine Dimers