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.

REPAIR OF UV‐IRRADIATED PLASMID DNA IN EXCISION REPAIR DEFICIENT MUTANTS OF Saccharomyces cerevisiae

“…In another possibility, we suggest that R A D l , 2 , 3 and 4 gene functions are required for internal enzyme transport from cytoplasm to nucleus for excision repair. These results are supported by recent similar experiments about rad3 mutant (Dominski and Jachymczyk, 1984). We consider R A D 1 , 2 , 3 and 4 gene products are probably not components of UV-specific endonuclease.…”

REPAIR OF UV‐DAMAGED INCOMING PLASMID DNA IN Saccharomyces cerevisiae

“…It is interesting to note here that identical results were obtained by other laboratories with radl-1 mutants and UV-incoming DNA (White and Sedgwick, 1985;Dominski and Jachymczyk, 1987). However, Ikai et al (1985) reported that the radl-2 mutant had a normal capacity to repair UVincoming DNA although the mutant was sensitive to UV.…”

“…the plasmid survival was different from that found in the RAD+ host. The mutants rad2-6 (Ikai et al, 1985) and rad2 (Dominski and Jachymczyk, 1987) were able to repair UV-incoming DNA as well as the parental RA D + strains. Although different plasmid DNAs, transformation procedures and other experimental conditions were used, the differences between alleles should be further investigated.…”

Deoxyribonucleic acid repair in the yeast Saccharomyces cerevisiae.

“…They noted that, relative to a wild-type strain, transforma-tion was unaffected in the rad3-2 strain and also in radl-2, rad2-6, and rad44 strains. However, as in the study by Dominski and Jachymczyk (41), in E. coli uvrA the transformation frequency was dramatically reduced relative to that of a uvrA+ strain.…”