Effects of post-treatment incubation on recombinogenesis in incision-proficient and incision-deficient strains of Saccharomyces cerevisiae: I. Recombinogenesis after UV- and gamma-ray-irradiation.
After UV-irradiation of G1 phase cells, most gene conversion and crossing-over took place in cells of incision-proficient strains without post-irradiation incubation. In contrast, incision-deficient cells markedly induced both of these recombinational events only after irradiated cells were incubated for several hours in liquid growth medium before selection. These results indicate that when G1 cells are irradiated with UV recombinational events are initiated during that G1 phase in incision-proficient strains; whereas, they are not initiated in irradiated incision-deficient strains before the cells reach the S/G2 phase. Experimental gamma-ray results also suggest that post-irradiation incubation is not required for incision-proficient and -deficient strains to initiate mitotic recombinational events. Taken together, these results show that the formation of incision nicks and of post-replication gaps in DNA appears to be necessary for the initiation of recombinational events after UV treatment; whereas, it is not required after gamma-irradiation.
Saeki
T
T
Division of Genetics, National Institute of Radiological Sciences, Chiba, Japan.
Machida
I
I
D005720:Gamma Rays; D007399:Interphase; D011831:Radiation Genetics; D011995:Recombination, Genetic / Q000528:radiation effects*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000528:radiation effects*; D014466:Ultraviolet Rays