Repair of DNA double-strand breaks requires two homologous DNA duplexes

Abstract

DNA repair and cell survival in haploid and its diploid derivative strains of Saccharomyces cerevisiae were studied after 100 krad X-ray irradiation. The cells were in the G1 stage of the cell cycle, where haploid cells had only one copy of genetic material per genome and diploid had two copies. It was found that diploid could repair double-strand breaks in its DNA after 48 hr of liquid holding which was accompanied by a four-fold rise in survival. In contrast a haploid strain failed to repair its DNA and showed no increase in survival after liquid holding. It is concluded that (1) repair of DNA double-strand breaks requires the availability of two homologous DNA duplexes, (2) restoration of cell viability during liquid holding is connected with repair of DNA double-strand breaks and (3) this repair is a slow process possibly associated with slow finding and conjugation of homologous chromosomes.

The delayed appearance of haploid and homozygous diploid Saccharomyces cerevisiae yeast cells of wild-type and radiosensitive mutants surviving after exposure to gamma rays and alpha particles

“…Bernstein, 2012; Luchnik et al, 1977) and nonhomologous DNA end joining (Lewis & Resnick, 2000;Mao, Bozzella, Seluanov, & Gorbunova, 2008). Unrepaired or misrepaired DNA double-strand break may result in both cell inactivation and genetic instability.…”

“…Several authors have investigated genome instability using Saccharomyces cerevisiae, a simple singlecelled organism model (McMurray & Goltschling, 2004;Sheltzer et al, 2011;Yuen et al, 2007). Repair of DNA DSB requires two homologous DNA duplexes and due to this ability diploid yeast cells are more resistant to ionizing radiation than haploids (Luchnik, Glaser, & Shestakov, 1977). Delayed appearance of colonies by cells surviving ionizing radiation exposure was more pronounced for diploid than for haploid yeast cells of wild-type (Korogodin et al, 2007).…”

Mutations in the Saccharomyces cerevisiae CDC1 gene affect double-strand-break-induced intrachromosomal recombination.

“…However, the finding that the cdcl-100 mutation CDCJ is an essential gene, it is likely that the affect of cdcl alters the spectrum of recombinants without affecting cell Substantial evidence suggests that DSB repair occurs by a recombinational mechanism (15,36). A large measure of support comes from the observation that homologous DNA is required for efficient DSB repair (9,15,39,48). The observation of mutations that affect both induced mitotic recombination and cell survival following DNA damage further enhances this notion (15,36).…”

“…An important aspect of this process is the recognition and repair of DNA lesions that arise during the course of normal cellular metabolism or from exposure to genotoxic agents in the environment. In the yeast Saccharomyces cerevisiae, toxicity of DNA double-strand breaks (DSBs) is dependent upon several factors, including ploidy (9, 15, 48), cell cycle position (6,39,49), and the genetic constitution of the cell (15, 36). Prior to DNA replication, haploid cells in the G1 phase are particularly sensitive to killing by ionizing radiation, indicating that DSBs are repaired by a DNA homology-dependent mechanism.…”

Manifestation of synergism under simultaneous action of hyperthermia and antitumor drugs on yeast cells

“…The earlier published experimental data on simultaneous action of chemical agent and of increase of temperature have been per formed predominantly on mammalian cells (Johnson, Pavelec, 1973;Hahn, 1979;Herman et al, 1982;Engelhardt, 1987;Eichholtz Wirth, Hietel, 1990;Urano et al, 1990;Pantyukhina, Petin, 1999). Most researchers ascribe mechanism of synergic interaction to inhibition of processes of recovery, which have been well studied in yeast cells at the molecular (Game, Cox, 1973;Luchnik et al, 1977;Saeki et al, 1980;Frankenberg Schwager et al, 1984) and cellular levels (Korogodin, 1966;Petin, 1987;Zhurakovskaya, Petin, 1988;Krasavin, 1989;Petin, Komarov, 1989).…”