The use of plasmid DNA to probe DNA repair functions in the yeast Saccharomyces cerevisiae

✍ Scribed by White, Charles I. ;Sedgwick, Steven G.

• Publisher: Springer
• Year: 1985
• Tongue: English
• Weight: 823 KB
• Volume: 201
• Category: Article
• ISSN: 0026-8925
• DOI: 10.1007/bf00397993

✦ Synopsis

The survival of plasmid YRpl2 treated in vitro with ultraviolet-or 7-radiation, or with restriction endonucleases, has been used to investigate in vivo RAD gene activity in Saccharomyces cerevisiae. Yields of pyrmidine dimers or single and double strand breaks in plasmid DNA were assayed by physical methods. The biological effects of these damages were assayed by transformation of wildtype cells and rad mutants from each of the major groups of radiosensitive mutants. After UV-irradiation plasmid survival depended qualitatively on the same host functions that are needed for cellular survival. After 7-irradiation no such correspondence was found. Apart from a RAD52-dependent stimulation of transformation efficiency at low doses, other host repair functions had little effect. Stimulation of transformation corresponded with the production of double-but not single-strand breaks in plasmid sequences homologous with the yeast genome and may be linked with a transient increase in mitotic stability.

More generally these data also show that transformation events using the LiC1 protocol may entail the uptake of a very low number of plasmid molecules per cell over a 10-fold range of DNA concentrations.