Heavy ion effects on cells: survival of a temperature-conditional repair mutant of yeast

The temperature-conditional double-strand break repair mutant rad 54-3 of the yeast Saccharomyces cerevisiae was exposed to Ar, Ti and U ions with LET values between 900 and 15,000 keV/micron. Survival was assessed after incubation at the permissive (23 degrees C) and the restrictive temperature (36 degrees C) in aliquots of the same sample. Repair could be demonstrated in all instances, although to a somewhat reduced extent with the heavy ions as compared to X-rays. The results suggest that very densely ionizing radiations do not produce lesions which are irreparable per se, but that their ultimate fate depends on the particular repair system which may be different in different cell types.