Light-illumination effects on the cellular concentration of photolyase molecules in yeast.

The effects of light-illumination in the absence or presence of cycloheximide (CHX) on the number of photoreactivating enzyme molecules per haploid cell of Saccharomyces cerevisiae (NPRE) were investigated. NPRE increased, when the cells were held in buffer in light in the absence of CHX for 24 or 48 h before UV-irradiation (buffer-holding). The increase of NPRE was clearly observed in cells, whose NPRE before bufferholding was small, that is, in stationary growth phase cells grown at 37 degrees C and in logarithmic growing cells incubated at 30 degrees C. In the case of buffer-holding in light in the presence of CHX or in the dark in the absence or presence of CHX, the increase of NPRE was small or not observed.