Comparison of petite induction in yeast by acridines, ethidium and their photoaffinity probes.

The production of petite mutations by different acridine analogs was studied in Saccharomyces cerevisiae. Compounds with amino substituents at the 2 and 3 positions of the acridine nucleus and methylation at position 10 were effective for petite induction in growing cells but not in resting cells, while those with chloro, nitro and methoxy substituents were not effective in either resting or growing cells. Photosensitive azido derivatives of the acridines were tested to evaluate the role of covalent drug attachment for mutagenesis in resting cells. Photolysis of resting cells with 9-axido, 3-azido-6-amino-, 9-azido-10-methyl-, or 3-azido-6-amino-10-methyl-acridine was highly toxic. 3-Azido-6-amino-acridine, and especially 3-azido-10-methyl-, and 3-azido-6-amino-10-methyl-acridine, were effective petite inducers in resting cells. Thus, the photosensitive (azido) group at position 9 produced only cell killing while the azido group at position 3 and/or 6 led to effective petite induction in resting cells. In contrast, petite induction was observed only for growing cells, for dark control experiments with these compounds or with the monoazide precursor compounds.