Studies on the genetic regulation of cytochrome P-450 production in Saccharomyces cerevisiae.

An initial survey of 18 haploid strains of Saccharomyces cerevisiae revealed that only 3 of these strains could produce a detectable level of cytochrome P-450. A cross between a cytochrome P-450 producing strain of S. cerevisiae (B/B) and a non-producing strain (D22) gave a diploid which was a non-producer and a 2:2 segregation of producers to non-producers in meiotic tetrads. Of the two producers in each tetrad, one produced a higher level of cytochrome P-450 than the other. We deduce that cytochrome P-450 production in S. cerevisiae is regulated by a single nuclear gene and that a modifier gene is also involved which can enhance the amount of cytochrome P-450 synthesized. Benzo(a)pyrene (an inducer of P-450 in yeast) had no effect on the action of the regulatory gene.