A gene controlling inducibility of the galactose pathway enzymes in Saccharomyces

Population Analysis of the Deinduction Kinetics of Galactose Long-Term Adaptation Mutants of Yeast

“…3 The constant low fraction of positive cells observed in Phase II of Fig. 1 has been observed by previous workers who reported 5% of these colonies to be gal+ lines (9). We have observed that colonies transferred from EB+1 galactose plates in Phase II through glucose medium retain a typical gal 3 phenotype (data not shown).…”

“…The galactose long-term adaptation mutation (gal 3*) in Saccharomyces cerevisiae is characterized by a long lag period in galactose medium after which growth in galactose commences at a normal rate (9). Neither the function nor the nature of the Gal 3 gene product is known.…”

“…Neither the function nor the nature of the Gal 3 gene product is known. However, it is known that the combination of the gal 3 mutation and the respiratory-deficient petite (p -) mutation acts as a conditional lethal mutation with regard to growth on galactose (9). In this communication, we report the observation that gal 3, p+ strains adapted to galactose continue to grow on galactose when converted to p -strains by treatment with ethidium bromide, which specifically induces the respiratory petite mutation without attendant lethality (10 (12) or in YET broth medium (10 g of tryptone and 5 g of yeast extract per liter of medium).…”

Regulation of the galactose pathway in Saccharomyces cerevisiae : Induction of uridyl transferase mRNA and dependency on GAL4 gene function

“…The GAL4 locus probably codes for a polypeptide because some gal4 mutations are suppressible by unlinked nonsense suppressors (D. Hawthorne, personal communication). The expression of the GAL4 gene appears to be under the direct control of the tightly linked GAL81 region and indirectly under the control of the unlinked GAL80 gene (11,13,14). The GAL81 region is characterized by a mutation, GAL81 C (designated C by Douglas and Hawthorne), that results in constitutive production of the galactose pathway enzyme activities (11).…”

“…This constitutive phenotype is expressed only when the GAL81 c mutation occurs in a cis configuration with respect to a functional GAL4 gene (11). The GAL80 locus is defined by three allelic configurations: GAL80, inducible; gal80, constitutive; and GAL80S, noninducible (gal80 is recessive to GAL80 and GAL80S is dominant to GAL80) (13,14).…”