Glucose-induced regulatory defects in the Saccharomyces cerevisiae byp1 growth initiation mutant and identification of MIG1 as a partial suppressor

Abstract

Saccharomyces cerevisiae bypl-3 mutants displayed a long lag phase when shifted from a nonfermentable carbon source to a medium containing glucose. The bypl-3 mutation also caused several defects in regulatory phenomena which occur during the transition from the derepressed state to the repressed state. As opposed to wild-type cells, the addition of glucose to cells of the bypl-3 mutant grown on nonfermentable carbon sources did not induce a cyclic AMP signal. Fructose-2,6-bisphosphate formation and inactivation of fructose-1,6-bisphosphatase were severely delayed, but trehalase activation was not affected. In addition, the induction of pyruvate decarboxylase both at the level of activity and that of transcription was very slow compared with that in wild-type cells. These pleiotropic defects in glucose-induced regulatory phenomena might be responsible for the very long lag phase of bypl-3 cells and the inability of ascospores to initiate growth after germination on glucose media. Screening of a yeast gene library for clones complementing the bypl-3 phenotype resulted in the isolation of a truncated form of the previously described zinc finger transcription repressor MIGi. The entire MIG) gene and the truncated form suppressed even on a single-copy vector the growth initiation defect but not the regulatory abnormalities of the bypl-3 mutant. MIG) is not allelic to bypl-3.The addition of glucose to derepressed cells of the yeast Saccharomyces cerevisiae causes a series of rapid changes in enzyme activity due to posttranslational modification (12, 20) followed by slower changes which are due to repression (6) or induction (e.g., reference 17) at the transcriptional level. Identification of the glucose-induced signaling pathways triggering these events has attracted a lot of attention. Evidence has been obtained that cyclic AMP (cAMP)-dependent protein phosphorylation is involved in rapid inactivation of fructose-1,6-bisphosphatase, isocitrate lyase, and the galactose and high-affinity glucose carrier and in rapid activation of trehalase and phosphofructokinase 2 (22). The addition of glucose to derepressed yeast cells causes a rapid signal-like spike in the cAMP level (21). Incubation of temperature sensitive mutants in cAMP synthesis at the restrictive temperature or cAMP-requiring mutants in the absence of cAMP abolishes the glucose-induced cAMP signal and also the inactivation of fructose-1,6-bisphosphatase (27) and the activation of trehalase and phosphofructokinase 2 (7). This has been taken as evidence that the glucose-induced cAMP signal triggers phosphorylation of the enzymes by causing activation of cAMP-dependent protein kinase. Under these conditions, however, not only is the cAMP signal abolished, but the basal cAMP level in the cells is also much lower than that in wild-type cells. It has never been investigated whether the absence of the cAMP * Corresponding author. monophosphates and sedoheptulose-7-phosphate, a metabolite of the pentosephosphate pathway, accumulate at unusually high levels (4). Howe...

Isolation of the MIG1 Gene from Candida albicans and Effects of Its Disruption on Catabolite Repression

“…1A). The similarity of sequence and the fact that a truncated version of ScMIG1 in single copy or, more efficiently, in multicopy suppresses the phenotype of a byp1-3 mutant, an allelic form of TPS1, in S. cerevisiae (22) made it likely that the cloned gene was the MIG1 gene from C. albicans. The nucleotide sequence revealed an ORF encoding a putative protein of 574 amino acids with a calculated molecular mass of 63 kDa.…”

Isolation and molecular characterization of the Arabidopsis TPS1 gene, encoding trehalose‐6‐phosphate synthase

“…Complementation of the tps1 mutant growth phenotype ( Figure 1a) does not prove by itself that the cloned gene encodes a trehalose-6-P synthase. In fact, extragenic suppressors of tps1 have been isolated that partially rescue the growth defect only, not other defects associated with the mutation (Blá zquez and Gancedo, 1995;Hohmann et al, 1992). Two results argue against pATT9-1 encoding a sup- .…”

Composition and Functional Analysis of the Saccharomyces cerevisiae Trehalose Synthase Complex

“…The TPS1/TSS1 gene has also been cloned independently by complementation of the cif1 mutant (9) and the fdp1 and byp1 mutants (10, 11). In the latter case, we called it GGS1 for "component of a general glucose sensing system" since these mutants were unable to grow on glucose and were deficient in a wide range of glucose-induced regulatory phenomena (10,(12)(13)(14).…”