GAL11 Protein, an Auxiliary Transcription Activator for Genes Encoding Galactose-Metabolizing Enzymes in Saccharomyces cerevisiae

Abstract

Normal function of the GAL11 gene is required for maximum production of the enzymes encoded by GAL1, GAL7, and GAL10 (collectively termed GAL1,7,10) in Saccharomyces cerevisiae. Strains bearing a gal11 mutation synthesize these enzymes at 10 to 30% of the wild-type level in the induced state. In a DNA-RNA hybridization experiment, the gal11 effect was shown to be exerted at the transcription level. Yeast cells bearing the gal11 mutation were shown to grow on glycerol plus lactate more slowly than the wild type. We isolated recombinant plasmids carrying the GAL11 gene by complementation of the gal11 mutation. When the GAL11 locus was disrupted by insertion of the URA3 gene, the resulting yeast cells (gal11::URA3) exhibited phenotypes almost identical to those of the gal11 strains, with respect to both galactose utilization and growth on nonfermentable carbon sources. Deficiency of Gal4, the major transcription activator for GAL1,7,10, was epistatic over the gal11 defect. The Gal11 deficiency lowered the expression of GAL2 but not that of MEL1 or GAL80; expression of these genes is also known to be dependent on GAL4 function. We determined the nucleotide sequence of GAL11, which is predicted to encode a 107-kilodalton protein with stretches of polyglutamine and poly(glutamine-alanine). An alpha-helix-beta-turn-alpha-helix structure was found in a distal part of the predicted amino acid sequence. A possible role of the GAL11 product in the regulation of galactose-inducible genes is discussed.

Changes in the Protein Expression of Yeast as a Function of Carbon Source

“…GAL6 (also known as LAP3), an aminopeptidase, has been shown to be upregulated at the protein level in response to galactose, and the same trend was observed in our data (ratio = 1.4, p-value = 0.1109). The transcription factor GAL11, which showed only a minor change in our experiments (ratio = 1.2, p-value = 0.2122), is known to regulate the production of GAL1, GAL7, and GAL10 . The protein GAL83, a protein believed to complex with SNF1 and thereby modulate the intracellular transport of SNF1, was observed in the proteomics experiments to be downregulated on galactose (ratio = 0.5, p-value = 0.1835).…”

“…The transcription factor GAL11, which showed only a minor change in our experiments (ratio ) 1.2, p-value ) 0.2122), is known to regulate the production of GAL1, GAL7, and GAL10. 36 The protein GAL83, a protein believed to complex with SNF1 and thereby modulate the intracellular transport of SNF1, 37 was observed in the proteomics experiments to be downregulated on galactose (ratio ) 0.5, p-value ) 0.1835). SNF1 (ratio ) 1.2, p-value ) 0.4319) showed almost no change in our experiments, though the measurement was not statistically significant.…”

Evidence That Gal11 Protein Is a Target of the Gal4 Activation Domain in the Mediator

“…However, several lines of evidence, some emerging from this study, indicate that while Gal4 AD-Gal11 binding is critical for efficient activator-mediator binding, it is unlikely to be the whole story. It has been known for some time that deletion of GAL11 reduces, but does not abolish, Gal4mediated transcription (34). The level of GAL gene expression is approximately 10%-15% in a ∆gal11 strain of that observed in a wild-type strain.…”

A multiplicity of mediators: alternative forms of transcription complexes communicate with transcriptional regulators

“…With the addition of the missing GTFs the holoenzyme is competent for communication with a model transcriptional activator, GAL4-VP16, in vitro (27,37). In addition, some of the Srbps (35), Gal11p (38,39), Sin4p, Rgr1p (31) and Rox3p (40) were initially identified as gene regulatory factors. Furthermore, tethering Gal11p or Srb5p to DNA via a DNA binding domain is sufficient for activation in vivo (29,41).…”

“…The two holoenzyme complexes are portrayed transcribing overlapping major and minor subsets of genes. This model is based on the fact that some of the SRBs are essential genes shown to affect transcription of most yeast genes (47), while PAF1, CDC73, CCR4 and HPR1, in addition to the shared components GAL11, SIN4 and RGR1, are all non-essential and appear to affect only a subset of transcripts (31,39,43,45,46). The overlapping nature of the effects of the two complexes is based on the fact that expression of some genes is affected by mutations in either complex.…”