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Gene Review

GAL3  -  transcriptional regulator GAL3

Saccharomyces cerevisiae S288c

Synonyms: Protein GAL3, YD8119.14, YDR009W
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Disease relevance of GAL3

  • By recruiting a dedicated signal transducer, GAL3, S. cerevisiae GAL switch has evolved to overcome the fortuitous induction, which occurs due to low signal to noise ratio in certain mutants of Escherichia coli and Kluveromyces lactis [1].

High impact information on GAL3

  • The yeast genetic network regulating galactose metabolism involves two proteins, Gal3p and Gal80p, that feed back positively and negatively, respectively, on GAL gene expression [2].
  • These results indicate that galactose-triggered Gal3p-Gal80p association in the cytoplasm activates Gal4p in the nucleus [3].
  • We also show that GAL gene expression can be activated by heterologous protein-protein interaction in the cytoplasm that is independent of galactose and Gal3p function [3].
  • Remarkably, the insertion of just two amino acids from Gal1p into the corresponding region of Gal3p confers galactokinase activity onto the resultant protein [4].
  • The transcriptional induction of the GAL genes of Saccharomyces cerevisiae occurs when galactose and ATP interact with Gal3p [4].

Biological context of GAL3


Associations of GAL3 with chemical compounds


Physical interactions of GAL3

  • How GAL3 and galactose activate GAL4 is not understood, but the long-standing notion has been that a galactose derivative formed by catalytic activity of GAL3 is the inducer that interacts with GAL80 or the GAL80-GAL4 complex [12].

Enzymatic interactions of GAL3


Regulatory relationships of GAL3


Other interactions of GAL3

  • GAL3 gene expression is required for rapid GAL4-mediated galactose induction of the galactose-melibiose regulon genes in Saccharomyces cerevisiae [5].
  • SRB10 and GAL3 are shown to represent parallel mechanisms for GAL gene induction [6].
  • Growth of gal7, gal10 and gal3 also exhibited reduced fitness in galactose medium [14].
  • When both GAL80 and GAL3 were overexpressed, the amount of coprecipitated Gal80p was not affected by galactose [7].
  • In experiments in which the presence of either the plasmid-carried cloned GAL3 gene or the plasmid-carried cloned GAL1-10-7 genes allows MEL1 induction of a gal3 gal1 gal7 cell, we find that loss of the plasmid results in the shutoff of MEL1 expression even when galactose is continuously present [9].

Analytical, diagnostic and therapeutic context of GAL3


  1. Stochastic variation in the concentration of a repressor activates GAL genetic switch: implications in evolution of regulatory network. Bhat, P.J., Venkatesh, K.V. FEBS Lett. (2005) [Pubmed]
  2. Dual feedback loops in the GAL regulon suppress cellular heterogeneity in yeast. Ramsey, S.A., Smith, J.J., Orrell, D., Marelli, M., Petersen, T.W., de Atauri, P., Bolouri, H., Aitchison, J.D. Nat. Genet. (2006) [Pubmed]
  3. Gene activation by interaction of an inhibitor with a cytoplasmic signaling protein. Peng, G., Hopper, J.E. Proc. Natl. Acad. Sci. U.S.A. (2002) [Pubmed]
  4. The insertion of two amino acids into a transcriptional inducer converts it into a galactokinase. Platt, A., Ross, H.C., Hankin, S., Reece, R.J. Proc. Natl. Acad. Sci. U.S.A. (2000) [Pubmed]
  5. Yeast regulatory gene GAL3: carbon regulation; UASGal elements in common with GAL1, GAL2, GAL7, GAL10, GAL80, and MEL1; encoded protein strikingly similar to yeast and Escherichia coli galactokinases. Bajwa, W., Torchia, T.E., Hopper, J.E. Mol. Cell. Biol. (1988) [Pubmed]
  6. Multiple signals regulate GAL transcription in yeast. Rohde, J.R., Trinh, J., Sadowski, I. Mol. Cell. Biol. (2000) [Pubmed]
  7. Analysis of the galactose signal transduction pathway in Saccharomyces cerevisiae: interaction between Gal3p and Gal80p. Suzuki-Fujimoto, T., Fukuma, M., Yano, K.I., Sakurai, H., Vonika, A., Johnston, S.A., Fukasawa, T. Mol. Cell. Biol. (1996) [Pubmed]
  8. The mechanism of inducer formation in gal3 mutants of the yeast galactose system is independent of normal galactose metabolism and mitochondrial respiratory function. Bhat, P.J., Hopper, J.E. Genetics (1991) [Pubmed]
  9. Genetic and molecular analysis of the GAL3 gene in the expression of the galactose/melibiose regulon of Saccharomyces cerevisiae. Torchia, T.E., Hopper, J.E. Genetics (1986) [Pubmed]
  10. Replacement of a conserved tyrosine by tryptophan in Gal3p of Saccharomyces cerevisiae reduces constitutive activity: implications for signal transduction in the GAL regulon. Lakshminarasimhan, A., Bhat, P.J. Mol. Genet. Genomics (2005) [Pubmed]
  11. Novel Gal3 proteins showing altered Gal80p binding cause constitutive transcription of Gal4p-activated genes in Saccharomyces cerevisiae. Blank, T.E., Woods, M.P., Lebo, C.M., Xin, P., Hopper, J.E. Mol. Cell. Biol. (1997) [Pubmed]
  12. Overproduction of the GAL1 or GAL3 protein causes galactose-independent activation of the GAL4 protein: evidence for a new model of induction for the yeast GAL/MEL regulon. Bhat, P.J., Hopper, J.E. Mol. Cell. Biol. (1992) [Pubmed]
  13. Analysis of the GAL3 signal transduction pathway activating GAL4 protein-dependent transcription in Saccharomyces cerevisiae. Bhat, P.J., Oh, D., Hopper, J.E. Genetics (1990) [Pubmed]
  14. Fluorescence based assay of GAL system in yeast Saccharomyces cerevisiae. Stagoj, M.N., Comino, A., Komel, R. FEMS Microbiol. Lett. (2005) [Pubmed]
  15. The Gal3p-Gal80p-Gal4p transcription switch of yeast: Gal3p destabilizes the Gal80p-Gal4p complex in response to galactose and ATP. Sil, A.K., Alam, S., Xin, P., Ma, L., Morgan, M., Lebo, C.M., Woods, M.P., Hopper, J.E. Mol. Cell. Biol. (1999) [Pubmed]
  16. Gal3p and Gal1p interact with the transcriptional repressor Gal80p to form a complex of 1:1 stoichiometry. Timson, D.J., Ross, H.C., Reece, R.J. Biochem. J. (2002) [Pubmed]
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