Consititutive expression of the maltose fermentation enzymes in Saccharomyces cerevisiae is dependent upon the mutational activation of a non-essential homolog of MAL63 (original) (raw)
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Proceedings of the National Academy of Sciences, 1984
The MAL6 locus is one of five closely related unlinked loci, any one of which is sufficient for fermentation of maltose in Saccharomyces. Previous genetic analysis indicated that this locus is defined by two complementation groups, MALp and MALg. MALp reportedly is a regulatory gene required for inducible synthesis of the two enzymatic functions needed for fermentation: maltose permease and maltase. We have investigated the physical and genetic structure of the MAL6 locus, which has been isolated on a recombinant DNA plasmid. One subclone of the region, pDF-1, was found to encode a single transcribed region and to contain the MALp gene. A second subclone, pl, was shown to contain the MALg function but surprisingly had not one but two maltose-inducible transcripts. Subclones having only one of these transcribed regions lacked MALg activity. The three transcribed regions have been named MAL61 and MAL62, which correspond to MALg, and MAL63, which corresponds to MALp. This clustered arrangement of a regulatory gene adjacent to the sequences it controls has not previously been described in eukaryotes and is reminiscent of bacterial operons except that the messenger RNA molecules are not polycistronic.
MAL63 codes for a positive regulator of maltose fermentation in Saccharomyces cerevisiae
Current Genetics, 1988
Genetic analysis of the MAL6 locus has previously yielded mal6 mutants which fall into a single complementation group and which are noninducibte for maltase and maltose permease. However, the strains used in these studies contained additional partially functional copies of MALl (referred to as MALlg) and MAL3 (referred to as MAL3g). Using a strain lacking MALg genes, we have isolated two classes of mutants and these classes correspond to mutations in MAL63 and MAL61, two genes of the MAL6 complex. Disruptions of MAL63 are noninducible for maltase and maltose permease and for their corresponding mRNAs. The real6 mutants are shown to map to MAL63. Inducer exclusion as a cause of the noninducible phenotype of the real63 mutations has been eliminated by constructing a ma163 mutant in a strain constitutive for maltose permease; the strain remains noninducible. These results rigorously demonstrate that MAL63 is a regulatory gene which plays a positive role in the regulation of maltose fermentation.
Journal of Bacteriology
Saccharomyces yeast strains able to ferment maltose carty at least one member of a family of MAL loci: MAL], MAL2, MAL3, MAL4, and MAL6. The MAL6 locus has been cloned and shown to be a cluster of at least three transcribed regions, all of which are required for maltose fermentation. Transcription at two of these genes, MAL61 and MAL62, is both induced by maltose and repressed by glucose. The third gene, MAL63, appears to encode a regulatory product controlling mnaltose fermentation. In this report, we demonstrate that the MAL62 gene is the structural gene coding for the enzyme maltase. Strain 332-5A is a maltose fermenter of the genotype MAL6 mad)0. Integrative disruption of the MAL62 gene of the MAL6 locus produces a strain which is still capable of fermenting maltose, but which synthesizes a more heat-labile form of maltase than the undisrupted strain. Synthesis of this more heat-labile maltase was shown to be linked to the mall°locus present in the strain. Integrative disruption of both the MAL62 gene and the MAL62-homologous sequence present at the mall°locus produces a nonfermenter which is unable to synthesize maltase. These results identify MAL62 as the maltase structural gene.
Molecular and cellular biology, 1986
Maltose fermentation in Saccharomyces spp. requires the presence of a dominant MAL locus. The MAL6 locus has been cloned and shown to encode the structural genes for maltose permease (MAL61), maltase (MAL62), and a positively acting regulatory gene (MAL63). Induction of the MAL61 and MAL62 gene products requires the presence of maltose and the MAL63 gene. Mutations within the MAL63 gene produce nonfermenting strains unable to induce the two structural gene products. Reversion of these mal63 nonfermenters to maltose fermenters nearly always leads to the constitutive expression of maltase and maltose permease, and constitutivity is always linked to MAL6. We demonstrated that for one such revertant, strain C2, constitutivity did not require the MAL63 gene, since deletion disruption of this gene did not affect the constitutive expression of the structural genes. In addition, constitutivity was trans acting. Deletion disruption of the MAL6-linked structural genes for maltase and maltose ...
FEMS Microbiology Letters, 1991
The MALl locus of Saccharomyces cerevisiae comprises three genes necessary for maltose utilization. They include regulatory, maltose transport and maltase genes designated MAL1R, MAL1T and MALLS respectively. Using a MALl strain transformed with an episomal, multicopy plasmid carrying the MAL2 locus, five recessive and one dominant mutant unable to grow on maltose, but still retaining a functional MALl locus were isolated. All the mutants could use glycerol, ethanol, raffinose and sucrose as a sole carbon source; expression of the maltase and maltose permease genes was severely and coordinately reduced. Only the dominant mutant failed to accumulate the MAL1R mRNA.
FEMS Yeast Research, 2005
Hansenula polymorpha uses maltase to grow on maltose and sucrose. Inspection of genomic clones of H. polymorpha showed that the maltase gene HPMAL1 is clustered with genes corresponding to Saccharomyces cerevisiae maltose permeases and MAL activator genes orthologues. We sequenced the H. polymorpha maltose permease gene HPMAL2 of the cluster. The protein (582 amino acids) deduced from the HPMAL2 gene is predicted to have eleven transmembrane domains and shows 39-57% identity with yeast maltose permeases. The identity of the protein is highest with maltose permeases of Debaryomyces hansenii and Candida albicans. Expression of the HPMAL2 in a S. cerevisiae maltose permease-negative mutant CMY1050 proved functionality of the permease protein encoded by the gene. HPMAL1 and HPMAL2 genes are divergently positioned similarly to maltase and maltose permease genes in many yeasts. A two-reporter assay of the expression from the HPMAL1-HPMAL2 intergenic region showed that expression of both genes is coordinately regulated, repressed by glucose, induced by maltose, and that basal expression is higher in the direction of the permease gene.
Genetics, 1997
We report the sequence of several MALactivator genes, including inducible, constitutive, and noninducible alleles of MAL23, MAL43, MAL63, and ma164. Constitutive alleles of MAL23 and MAL43 vary considerably from inducible alleles in their C-terminal domain, with many of the alterations clustered and common to both alleles. The 27 alterations from residues 238-461 of Ma143-C protein are sufficient for constitutivity, but the minimal number of alterations needed for the constitutive phenotype could not be determined. The sequence of ma164, a nonfunctional homologue of MAL63, revealed that Ma164p is 85% identical to Ma163p. Two mutations that activate ma164 and cause constitutivity are nonsense mutations resulting in truncated proteins of 306 and 282 residues. We conclude that the C-terminal region of the MALactivator, from residues 283-470, contains a maltose-responsive negative regulatory domain, and that extensive mutation or deletion of the entire region causes loss of the negative regulatory function. Additionally, certain sequence elements in the region appear to be necessary for efficient induction of the full-length Ma163 activator protein. These studies highlight the role of ectopic recombination as an important mechanism of mutagenesis of the telomere-associated family of MAL loci. M ALTOSE fermentation in Saccharomyces requires the presence of one of five unlinked MAL loci: M A L I , MAL2, MAL3, MAL4 and MAL6 (reviewed in NEEDLEMAN 1991). Each locus encodes three gene products essential for maltose fermentation. Genes 1 and 2 encode maltose permease and maltase, respectively; gene 3 encodes the MAL transcriptional activator protein (HONG and MARMuR 1986; KIM and MICHELS 1988; CHENG and MICHELS 1989). At MAL6, the three genes are referred to as MAL61, MAL62, and MAL63 (see Figure 1). Transcription of the structural genes is induced by maltose and repressed by glucose (NEEDLE-MAN et al. 1984; CHARRON et al. 1986; LEVINE et al. 1992; HU et al. 1995). The MALactivator mediates both regulatory processes but is only one of several factors controlling glucose repression of maltose fermentation (Hu et al. 1995). Constitutive mutations, usually obtained by reversion of a nonfermenting strain to Mal', have been reported at all of the MAL loci, including MAL4 (WINGE and
Intracellular maltose is sufficient to induce MAL gene expression in Saccharomyces cerevisiae
Eukaryotic cell, 2002
The presence of maltose induces M4L gene expression in Saccharomyces cells, but little is known abouthow maltose is sensed. Strains with all maltose permease genes deleted are unable to induce MAL geneexpression. In this study, we examined the role of maltose permease in maltose sensing by substituting a heterologous transporter for the native maltose permease. PmSUC2 encodes a sucrose transporter from the dicot plant Plantago major that exhibits no significant sequence homology to maltose permease. When expressed in Saccharomyces cerevisiae, PmSUC2 is capable of transporting maltose, albeit at a reduced rate. We showed that introduction of PmSUC2 restores maltose-inducible MAL gene expression to a maltose permease-null mutant and that this induction requires the MAL activator. These data indicate that intracellular maltose is sufficient to induce MAL gene expression independently of the mechanism of maltose transport. By usingstrains expressing defective mal61 mutant alleles, we de...
Journal of Bacteriology
Saccharomyces yeasts ferment several aL-glucosides including maltose, maltotriose, turanose, a-methylglucoside, and melezitose. In the utilization of these sugars transport is the rate-limiting step. Several groups of investigators have described the characteristics of the maltose permease (D. E. Kroon and V. V. Koningsberger, Biochim. Biophys. Acta 204:590-609, 1970; R. Serrano, Eur. J. Biochem. 80:97-102, 1977). However, Saccharomyces contains multiple aL-glucoside transport systems, and these studies have never been performed on a genetically defined strain shown to have only a single permease gene. In this study we isolated maltose-negative mutants in a MAL6 strain and, using a high-resolution mapping technique, we showed that one class of these mutants, the group A mutants, mapped to the MAL61 gene (a member of the MAL6 gene complex). An insertion into the N-terminal-coding region of MAL61 resulted in the constitutive production of MAL61 mRNA and rendered the maltose permease similarly constitutive. Transformation by high-copynumber plasmids containing the MAL61 gene also led to an increase in the maltose permease. A deletiondisruption of MAL61 completely abolished maltose transport activity. Taken together, these results prove that this strain has only a single maltose permease and that this permease is the product of the MAL61 gene. This permease is able to transport maltose and turanose but cannot transport maltotriose, at-methylglucoside, or melezitose. The construction of strains with only a single permease will allow us to identify other maltoseinducible transport systems by simple genetic tests and should lead to the identification and characterization of the multiple genes and gene products involved in a-glucoside transport in Saccharomyces yeasts.
Genetics, 2000
Expression of the MAL genes required for maltose fermentation in Saccharomyces cerevisiae is induced by maltose and repressed by glucose. Maltose-inducible regulation requires maltose permease and the MAL-activator protein, a DNA-binding transcription factor encoded by MAL63 and its homologues at the other MAL loci. Previously, we showed that the Mig1 repressor mediates glucose repression of MAL gene expression. Glucose also blocks MAL-activator-mediated maltose induction through a Mig1p-independent mechanism that we refer to as glucose inhibition. Here we report the characterization of this process. Our results indicate that glucose inhibition is also Mig2p independent. Moreover, we show that neither overexpression of the MAL-activator nor elimination of inducer exclusion is sufficient to relieve glucose inhibition, suggesting that glucose acts to inhibit induction by affecting maltose sensing and/or signaling. The glucose inhibition pathway requires HXK2, REG1, and GSF1 and appear...