Dataset Information

Gal80 proteins of Kluyveromyces lactis and Saccharomyces cerevisiae are highly conserved but contribute differently to glucose repression of the galactose regulon.

ABSTRACT: We cloned the GAL80 gene encoding the negative regulator of the transcriptional activator Gal4 (Lac9) from the yeast Kluyveromyces lactis. The deduced amino acid sequence of K. lactis GAL80 revealed a strong structural conservation between K. lactis Gal80 and the homologous Saccharomyces cerevisiae protein, with an overall identity of 60% and two conserved blocks with over 80% identical residues. K. lactis gal80 disruption mutants show constitutive expression of the lactose/galactose metabolic genes, confirming that K. lactis Gal80 functions in essentially in the same way as does S. cerevisiae Gal80, blocking activation by the transcriptional activator Lac9 (K. lactis Gal4) in the absence of an inducing sugar. However, in contrast to S. cerevisiae, in which Gal4-dependent activation is strongly inhibited by glucose even in a gal80 mutant, glucose repressibility is almost completely lost in gal80 mutants of K. lactis. Indirect evidence suggests that this difference in phenotype is due to a higher activator concentration in K. lactis which is able to overcome glucose repression. Expression of the K. lactis GAL80 gene is controlled by Lac9. Two high-affinity binding sites in the GAL80 promoter mediate a 70-fold induction by galactose and hence negative autoregulation by Gal80. Gal80 in turn not only controls Lac9 activity but also has a moderate influence on its rate of synthesis. Thus, a feedback control mechanism exists between the positive and negative regulators. By mutating the Lac9 binding sites of the GAL80 promoter, we could show that induction of GAL80 is required to prevent activation of the lactose/galactose regulon in glycerol or glucose plus galactose, whereas the noninduced level of Gal80 is sufficient to completely block Lac9 function in glucose.

SUBMITTER: Zenke FT

PROVIDER: S-EPMC364828 | biostudies-other | 1993 Dec

REPOSITORIES: biostudies-other

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Gal80 proteins of Kluyveromyces lactis and Saccharomyces cerevisiae are highly conserved but contribute differently to glucose repression of the galactose regulon.

Zenke F T FT Zachariae W W Lunkes A A Breunig K D KD

Molecular and cellular biology 19931201 12

We cloned the GAL80 gene encoding the negative regulator of the transcriptional activator Gal4 (Lac9) from the yeast Kluyveromyces lactis. The deduced amino acid sequence of K. lactis GAL80 revealed a strong structural conservation between K. lactis Gal80 and the homologous Saccharomyces cerevisiae protein, with an overall identity of 60% and two conserved blocks with over 80% identical residues. K. lactis gal80 disruption mutants show constitutive expression of the lactose/galactose metabolic g ...[more]

PMID: 8246973

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Project description:The transcription factor KlPdr1p, belonging to the Zn2Cys6 family, is a central regulator of efflux pump expression in Kluyveromyces lactis. To better understand how KlPDR1-mediated drug resistance is achieved in K. lactis, we used DNA microarrays to identify genes whose expression was affected by deletion or overexpression of the KlPDR1 gene. All microarray experiments were performed using the 30K Kluyveromyces lactis NRRL Y-1140 microarray (MYcroarray, 5692 Plymouth Road, Ann Arbor, MI 48105, USA). Exponentially growing (1 x 107 cells ml-1) K. lactis PM6-7A cells (wild-type, PM6-7A/pdr1∆ and the wild-type transformed with multicopy plasmid carrying the gain-of-function allele of KlPDR1* gene) (Balazfyova et al. 2013), were collected and total RNA was isolated using RNeasy midi kit (Qiagen GmbH, Germany). 1 mg of total RNA was linearly amplified and labelled using Amino allyl MessageAmpII aRNA Amplification kit (Ambion, USA) with two different fluorescent dyes; AlexaFluor647 and AlexaFluor555 (Life Technologies, Germany). 4 µg of labelled RNA was hybridized (18 h at 45°C) in 6x SSPE with addition of formamide (10%), tween-20 (0,01%) and microarray-specofoc control oligos (1%, MYcroarray, USA). After washing, microarray images and two-color GPR output files were obtained using the microarray scanner InnoScan 900 and Mapix software version 7.3.1 (Inopsys, France). The two-color GPR files were processed using the R version 3.0.2 (R Core Team (2014). R: A language and enviroment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. URL http://www.R-project.org) and functions available in the limma package (Smyth 2005). Briefly, the two-color GPR files were omported using the read.maimages() function, background-substracted using the “minimum“ method and within-array-normalized using the “loess“ method. The between-array normalisation was achieved using the “Aquantile“ method. For further analysis, only genes with log2FC ˃2 were selected and confirmed using qPCR.

Project description:BackgroundGene duplication is a key evolutionary mechanism providing material for the generation of genes with new or modified functions. The fate of duplicated gene copies has been amply discussed and several models have been put forward to account for duplicate conservation. The specialization model considers that duplication of a bifunctional ancestral gene could result in the preservation of both copies through subfunctionalization, resulting in the distribution of the two ancestral functions between the gene duplicates. Here we investigate whether the presumed bifunctional character displayed by the single branched chain amino acid aminotransferase present in K. lactis has been distributed in the two paralogous genes present in S. cerevisiae, and whether this conservation has impacted S. cerevisiae metabolism.Principal findingsOur results show that the KlBat1 orthologous BCAT is a bifunctional enzyme, which participates in the biosynthesis and catabolism of branched chain aminoacids (BCAAs). This dual role has been distributed in S. cerevisiae Bat1 and Bat2 paralogous proteins, supporting the specialization model posed to explain the evolution of gene duplications. BAT1 is highly expressed under biosynthetic conditions, while BAT2 expression is highest under catabolic conditions. Bat1 and Bat2 differential relocalization has favored their physiological function, since biosynthetic precursors are generated in the mitochondria (Bat1), while catabolic substrates are accumulated in the cytosol (Bat2). Under respiratory conditions, in the presence of ammonium and BCAAs the bat1? bat2? double mutant shows impaired growth, indicating that Bat1 and Bat2 could play redundant roles. In K. lactis wild type growth is independent of BCAA degradation, since a Klbat1? mutant grows under this condition.ConclusionsOur study shows that BAT1 and BAT2 differential expression and subcellular relocalization has resulted in the distribution of the biosynthetic and catabolic roles of the ancestral BCAT in two isozymes improving BCAAs metabolism and constituting an adaptation to facultative metabolism.

Dataset Information

Gal80 proteins of Kluyveromyces lactis and Saccharomyces cerevisiae are highly conserved but contribute differently to glucose repression of the galactose regulon.

Publications

Gal80 proteins of Kluyveromyces lactis and Saccharomyces cerevisiae are highly conserved but contribute differently to glucose repression of the galactose regulon.

Similar Datasets

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