Molecular basis of nutrient-controlled gene expression in Saccharomyces cerevisiae

Reece, Richard J.

doi:10.1007/pl00000756

Cited by 29 publications

(23 citation statements)

References 72 publications

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“…ENETIC regulation of transcriptional initiation occurs through environmentally responsive molecular switching systems that facilitate cellular differentiation (Reece 2000;Forsberg and Ljungdahl 2001). One such system in eukaryotes is the Saccharomyces cerevisiae GAL gene switch that regulates galactose-responsive transcription through the interplay of the Gal4, Gal80, and Gal3 proteins (Carlson 1987;Johnston 1987;Lohr et al 1995;Traven et al 2006).…”

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confidence: 99%

Rapid GAL Gene Switch of Saccharomyces cerevisiae Depends on Nuclear Gal3, Not Nucleocytoplasmic Trafficking of Gal3 and Gal80

Egriboz¹,

Jiang

Hopper

2011

Genetics

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The yeast transcriptional activator Gal4 localizes to UAS GAL sites even in the absence of galactose but cannot activate transcription due to an association with the Gal80 protein. By 4 min after galactose addition, Gal4-activated gene transcription ensues. It is well established that this rapid induction arises through a galactose-triggered association between the Gal80 and Gal3 proteins that decreases the association of Gal80 and Gal4. How this happens mechanistically remains unclear. Strikingly different hypotheses prevail concerning the possible roles of nucleocytoplasmic distribution and trafficking of Gal3 and Gal80 and where in the cell the initial Gal3-Gal80 association occurs. Here we tested two conflicting hypotheses by evaluating the subcellular distribution and dynamics of Gal3 and Gal80 with reference to induction kinetics. We determined that the rates of nucleocytoplasmic trafficking for both Gal80 and Gal3 are slow relative to the rate of induction. We find that depletion of the nuclear pool of Gal3 slows the induction kinetics. Thus, nuclear Gal3 is critical for rapid induction. Fluorescence-recovery-after-photobleaching experiments provided data suggesting that the Gal80-Gal4 complex exhibits kinetic stability in the absence of galactose. Finally, we detect Gal3 at the UAS GAL only if Gal80 is covalently linked to the DNA-binding domain. Taken altogether, these new findings lead us to propose that a transient interaction of Gal3 with Gal4-associated Gal80 could explain the rapid response of this system. This notion could also explain earlier observations.

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Rapid GAL Gene Switch of Saccharomyces cerevisiae Depends on Nuclear Gal3, Not Nucleocytoplasmic Trafficking of Gal3 and Gal80

Egriboz¹,

Jiang

Hopper

2011

Genetics

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“…The Saccharomyces cerevisiae GAL genes encode the enzymes of the Leloir pathway that are required to catalyze the conversion of galactose into a more metabolically useful version, glucose-6-phosphate (12,14,16,(23)(24)(25). When yeast cells are grown in the absence of galactose, the GAL genes are largely transcriptionally inert.…”

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Localization and Interaction of the Proteins Constituting the GAL Genetic Switch in Saccharomyces cerevisiae

2008

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In Saccharomyces cerevisiae, the GAL genes encode the enzymes required for galactose metabolism. Regulation of these genes has served as the paradigm for eukaryotic transcriptional control over the last 50 years. The switch between inert and active gene expression is dependent upon three proteins-the transcriptional activator Gal4p, the inhibitor Gal80p, and the ligand sensor Gal3p. Here, we present a detailed spatial analysis of the three GAL regulatory proteins produced from their native genomic loci. Using a novel application of photobleaching, we demonstrate, for the first time, that the Gal3p ligand sensor enters the nucleus of yeast cells in the presence of galactose. Additionally, using Förster resonance energy transfer, we show that the interaction between Gal3p and Gal80p occurs throughout the yeast cell. Taken together, these data challenge existing models for the cellular localization of the regulatory proteins during the induction of GAL gene expression by galactose and suggest a mechanism for the induction of the GAL genes in which galactose-bound Gal3p moves from the cytoplasm to the nucleus to interact with the transcriptional inhibitor Gal80p.

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“…In the yeast, Saccharomyces cerevisiae, the genes encoding these four enzymatic functions (collectively termed the GAL genes) are coordinately regulated at the level of transcription (2). The GAL genes are essentially inert in yeast cells grown in the absence of galactose, but the genes are rapidly expressed, and to a high level, when the cells are switched to a medium containing galactose as the sole carbon source (3).…”

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Molecular Structure of Saccharomyces cerevisiae Gal1p, a Bifunctional Galactokinase and Transcriptional Inducer

Thoden

Sellick

Timson

et al. 2005

Journal of Biological Chemistry

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Gal1p of Saccharomyces cerevisiae is capable of performing two independent cellular functions. First, it is a key enzyme in the Leloir pathway for galactose metabolism where it catalyzes the conversion of ␣-D-galactose to galactose 1-phosphate. Second, it has the capacity to induce the transcription of the yeast GAL genes in response to the organism being challenged with galactose as the sole source of carbon. This latter function is normally performed by a highly related protein, Gal3p, but in its absence Gal1p can induce transcription, albeit inefficiently, both in vivo and in vitro. Here we report the x-ray structure of Gal1p in complex with ␣-D-galactose and Mg-adenosine 5-(␤,␥-imido)triphosphate (AMPPNP) determined to 2.4 Å resolution. Overall, the enzyme displays a marked bilobal appearance with the active site being wedged between distinct N-and C-terminal domains. Despite being considerably larger than other galactokinases, Gal1p shares a similar molecular architecture with these enzymes as well as with other members of the GHMP superfamily. The extraordinary levels of similarity between Gal1p and Gal3p (ϳ70% amino acid identity and ϳ90% similarity) have allowed a model for Gal3p to be constructed. By identifying the locations of mutations of Gal3p that result in altered transcriptional properties, we suggest potential models for Gal3p function and mechanisms for its interaction with the transcriptional inhibitor Gal80p. The GAL genetic switch has long been regarded as a paradigm for the control of gene expression in eukaryotes. Understanding the manner in which two of the proteins that function in transcriptional regulation interact with one another is an important step in determining the overall molecular mechanism of this switch.There are four enzymes in the Leloir pathway that are responsible for the conversion of ␤-D-galactose to the more metabolically useful glucose 1-phosphate (1). In the first step of this pathway, ␤-D-galactose is epimerized to ␣-D-galactose by galactose mutarotase. The following step involves the ATP-dependent addition of a phosphate group to the galactose C-1 hydroxyl by galactokinase to yield galactose 1-phosphate. Subsequently, a UMP moiety, derived from UDP-glucose, is transferred to galactose 1-phosphate to generate glucose 1-phosphate and UDPgalactose. This reaction is catalyzed by galactose-1-phosphate uridylyltransferase. To complete the pathway, UDP-galactose is converted to UDP-glucose by UDP-galactose 4-epimerase.

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Molecular basis of nutrient-controlled gene expression in Saccharomyces cerevisiae

Cited by 29 publications

References 72 publications

Rapid GAL Gene Switch of Saccharomyces cerevisiae Depends on Nuclear Gal3, Not Nucleocytoplasmic Trafficking of Gal3 and Gal80

Rapid GAL Gene Switch of Saccharomyces cerevisiae Depends on Nuclear Gal3, Not Nucleocytoplasmic Trafficking of Gal3 and Gal80

Localization and Interaction of the Proteins Constituting the GAL Genetic Switch in Saccharomyces cerevisiae

Molecular Structure of Saccharomyces cerevisiae Gal1p, a Bifunctional Galactokinase and Transcriptional Inducer

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