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Transcriptional plasticity through differential assembly of a multiprotein activation complex.

Cormier L, Barbey R, Kuras L - Nucleic Acids Res. (2010)

Bottom Line: Study of Cbf1 and Met31/32 association with PDC6 allowed us to find a new mechanism of recruitment of Met4, which allows PDC6 being differentially regulated compared to sulfur amino acid biosynthetic genes.Our findings provide a new example of mechanism allowing transcriptional plasticity within a regulatory network thanks to a definite toolbox comprising a unique master activator and several dedicated DNA-binding cofactors.We also show evidence suggesting that integration of PDC6 to the Met4 regulon may have occurred recently in the evolution of the Saccharomyces cerevisiae lineage.

View Article: PubMed Central - PubMed

Affiliation: CNRS, Centre de Génétique Moléculaire, Gif-sur-Yvette, France.

ABSTRACT
Cell adaptation to the environment often involves induction of complex gene expression programs under the control of specific transcriptional activators. For instance, in response to cadmium, budding yeast induces transcription of the sulfur amino acid biosynthetic genes through the basic-leucine zipper activator Met4, and also launches a program of substitution of abundant glycolytic enzymes by isozymes with a lower content in sulfur. We demonstrate here that transcriptional induction of PDC6, which encodes a pyruvate decarboxylase isoform with low sulfur content, is directly controlled by Met4 and its DNA-binding cofactors the basic-helix-loop-helix protein Cbf1 and the two homologous zinc finger proteins Met31 and Met32. Study of Cbf1 and Met31/32 association with PDC6 allowed us to find a new mechanism of recruitment of Met4, which allows PDC6 being differentially regulated compared to sulfur amino acid biosynthetic genes. Our findings provide a new example of mechanism allowing transcriptional plasticity within a regulatory network thanks to a definite toolbox comprising a unique master activator and several dedicated DNA-binding cofactors. We also show evidence suggesting that integration of PDC6 to the Met4 regulon may have occurred recently in the evolution of the Saccharomyces cerevisiae lineage.

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Dose–response relations between cadmium concentrations and transcription levels. WT cells grown to early log phase in YPD medium were exposed to various concentrations of Cd2+. Total RNA was extracted from samples taken at the time points indicated (no sample was taken at 30 min in the culture exposed to 500 µM Cd2+). RNA levels for PDC6, MET3 and MET17 were quantified by RT-real time PCR and normalized to 25S ribosomal RNA. Maximum values for each gene were set to 100 to facilitate comparisons. Error bars indicate average deviations from two independent experiments.
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Figure 9: Dose–response relations between cadmium concentrations and transcription levels. WT cells grown to early log phase in YPD medium were exposed to various concentrations of Cd2+. Total RNA was extracted from samples taken at the time points indicated (no sample was taken at 30 min in the culture exposed to 500 µM Cd2+). RNA levels for PDC6, MET3 and MET17 were quantified by RT-real time PCR and normalized to 25S ribosomal RNA. Maximum values for each gene were set to 100 to facilitate comparisons. Error bars indicate average deviations from two independent experiments.

Mentions: To better apprehend the logic of PDC6 regulation, we compared the dose response relations between the concentration of cadmium in the medium and the level of transcription of PDC6 and MET genes. WT cells were exposed to concentrations ranging from 10 to 500 µM and RNA levels of PDC6 and two representative MET genes were monitored for up to 3 h (Figure 9). For all three genes, we observed an overall positive correlation between the concentration of cadmium and the intensity of the transcriptional response. However, PDC6 transcription fell more abruptly than MET3 and MET17 transcription when cadmium concentration was diminished. For instance, the maximum of PDC6 transcripts at 50 µM was almost 10-fold lower than its maximum at 500 µM whereas, comparatively, the maxima of MET3 and MET17 transcripts were reduced by maximum 2-fold. Moreover, PDC6 transcription was undetectable at 10 µM cadmium whereas MET3 and MET17 were still transcribed at, respectively, 17 and 26% of their maximum levels. These results suggested that the threshold concentration of cadmium necessary to induce PDC6 was higher than that necessary to induce MET genes.Figure 9.


Transcriptional plasticity through differential assembly of a multiprotein activation complex.

Cormier L, Barbey R, Kuras L - Nucleic Acids Res. (2010)

Dose–response relations between cadmium concentrations and transcription levels. WT cells grown to early log phase in YPD medium were exposed to various concentrations of Cd2+. Total RNA was extracted from samples taken at the time points indicated (no sample was taken at 30 min in the culture exposed to 500 µM Cd2+). RNA levels for PDC6, MET3 and MET17 were quantified by RT-real time PCR and normalized to 25S ribosomal RNA. Maximum values for each gene were set to 100 to facilitate comparisons. Error bars indicate average deviations from two independent experiments.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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Figure 9: Dose–response relations between cadmium concentrations and transcription levels. WT cells grown to early log phase in YPD medium were exposed to various concentrations of Cd2+. Total RNA was extracted from samples taken at the time points indicated (no sample was taken at 30 min in the culture exposed to 500 µM Cd2+). RNA levels for PDC6, MET3 and MET17 were quantified by RT-real time PCR and normalized to 25S ribosomal RNA. Maximum values for each gene were set to 100 to facilitate comparisons. Error bars indicate average deviations from two independent experiments.
Mentions: To better apprehend the logic of PDC6 regulation, we compared the dose response relations between the concentration of cadmium in the medium and the level of transcription of PDC6 and MET genes. WT cells were exposed to concentrations ranging from 10 to 500 µM and RNA levels of PDC6 and two representative MET genes were monitored for up to 3 h (Figure 9). For all three genes, we observed an overall positive correlation between the concentration of cadmium and the intensity of the transcriptional response. However, PDC6 transcription fell more abruptly than MET3 and MET17 transcription when cadmium concentration was diminished. For instance, the maximum of PDC6 transcripts at 50 µM was almost 10-fold lower than its maximum at 500 µM whereas, comparatively, the maxima of MET3 and MET17 transcripts were reduced by maximum 2-fold. Moreover, PDC6 transcription was undetectable at 10 µM cadmium whereas MET3 and MET17 were still transcribed at, respectively, 17 and 26% of their maximum levels. These results suggested that the threshold concentration of cadmium necessary to induce PDC6 was higher than that necessary to induce MET genes.Figure 9.

Bottom Line: Study of Cbf1 and Met31/32 association with PDC6 allowed us to find a new mechanism of recruitment of Met4, which allows PDC6 being differentially regulated compared to sulfur amino acid biosynthetic genes.Our findings provide a new example of mechanism allowing transcriptional plasticity within a regulatory network thanks to a definite toolbox comprising a unique master activator and several dedicated DNA-binding cofactors.We also show evidence suggesting that integration of PDC6 to the Met4 regulon may have occurred recently in the evolution of the Saccharomyces cerevisiae lineage.

View Article: PubMed Central - PubMed

Affiliation: CNRS, Centre de Génétique Moléculaire, Gif-sur-Yvette, France.

ABSTRACT
Cell adaptation to the environment often involves induction of complex gene expression programs under the control of specific transcriptional activators. For instance, in response to cadmium, budding yeast induces transcription of the sulfur amino acid biosynthetic genes through the basic-leucine zipper activator Met4, and also launches a program of substitution of abundant glycolytic enzymes by isozymes with a lower content in sulfur. We demonstrate here that transcriptional induction of PDC6, which encodes a pyruvate decarboxylase isoform with low sulfur content, is directly controlled by Met4 and its DNA-binding cofactors the basic-helix-loop-helix protein Cbf1 and the two homologous zinc finger proteins Met31 and Met32. Study of Cbf1 and Met31/32 association with PDC6 allowed us to find a new mechanism of recruitment of Met4, which allows PDC6 being differentially regulated compared to sulfur amino acid biosynthetic genes. Our findings provide a new example of mechanism allowing transcriptional plasticity within a regulatory network thanks to a definite toolbox comprising a unique master activator and several dedicated DNA-binding cofactors. We also show evidence suggesting that integration of PDC6 to the Met4 regulon may have occurred recently in the evolution of the Saccharomyces cerevisiae lineage.

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