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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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Models for Met4 recruitment to MET (A) versus PDC6 (B) promoters. Met4 recruitment involves direct interactions with Cbf1 (through the bZIP domain) and Met31 or Met32 (through the ‘Int’ domain). Met28 associates with Met4 bZIP and participates in Met4 recruitment through stabilization of the Met4–Cbf1–DNA complex (see text for details and references). The question marks at the extremity of the arrows originating from Met4 bZIP indicate that, even though direct interactions with promoter DNA are likely [see ref. (16)], the precise points of contact remain to be established. At PDC6 promoter, Met31 and Met32 bind to two distinct sites. Met4 recruitment to this promoter requires interaction with Met32 specifically, and Met31 participates by assisting Met32 association with its binding site. The width of the arrows pointing toward Cbf1 and Met31/32 DNA binding sites translate the strength of the interaction, which differs between MET and PDC6 promoters.
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Figure 14: Models for Met4 recruitment to MET (A) versus PDC6 (B) promoters. Met4 recruitment involves direct interactions with Cbf1 (through the bZIP domain) and Met31 or Met32 (through the ‘Int’ domain). Met28 associates with Met4 bZIP and participates in Met4 recruitment through stabilization of the Met4–Cbf1–DNA complex (see text for details and references). The question marks at the extremity of the arrows originating from Met4 bZIP indicate that, even though direct interactions with promoter DNA are likely [see ref. (16)], the precise points of contact remain to be established. At PDC6 promoter, Met31 and Met32 bind to two distinct sites. Met4 recruitment to this promoter requires interaction with Met32 specifically, and Met31 participates by assisting Met32 association with its binding site. The width of the arrows pointing toward Cbf1 and Met31/32 DNA binding sites translate the strength of the interaction, which differs between MET and PDC6 promoters.

Mentions: It is striking that Met31 cannot support PDC6 transcription since it binds both CTGTGGC sites in vitro (Figure 4). The possibility that Met31 would not bind PDC6 in vivo seems unlikely if one considers that Met31 has a stimulating role on PDC6 transcription (Figure 1A). Moreover, the fact that inactivation of Met31 has a similar effect as deletion of the distal CTGTGGC box (compare Figures 1A and 3A) strongly suggests a functional relationship. A more likely explanation is that Met31 bound to CTGTGGC does not form an adequate platform to recruit Met4, whereas Met31 bound to AAACTGTGGC does, possibly because the presence of the A-stretch stabilizes the DNA–Met31–Met4 complex (see model Figure 14B). Therefore, the only role of Met31 at PDC6 would be to stimulate or facilitate Met32 binding to DNA. These results offer a novel example of interplay between two homologous zinc finger proteins. They also show for the first time that Met31 and Met32 have distinct binding specificities despite the high homology of their DNA-binding domains (40 identical residues plus three conservative changes in the 51-amino acid long domain containing the two C2H2 motifs).Figure 14.


Transcriptional plasticity through differential assembly of a multiprotein activation complex.

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

Models for Met4 recruitment to MET (A) versus PDC6 (B) promoters. Met4 recruitment involves direct interactions with Cbf1 (through the bZIP domain) and Met31 or Met32 (through the ‘Int’ domain). Met28 associates with Met4 bZIP and participates in Met4 recruitment through stabilization of the Met4–Cbf1–DNA complex (see text for details and references). The question marks at the extremity of the arrows originating from Met4 bZIP indicate that, even though direct interactions with promoter DNA are likely [see ref. (16)], the precise points of contact remain to be established. At PDC6 promoter, Met31 and Met32 bind to two distinct sites. Met4 recruitment to this promoter requires interaction with Met32 specifically, and Met31 participates by assisting Met32 association with its binding site. The width of the arrows pointing toward Cbf1 and Met31/32 DNA binding sites translate the strength of the interaction, which differs between MET and PDC6 promoters.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2926612&req=5

Figure 14: Models for Met4 recruitment to MET (A) versus PDC6 (B) promoters. Met4 recruitment involves direct interactions with Cbf1 (through the bZIP domain) and Met31 or Met32 (through the ‘Int’ domain). Met28 associates with Met4 bZIP and participates in Met4 recruitment through stabilization of the Met4–Cbf1–DNA complex (see text for details and references). The question marks at the extremity of the arrows originating from Met4 bZIP indicate that, even though direct interactions with promoter DNA are likely [see ref. (16)], the precise points of contact remain to be established. At PDC6 promoter, Met31 and Met32 bind to two distinct sites. Met4 recruitment to this promoter requires interaction with Met32 specifically, and Met31 participates by assisting Met32 association with its binding site. The width of the arrows pointing toward Cbf1 and Met31/32 DNA binding sites translate the strength of the interaction, which differs between MET and PDC6 promoters.
Mentions: It is striking that Met31 cannot support PDC6 transcription since it binds both CTGTGGC sites in vitro (Figure 4). The possibility that Met31 would not bind PDC6 in vivo seems unlikely if one considers that Met31 has a stimulating role on PDC6 transcription (Figure 1A). Moreover, the fact that inactivation of Met31 has a similar effect as deletion of the distal CTGTGGC box (compare Figures 1A and 3A) strongly suggests a functional relationship. A more likely explanation is that Met31 bound to CTGTGGC does not form an adequate platform to recruit Met4, whereas Met31 bound to AAACTGTGGC does, possibly because the presence of the A-stretch stabilizes the DNA–Met31–Met4 complex (see model Figure 14B). Therefore, the only role of Met31 at PDC6 would be to stimulate or facilitate Met32 binding to DNA. These results offer a novel example of interplay between two homologous zinc finger proteins. They also show for the first time that Met31 and Met32 have distinct binding specificities despite the high homology of their DNA-binding domains (40 identical residues plus three conservative changes in the 51-amino acid long domain containing the two C2H2 motifs).Figure 14.

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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