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Partially phosphorylated Pho4 activates transcription of a subset of phosphate-responsive genes.

Springer M, Wykoff DD, Miller N, O'Shea EK - PLoS Biol. (2003)

Bottom Line: This Pho4 phosphoform binds differentially to phosphate-responsive promoters and helps to trigger differential gene expression.Our results demonstrate that three transcriptional outputs can be generated by a pathway whose regulation is controlled by one kinase, Pho80-Pho85, and one transcription factor, Pho4.Differential phosphorylation of Pho4 by Pho80-Pho85 produces phosphorylated forms of Pho4 that differ in their ability to activate transcription, contributing to multiple outputs.

View Article: PubMed Central - PubMed

Affiliation: Howard Hughes Medical Institute, Department of Biochemistry and Biophysics, University of California, San Francisco, USA.

ABSTRACT
A cell's ability to generate different responses to different levels of stimulus is an important component of an adaptive environmental response. Transcriptional responses are frequently controlled by transcription factors regulated by phosphorylation. We demonstrate that differential phosphorylation of the budding yeast transcription factor Pho4 contributes to differential gene expression. When yeast cells are grown in high-phosphate growth medium, Pho4 is phosphorylated on four critical residues by the cyclin-CDK complex Pho80-Pho85 and is inactivated. When yeast cells are starved for phosphate, Pho4 is dephosphorylated and fully active. In intermediate-phosphate conditions, a form of Pho4 preferentially phosphorylated on one of the four sites accumulates and activates transcription of a subset of phosphate-responsive genes. This Pho4 phosphoform binds differentially to phosphate-responsive promoters and helps to trigger differential gene expression. Our results demonstrate that three transcriptional outputs can be generated by a pathway whose regulation is controlled by one kinase, Pho80-Pho85, and one transcription factor, Pho4. Differential phosphorylation of Pho4 by Pho80-Pho85 produces phosphorylated forms of Pho4 that differ in their ability to activate transcription, contributing to multiple outputs.

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A Strain Expressing Pho4 That Cannot Be Phosphorylated on Site 6 Does Not Induce PHO5 in Intermediate-Phosphate MediumA strain expressing Pho4WT1234PA6 grown for 2 h in no-, intermediate-, and high-phosphate medium was analyzed by Northern blot analysis (A) and chromatin immunoprecipitation (B). The fold enrichment of PHO5 over ACT1 was 1.71, 2.42, 10.49, 0.99, 1.26, and 2.84 in lanes 1–6, respectively (PHO4WT1234WT6 high, PHO4WT1234WT6 int, PHO4 WT1234WT6 no, wt high, wt int, wt no). The fold enrichment of PHO84 over ACT1 was 24.64, 27.44, 43.74, 1.75, 4.27, and 6.28 in lanes 1–6, respectively.
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pbio.0000028-g004: A Strain Expressing Pho4 That Cannot Be Phosphorylated on Site 6 Does Not Induce PHO5 in Intermediate-Phosphate MediumA strain expressing Pho4WT1234PA6 grown for 2 h in no-, intermediate-, and high-phosphate medium was analyzed by Northern blot analysis (A) and chromatin immunoprecipitation (B). The fold enrichment of PHO5 over ACT1 was 1.71, 2.42, 10.49, 0.99, 1.26, and 2.84 in lanes 1–6, respectively (PHO4WT1234WT6 high, PHO4WT1234WT6 int, PHO4 WT1234WT6 no, wt high, wt int, wt no). The fold enrichment of PHO84 over ACT1 was 24.64, 27.44, 43.74, 1.75, 4.27, and 6.28 in lanes 1–6, respectively.

Mentions: Although site 6 phosphorylation is not necessary to inhibit PHO5 expression, it is necessary to keep cells from inducing transcription of PHO84 in high-phosphate medium. A strain expressing Pho4WT1234PA6 grown in high-phosphate medium had levels of PHO5 and PHO84 expression that were similar to those of a wild-type strain grown in intermediate-phosphate medium (see Figure 4A). Site 6 phosphorylation was necessary to inhibit binding of Pho4 to the PHO84 promoter in high-phosphate medium, but was not required to inhibit binding of Pho4 to the PHO5 promoter in intermediate-phosphate medium (see Figure 4B).


Partially phosphorylated Pho4 activates transcription of a subset of phosphate-responsive genes.

Springer M, Wykoff DD, Miller N, O'Shea EK - PLoS Biol. (2003)

A Strain Expressing Pho4 That Cannot Be Phosphorylated on Site 6 Does Not Induce PHO5 in Intermediate-Phosphate MediumA strain expressing Pho4WT1234PA6 grown for 2 h in no-, intermediate-, and high-phosphate medium was analyzed by Northern blot analysis (A) and chromatin immunoprecipitation (B). The fold enrichment of PHO5 over ACT1 was 1.71, 2.42, 10.49, 0.99, 1.26, and 2.84 in lanes 1–6, respectively (PHO4WT1234WT6 high, PHO4WT1234WT6 int, PHO4 WT1234WT6 no, wt high, wt int, wt no). The fold enrichment of PHO84 over ACT1 was 24.64, 27.44, 43.74, 1.75, 4.27, and 6.28 in lanes 1–6, respectively.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC261874&req=5

pbio.0000028-g004: A Strain Expressing Pho4 That Cannot Be Phosphorylated on Site 6 Does Not Induce PHO5 in Intermediate-Phosphate MediumA strain expressing Pho4WT1234PA6 grown for 2 h in no-, intermediate-, and high-phosphate medium was analyzed by Northern blot analysis (A) and chromatin immunoprecipitation (B). The fold enrichment of PHO5 over ACT1 was 1.71, 2.42, 10.49, 0.99, 1.26, and 2.84 in lanes 1–6, respectively (PHO4WT1234WT6 high, PHO4WT1234WT6 int, PHO4 WT1234WT6 no, wt high, wt int, wt no). The fold enrichment of PHO84 over ACT1 was 24.64, 27.44, 43.74, 1.75, 4.27, and 6.28 in lanes 1–6, respectively.
Mentions: Although site 6 phosphorylation is not necessary to inhibit PHO5 expression, it is necessary to keep cells from inducing transcription of PHO84 in high-phosphate medium. A strain expressing Pho4WT1234PA6 grown in high-phosphate medium had levels of PHO5 and PHO84 expression that were similar to those of a wild-type strain grown in intermediate-phosphate medium (see Figure 4A). Site 6 phosphorylation was necessary to inhibit binding of Pho4 to the PHO84 promoter in high-phosphate medium, but was not required to inhibit binding of Pho4 to the PHO5 promoter in intermediate-phosphate medium (see Figure 4B).

Bottom Line: This Pho4 phosphoform binds differentially to phosphate-responsive promoters and helps to trigger differential gene expression.Our results demonstrate that three transcriptional outputs can be generated by a pathway whose regulation is controlled by one kinase, Pho80-Pho85, and one transcription factor, Pho4.Differential phosphorylation of Pho4 by Pho80-Pho85 produces phosphorylated forms of Pho4 that differ in their ability to activate transcription, contributing to multiple outputs.

View Article: PubMed Central - PubMed

Affiliation: Howard Hughes Medical Institute, Department of Biochemistry and Biophysics, University of California, San Francisco, USA.

ABSTRACT
A cell's ability to generate different responses to different levels of stimulus is an important component of an adaptive environmental response. Transcriptional responses are frequently controlled by transcription factors regulated by phosphorylation. We demonstrate that differential phosphorylation of the budding yeast transcription factor Pho4 contributes to differential gene expression. When yeast cells are grown in high-phosphate growth medium, Pho4 is phosphorylated on four critical residues by the cyclin-CDK complex Pho80-Pho85 and is inactivated. When yeast cells are starved for phosphate, Pho4 is dephosphorylated and fully active. In intermediate-phosphate conditions, a form of Pho4 preferentially phosphorylated on one of the four sites accumulates and activates transcription of a subset of phosphate-responsive genes. This Pho4 phosphoform binds differentially to phosphate-responsive promoters and helps to trigger differential gene expression. Our results demonstrate that three transcriptional outputs can be generated by a pathway whose regulation is controlled by one kinase, Pho80-Pho85, and one transcription factor, Pho4. Differential phosphorylation of Pho4 by Pho80-Pho85 produces phosphorylated forms of Pho4 that differ in their ability to activate transcription, contributing to multiple outputs.

Show MeSH
Related in: MedlinePlus