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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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Whole-Genome Expression DNA Microarrays of PHO4SA1234WT6 and PHO4SA1234PA6 Strains(A) Schematic showing phosphorylation sites (O'Neill et al. 1996), the transcriptional activation domain (McAndrew et al. 1998), the nuclear localization sequence (Kaffman et al. 1998b), the Pho2-binding domain (Hirst et al. 1994), and the DNA-binding domain of Pho4 (Ogawa and Oshima 1990). Pho4 is phosphorylated on five sites (referred to as sites 1, 2, 3, 4, and 6) by Pho80–Pho85 (O'Neill et al. 1996). Site 1 is phosphorylated inefficiently in vivo and in vitro, and no functional consequence has been attributed to its phosphorylation (O'Neill et al. 1996; Komeili and O'Shea 1999).(B) Color scheme denoting the fold induction/repression for all of the microarray experiments.(C) Expression of phosphate-responsive genes in strains containing Pho4SA1234WT6 and Pho4SA1234PA6 grown in high-phosphate medium. Cy5-labeled samples are colored red, and Cy3-labeled samples are colored green. The percent of induction of each gene in the Pho4SA1234WT6 strain compared to its maximal induction in the Pho4SA1234PA6 strain is presented on the right. Several phosphate-responsive genes (PHO5, PHO8, PHO11, and PHO12) share large regions of homology. Cross-hybridization leads to similar response profiles even though the genes probably respond differently.
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pbio.0000028-g001: Whole-Genome Expression DNA Microarrays of PHO4SA1234WT6 and PHO4SA1234PA6 Strains(A) Schematic showing phosphorylation sites (O'Neill et al. 1996), the transcriptional activation domain (McAndrew et al. 1998), the nuclear localization sequence (Kaffman et al. 1998b), the Pho2-binding domain (Hirst et al. 1994), and the DNA-binding domain of Pho4 (Ogawa and Oshima 1990). Pho4 is phosphorylated on five sites (referred to as sites 1, 2, 3, 4, and 6) by Pho80–Pho85 (O'Neill et al. 1996). Site 1 is phosphorylated inefficiently in vivo and in vitro, and no functional consequence has been attributed to its phosphorylation (O'Neill et al. 1996; Komeili and O'Shea 1999).(B) Color scheme denoting the fold induction/repression for all of the microarray experiments.(C) Expression of phosphate-responsive genes in strains containing Pho4SA1234WT6 and Pho4SA1234PA6 grown in high-phosphate medium. Cy5-labeled samples are colored red, and Cy3-labeled samples are colored green. The percent of induction of each gene in the Pho4SA1234WT6 strain compared to its maximal induction in the Pho4SA1234PA6 strain is presented on the right. Several phosphate-responsive genes (PHO5, PHO8, PHO11, and PHO12) share large regions of homology. Cross-hybridization leads to similar response profiles even though the genes probably respond differently.

Mentions: When starved for inorganic phosphate, Saccharomyces cerevisiae induces a program of gene expression that includes a phosphate permease, Pho84 (NP_013583); a secreted acid phosphatase, Pho5 (NP_009651); and proteins involved in phosphate storage (Oshima 1982; Ogawa et al. 2000). Induction of the phosphate-responsive gene expression program is controlled by the transcription factor Pho4 (NP_116692) (Oshima 1997). Activity and localization of Pho4 are regulated in response to phosphate availability through phosphorylation by the nuclear cyclin–CDK (cyclin-dependent kinase) complex, Pho80–Pho85 (NP_014642 and NP_015294) (O'Neill et al. 1996; Komeili and O'Shea 1999). Pho4 is unphosphorylated, nuclear-localized, and active when yeast cells are starved for phosphate, but is phosphorylated, cytoplasmic, and inactive when cells are grown in phosphate-rich medium (Kaffman et al. 1994; O'Neill et al. 1996). Pho4 is phosphorylated by Pho80–Pho85 on four functionally important serine residues (O'Neill et al. 1996) (Figure 1A). Together, phosphorylation of sites 2 and 3 results in export of Pho4 from the nucleus by promoting its interaction with the export receptor Msn5 (NP_010622) (Kaffman et al. 1998a). Phosphorylation of site 4 inhibits nuclear import of Pho4 by impairing its binding to the import receptor Pse1 (NP_014039) (Kaffman et al. 1998b). Phosphorylation of Pho4 also regulates its transcriptional activity within the nucleus; phosphorylation of site 6 inhibits the binding of Pho4 to Pho2 (NP_010177), a transcription factor essential for the induction of many phosphate-responsive genes (Komeili and O'Shea 1999).


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

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

Whole-Genome Expression DNA Microarrays of PHO4SA1234WT6 and PHO4SA1234PA6 Strains(A) Schematic showing phosphorylation sites (O'Neill et al. 1996), the transcriptional activation domain (McAndrew et al. 1998), the nuclear localization sequence (Kaffman et al. 1998b), the Pho2-binding domain (Hirst et al. 1994), and the DNA-binding domain of Pho4 (Ogawa and Oshima 1990). Pho4 is phosphorylated on five sites (referred to as sites 1, 2, 3, 4, and 6) by Pho80–Pho85 (O'Neill et al. 1996). Site 1 is phosphorylated inefficiently in vivo and in vitro, and no functional consequence has been attributed to its phosphorylation (O'Neill et al. 1996; Komeili and O'Shea 1999).(B) Color scheme denoting the fold induction/repression for all of the microarray experiments.(C) Expression of phosphate-responsive genes in strains containing Pho4SA1234WT6 and Pho4SA1234PA6 grown in high-phosphate medium. Cy5-labeled samples are colored red, and Cy3-labeled samples are colored green. The percent of induction of each gene in the Pho4SA1234WT6 strain compared to its maximal induction in the Pho4SA1234PA6 strain is presented on the right. Several phosphate-responsive genes (PHO5, PHO8, PHO11, and PHO12) share large regions of homology. Cross-hybridization leads to similar response profiles even though the genes probably respond differently.
© Copyright Policy
Related In: Results  -  Collection

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

pbio.0000028-g001: Whole-Genome Expression DNA Microarrays of PHO4SA1234WT6 and PHO4SA1234PA6 Strains(A) Schematic showing phosphorylation sites (O'Neill et al. 1996), the transcriptional activation domain (McAndrew et al. 1998), the nuclear localization sequence (Kaffman et al. 1998b), the Pho2-binding domain (Hirst et al. 1994), and the DNA-binding domain of Pho4 (Ogawa and Oshima 1990). Pho4 is phosphorylated on five sites (referred to as sites 1, 2, 3, 4, and 6) by Pho80–Pho85 (O'Neill et al. 1996). Site 1 is phosphorylated inefficiently in vivo and in vitro, and no functional consequence has been attributed to its phosphorylation (O'Neill et al. 1996; Komeili and O'Shea 1999).(B) Color scheme denoting the fold induction/repression for all of the microarray experiments.(C) Expression of phosphate-responsive genes in strains containing Pho4SA1234WT6 and Pho4SA1234PA6 grown in high-phosphate medium. Cy5-labeled samples are colored red, and Cy3-labeled samples are colored green. The percent of induction of each gene in the Pho4SA1234WT6 strain compared to its maximal induction in the Pho4SA1234PA6 strain is presented on the right. Several phosphate-responsive genes (PHO5, PHO8, PHO11, and PHO12) share large regions of homology. Cross-hybridization leads to similar response profiles even though the genes probably respond differently.
Mentions: When starved for inorganic phosphate, Saccharomyces cerevisiae induces a program of gene expression that includes a phosphate permease, Pho84 (NP_013583); a secreted acid phosphatase, Pho5 (NP_009651); and proteins involved in phosphate storage (Oshima 1982; Ogawa et al. 2000). Induction of the phosphate-responsive gene expression program is controlled by the transcription factor Pho4 (NP_116692) (Oshima 1997). Activity and localization of Pho4 are regulated in response to phosphate availability through phosphorylation by the nuclear cyclin–CDK (cyclin-dependent kinase) complex, Pho80–Pho85 (NP_014642 and NP_015294) (O'Neill et al. 1996; Komeili and O'Shea 1999). Pho4 is unphosphorylated, nuclear-localized, and active when yeast cells are starved for phosphate, but is phosphorylated, cytoplasmic, and inactive when cells are grown in phosphate-rich medium (Kaffman et al. 1994; O'Neill et al. 1996). Pho4 is phosphorylated by Pho80–Pho85 on four functionally important serine residues (O'Neill et al. 1996) (Figure 1A). Together, phosphorylation of sites 2 and 3 results in export of Pho4 from the nucleus by promoting its interaction with the export receptor Msn5 (NP_010622) (Kaffman et al. 1998a). Phosphorylation of site 4 inhibits nuclear import of Pho4 by impairing its binding to the import receptor Pse1 (NP_014039) (Kaffman et al. 1998b). Phosphorylation of Pho4 also regulates its transcriptional activity within the nucleus; phosphorylation of site 6 inhibits the binding of Pho4 to Pho2 (NP_010177), a transcription factor essential for the induction of many phosphate-responsive genes (Komeili and O'Shea 1999).

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