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Published on: November 8, 2006
CK2-dependent phosphorylation positively regulates stress-induced activation of Msn2 in Saccharomyces cerevisiae
1Interdisciplinary Program for Bioengineering, Institute of Chemical Processes, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea.
Abstract:
CK2 is a highly conserved Ser/Thr protein kinase involved in a large number of cellular processes. Here, we demonstrate that CK2-dependent phosphorylation positively regulates Msn2/4, the general stress response transcriptional activators in Saccharomyces cerevisiae, in response to various types of environmental stress conditions. CK2 overexpression elicits hyperactivation of Msn2/4, whereas deletion of one of the CK2 catalytic subunits, especially CKA2, leads to reduced transcriptional activity of Msn2/4 in response to glucose starvation, H2O2, and lactic acid. The CKA2 deletion mutant also shows increased stress sensitivity. CK2 phosphorylates Ser194 and Ser638 in Msn2 and replacement of Ser638 with alanine leads to reduced Msn2 activity upon stress and reduced tolerance to H2O2 and lactic acid. CKA2 deletion mutant shows shorter nuclear retention time of Msn2 upon lactic acid stress, suggesting that CK2 might regulate nuclear localization of Msn2. However, Msn2S194A, S638A mutant shows normal nuclear import and export patterns upon stress, suggesting that CK2 might positively regulate the general stress response not only by direct phosphorylation of Msn2/4, but also by regulating cellular translocation machinery.
Insights
Protein kinase CK2 positively regulates the general stress response in yeast by phosphorylating Msn2/4 transcriptional activators. CK2 activity is crucial for yeast survival under stress conditions.
Area of Science:
- Molecular Biology
- Cellular Biology
- Biochemistry
Background:
- Casein kinase 2 (CK2) is a vital protein kinase regulating numerous cellular functions.
- Msn2 and Msn4 (Msn2/4) are key transcriptional activators of the general stress response in Saccharomyces cerevisiae.
Purpose of the Study:
- To investigate the role of CK2 in regulating Msn2/4 activity and the general stress response in yeast.
- To identify specific phosphorylation sites on Msn2 regulated by CK2.
Main Methods:
- Yeast genetics (gene deletion and overexpression).
- Analysis of transcriptional activity of Msn2/4 under various stress conditions.
- Site-directed mutagenesis of Msn2 phosphorylation sites.
- Microscopy to assess Msn2 nuclear localization.
Main Results:
- CK2 positively regulates Msn2/4 activity in response to environmental stress.
- Deletion of the CKA2 gene (encoding a CK2 catalytic subunit) reduces Msn2/4 transcriptional activity and increases stress sensitivity.
- CK2 phosphorylates Msn2 at Ser194 and Ser638; mutation of Ser638 impairs Msn2 activity and stress tolerance.
- CK2 influences Msn2 nuclear retention, but not its import/export patterns, suggesting a role beyond direct phosphorylation.
Conclusions:
- CK2-dependent phosphorylation is essential for activating the general stress response in yeast.
- CK2 regulates Msn2/4 activity through direct phosphorylation and potentially by modulating cellular translocation machinery.
- CK2 plays a critical role in yeast stress adaptation and survival.
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