Abstract
Control of the protein phosphorylation status is a major mechanism for regulation of cellular processes, and its alteration often lead to functional disorders. Ppz1, a protein phosphatase only found in fungi, is the most toxic protein when overexpressed in Saccharomyces cerevisiae. To investigate the molecular basis of this phenomenon, we carried out combined genome-wide transcriptomic and phosphoproteomic analyses. We have found that Ppz1 overexpression causes major changes in gene expression, affecting ~ 20% of the genome, together with oxidative stress and increase in total adenylate pools. Concurrently, we observe changes in the phosphorylation pattern of near 400 proteins (mainly dephosphorylated), including many proteins involved in mitotic cell cycle and bud emergence, rapid dephosphorylation of Snf1 and its downstream transcription factor Mig1, and phosphorylation of Hog1 and its downstream transcription factor Sko1. Deletion of HOG1 attenuates the growth defect of Ppz1-overexpressing cells, while that of SKO1 aggravates it. Our results demonstrate that Ppz1 overexpression has a widespread impact in the yeast cells and reveals new aspects of the regulation of the cell cycle.
Highlights
Control of the protein phosphorylation status is a major mechanism for regulation of cellular processes, and its alteration often lead to functional disorders
In addition to Ppz[1] inhibition, they associate with Cab[3], forming an unusual heterotrimeric phosphopantothenoylcysteine decarboxylase (PPCDC) enzyme[20,21,22], which catalyzes a fundamental step in the biosynthesis of coenzyme A (CoA)
Changes in transcriptomic profile induced by overexpression of Ppz[1]
Summary
Control of the protein phosphorylation status is a major mechanism for regulation of cellular processes, and its alteration often lead to functional disorders. Ppz[1], a protein phosphatase only found in fungi, is the most toxic protein when overexpressed in Saccharomyces cerevisiae. In Saccharomyces cerevisiae, the type 1-related Ser/Thr protein phosphatase Ppz[1] is a 692-residue protein composed of a C-terminal catalytic domain and a long N-terminal segment (≈ 350 residues). Ppz[1] has an important role in monovalent cation homeostasis, and deletion of PPZ1 results in increased salt tolerance[6] This effect has been attributed to a role of Ppz[1] in two different cellular processes: (i) the negative control of K + uptake through the high-affinity Trk transporters, and ii) a repressive effect on expression of the ENA1 gene, encoding a N a+/K+-ATPase involved in the response to salt s tress[6,7,8,9]. A double hal[3] vhs[3] mutant is not viable because of the inability to synthetize CoA19,20
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