Protein Phosphatase 2A in Saccharomyces cerevisiae: Effects on Cell Growth and Bud Morphogenesis

Abstract

We have cloned three genes for protein phosphatases in the yeast Saccharomyces cerevisiae. Two of the genes, PPH21 and PPH22, encode highly similar proteins that are homologs of the mammalian protein phosphatase 2A (PP2A), while the third gene, PPH3, encodes a new PP2A-related protein. Disruptions of either PPH21 or PPH22 had no effects, but spores disrupted for both genes produced very small colonies with few surviving cells. We conclude that PP2A performs an important function in yeast cells. A disruption of the third gene, PPH3, did not in itself affect growth, but it completely prevented growth of spores disrupted for both PPH21 and PPH22. Thus, PPH3 provides some PP2A-complementing activity which allows for a limited growth of PP2A-deficient cells. Strains were constructed in which we could study the phenotypes caused by either excess PP2A or total PP2A depletion. We found that the level of PP2A activity has dramatic effects on cell shape. PP2A-depleted cells develop an abnormal pear-shaped morphology which is particularly pronounced in the growing bud. In contrast, overexpression of PP2A produces more elongated cells, and high-level overexpression causes a balloonlike phenotype with huge swollen cells filled by large vacuoles.

Autophosphorylation−Inactivation Site of Hexokinase 2 in Saccharomyces cerevisiae

“…Finally, we note that reactivation of the autophosphorylated enzyme was achieved by the action of mammalian phosphoserine/phosphothreonine-specific protein phosphatase-2A (Figure 1B). The catalytic subunit of this enzyme is 80% identical to the protein phosphatase-2A-like proteins encodedby yeast genes PPH21 and PPH22 which are known to be essential in Saccharomyces cereVisiae (Ronne et al, 1991).…”

Carboxyl methylation of the phosphoprotein phosphatase 2A catalytic subunit promotes its functional association with regulatory subunits in vivo

“…Two highly homologous genes, PPH21 and PPH22 , redundantly encode the C subunit of PP2A (Sneddon et al ., 1990). Inactivation of both genes severely retards growth and analysis of temperature‐sensitive alleles has identified a requirement for PP2A in actin cytoskeletal organization and progression through mitosis (Ronne et al ., 1991; Lin and Arndt, 1995; Evans and Stark, 1997). Inactivation of PPH3 , a gene with homology to PPH21/22 , in a pph21 pph22 background is lethal, suggesting that Pph3 is a partially redundant isoform of C (Ronne et al ., 1991).…”

“…Inactivation of both genes severely retards growth and analysis of temperature‐sensitive alleles has identified a requirement for PP2A in actin cytoskeletal organization and progression through mitosis (Ronne et al ., 1991; Lin and Arndt, 1995; Evans and Stark, 1997). Inactivation of PPH3 , a gene with homology to PPH21/22 , in a pph21 pph22 background is lethal, suggesting that Pph3 is a partially redundant isoform of C (Ronne et al ., 1991). CDC55 and RTS1 encode proteins homologous to the mammalian B and B′ regulatory subunits, respectively (Healy et al ., 1991; Shu et al ., 1997).…”

Phosphorylation and Inactivation of Yeast 6-Phosphofructo-2-kinase Contribute to the Regulation of Glycolysis under Hypotonic Stress

“…A substantial but incomplete reactivation of PKC phosphorylated PFK2his was achieved by mammalian PP2A (Figure 2B). The catalytic subunit of the mammalian PP2A is 80% identical to the yeast protein phosphatases encoded by yeast genes PPH21 and PPH22 (24).…”