Ref2, a regulatory subunit of the yeast protein phosphatase 1, is a novel component of cation homoeostasis.
Maintenance of cation homoeostasis is a key process for any living organism. Specific mutations in Glc7, the essential catalytic subunit of yeast protein phosphatase 1, result in salt and alkaline pH sensitivity, suggesting a role for this protein in cation homoeostasis. We screened a collection of Glc7 regulatory subunit mutants for altered tolerance to diverse cations (sodium, lithium and calcium) and alkaline pH. Among 18 candidates, only deletion of REF2 (RNA end formation 2) yielded increased sensitivity to these conditions, as well as to diverse organic toxic cations. The Ref2F374A mutation, which renders it unable to bind Glc7, did not rescue the salt-related phenotypes of the ref2 strain, suggesting that Ref2 function in cation homoeostasis is mediated by Glc7. The ref2 deletion mutant displays a marked decrease in lithium efflux, which can be explained by the inability of these cells to fully induce the Na+-ATPase ENA1 gene. The effect of lack of Ref2 is additive to that of blockage of the calcineurin pathway and might disrupt multiple mechanisms controlling ENA1 expression. ref2 cells display a striking defect in vacuolar morphogenesis, which probably accounts for the increased calcium levels observed under standard growth conditions and the strong calcium sensitivity of this mutant. Remarkably, the evidence collected indicates that the role of Ref2 in cation homoeostasis may be unrelated to its previously identified function in the formation of mRNA via the APT (for associated with Pta1) complex.
Ferrer-Dalmau
Jofre
J
Departament de Bioquímica i Biologia Molecular and Institut de Biotecnologia i Biomedicina, Universitat Autònoma de Barcelona, Barcelona 08193, Spain.
González
Asier
A
Platara
Maria
M
Navarrete
Clara
C
Martínez
José L
JL
Barreto
Lina
L
Ramos
José
J
Ariño
Joaquín
J
Casamayor
Antonio
A
D000222:Adaptation, Physiological / Q000187:drug effects; D000595:Amino Acid Sequence; D019703:Calcineurin / Q000235:genetics / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002122:Calcium Chloride / Q000494:pharmacology; D002412:Cations / Q000378:metabolism*; D006706:Homeostasis; D006863:Hydrogen-Ion Concentration; D017136:Ion Transport; D008094:Lithium / Q000378:metabolism; D018021:Lithium Chloride / Q000494:pharmacology; D009154:Mutation; D054645:Protein Phosphatase 1 / Q000235:genetics / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics / Q000378:metabolism
D002412:Cations; C086375:ENA1 protein, S cerevisiae; C092121:REF2 protein, S cerevisiae; D016601:RNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; D012965:Sodium Chloride; D008094:Lithium; D012964:Sodium; D019703:Calcineurin; C092048:GLC7 protein, S cerevisiae; D054645:Protein Phosphatase 1; D000254:Sodium-Potassium-Exchanging ATPase; D018021:Lithium Chloride; D002122:Calcium Chloride; D002118:Calcium