title: Distinct subsets of Sit4 holophosphatases are required for inhibition of Saccharomyces cerevisiae growth by rapamycin and zymocin.
abstract: Protein phosphatase Sit4 is required for growth inhibition of Saccharomyces cerevisiae by the antifungals rapamycin and zymocin. Here, we show that the rapamycin effector Tap42, which interacts with Sit4, is dispensable for zymocin action. Although Tap42 binding-deficient sit4 mutants are resistant to zymocin, these mutations also block interaction between Sit4 and the Sit4-associating proteins Sap185 and Sap190, previously shown to mediate zymocin toxicity. Among the four different SAP genes, we found that SAP190 deletions specifically induce rapamycin resistance but that this phenotype is reversed in the additional absence of SAP155. Similarly, the rapamycin resistance of an rrd1Delta mutant lacking the Sit4 interactor Rrd1 specifically requires the Sit4/Sap190 complex. Thus, Sit4/Sap190 and Sit4/Sap155 holophosphatases apparently play opposing roles following rapamycin treatment, although rapamycin inhibition is operational in the absence of all Sap family members or Sit4. We further identified a Sit4-interacting region on Sap185 in sap190Delta cells that mediates Sit4/Sap185 complex formation and is essential for dephosphorylation of Elp1, a subunit of the Elongator complex. This suggests that Sit4/Sap185 and Sit4/Sap190 holophosphatases promote Elongator functions, a notion supported by data showing that their inactivation eliminates Elongator-dependent processes, including tRNA suppression by SUP4 and tRNA cleavage by zymocin.
authors.affiliation: Institut für Biologie, Bereich Genetik, Martin-Luther-Universität, Halle-Wittenberg, Weinbergweg 10, D-06120 Halle (Saale), Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Jablonowski
authors.forename: Jens-Eike
authors.initials: JE
authors.lastname: Täubert
authors.forename: Christian
authors.initials: C
authors.lastname: Bär
authors.forename: Michael J R
authors.initials: MJ
authors.lastname: Stark
authors.forename: Raffael
authors.initials: R
authors.lastname: Schaffrath
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism; D015536:Down-Regulation; D025141:Drug Resistance, Fungal; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects; D055646:Killer Factors, Yeast / Q000494:pharmacology*; D011485:Protein Binding / Q000187:drug effects; D054648:Protein Phosphatase 2 / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics / Q000254:growth & development*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D020123:Sirolimus / Q000494:pharmacology*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D055646:Killer Factors, Yeast; D029701:Saccharomyces cerevisiae Proteins; C100984:TAP42 protein, S cerevisiae; C058975:zymocin; D054648:Protein Phosphatase 2; C104343:SIT4 protein, S cerevisiae; D020123:Sirolimus