Browsing by Subject "fission yeast"

Now showing 1 - 4 of 4
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    Fission Yeast Receptor of Activated C Kinase (RACK1) Ortholog Cpc2 Regulates Mitotic Commitment through Wee1 Kinase
    (American Society for Biochemistry and Molecular Biology, 2010-10-25) Núñez, Andrés; Franco, Alejandro; Soto, Teresa; Vicente, Jero; Cansado Vizoso, José; Genética y Microbiología
    In the fission yeast Schizosaccharomyces pombe, Wee1-dependent inhibitory phosphorylation of the highly conserved Cdc2/Cdk1 kinase determines the mitotic onset when cells have reached a defined size. The receptor of activated C kinase (RACK1) is a scaffolding protein strongly conserved among eukaryotes which binds to other proteins to regulate multiple processes in mammalian cells, including the modulation of cell cycle progression during G1/S transition. We have recently described that Cpc2, the fission yeast ortholog to RACK1, controls from the ribosome the activation of MAPK cascades and the cellular defense against oxidative stress by positively regulating the translation of specific genes whose products participate in the above processes. Intriguingly, mutants lacking Cpc2 display an increased cell size at division, suggesting the existence of a specific cell cycle defect at the G2/M transition. In this work we show that protein levels of Wee1 mitotic inhibitor are increased in cells devoid of Cpc2, whereas the levels of Cdr2, a Wee1 inhibitor, are down-regulated in the above mutant. On the contrary, the kinetics of G1/S transition was virtually identical both in control and Cpc2-less strains. Thus, our results suggest that in fission yeast Cpc2/RACK1 positively regulates from the ribosome the mitotic onset by modulating both the protein levels and the activity of Wee1. This novel mechanism of translational control of cell cycle progression might be conserved in higher eukaryotes.
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    RNA-Binding Protein Rnc1 Regulates Cell Length at Division and Acute Stress Response in Fission Yeast through Negative Feedback Modulation of the Stress-Activated Mitogen-Activated Protein Kinase Pathway
    (American Society for Microbiology, 2020-02) Prieto-Ruíz, Francisco; Vicente-Soler, Jero; Franco Sánchez, Alejandro; Gómez-Gil, Elisa; Sánchez-Marinas, Marta; Vázquez-Marín, Beatriz; Aligué, Rosa; Madrid, Marisa; Moreno, Sergio; Soto, Teresa; Cansado Vizoso, José; Genética y Microbiología
    RNA-binding proteins (RBPs) play a major role during control of mRNA localization, stability, and translation and are central to most cellular processes. In the fission yeast Schizosaccharomyces pombe, the multiple K homology (KH) domain RBP Rnc1 downregulates the activity of the cell integrity pathway (CIP) via stabilization of pmp1 mRNA, which encodes the Pmp1 phosphatase that inactivates Pmk1, the mitogen-activated protein kinase (MAPK) component of this signaling cascade. However, Rnc1 likely regulates the half-life/stability of additional mRNAs. We show that Rnc1 downregulates the activity of Sty1, the MAPK of the stress-activated MAPK pathway (SAPK), during control of cell length at division and recovery in response to acute stress. Importantly, this control strictly depends on Rnc1’s ability to bind mRNAs encoding activators (Wak1 MAPKKK, Wis1 MAPKK) and downregulators (Atf1 transcription factor, Pyp1 and Pyp2 phosphatases) of Sty1 phosphorylation throughits KH domains. Moreover, Sty1 is responsible for Rnc1 phosphorylation in vivo at multiple phosphosites during growth and stress, and these modifications trigger Rnc1 for proper binding and destabilization of the above mRNA targets. Phosphorylation by Sty1 prompts Rnc1-dependent mRNA destabilization to negatively control SAPK signaling, thus revealing an additional feedback mechanism that allows precise tuning of MAPK activity during unperturbed cell growth and stress.
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    Solubilization and characterization of a cell wall-bound trehalase from ascospores of the fission yeast Schizosaccharomyces pombe
    (Jena : G. Fischer, 2009) Vicente, Jero; Soto, Teresa; Madrid, Marisa; Núñez, Andrés; Cansado Vizoso, José; Gacto, Mariano; Genética y Microbiología
    The genome of the fission yeast Schizosaccharomyces pombe lacks sequence homologs to ath1 genes coding for acid trehalases in other yeasts or filamentous fungi. However, acid trehalase activity is present at the spore stage in the life cycle of the fission yeast. The enzyme responsible for this activity behaves as a surface enzyme covalently linked to the spore cell walls in both wild-type and ntp1 mutant strains devoid of neutral trehalase. Lytic treatment of particulated cell wall fractions allowed the solubilization of the enzyme into an active form. We have characterized this soluble enzyme and found that its kinetic parameters, optimum pH and temperature, thermal denaturation and salt responses are closely similar to other conventional acid trehalases. Hence, this rather unusual enzyme can be recognized as acid trehalase by its biochemical properties although it does not share genetic homology with other known acid trehalases. The potential role of such acid trehalase in the mobilization of trehalose is discussed.
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    Stress-activated protein kinase-mediated down-regulation of the cell integrity pathway mitogen-activated protein kinase Pmk1p by protein phosphatases
    (American Society for Cell Biology, 2007-08-29) Madrid, Marisa; Núñez, Andrés; Soto, Teresa; Vicente, Jero; Gacto, Mariano; Cansado Vizoso, José; Genética y Microbiología
    Fission yeast mitogen-activated protein kinase (MAPK) Pmk1p is involved in morphogenesis, cytokinesis, and ion homeostasis as part of the cell integrity pathway, and it becomes activated under multiple stresses, including hyper- or hypotonic conditions, glucose deprivation, cell wall-damaging compounds, and oxidative stress. The only protein phosphatase known to dephosphorylate and inactivate Pmk1p is Pmp1p. We show here that the stress-activated protein kinase (SAPK) pathway and its main effector, Sty1p MAPK, are essential for proper deactivation of Pmk1p under hypertonic stress in a process regulated by Atf1p transcription factor. We demonstrate that tyrosine phosphatases Pyp1p and Pyp2p, and serine/threonine phosphatase Ptc1p, that negatively regulate Sty1p activity and whose expression is dependent on Sty1p-Atf1p function, are involved in Pmk1p dephosphorylation under osmostress. Pyp1p and Ptc1p, in addition to Pmp1p, also control the basal level of MAPK Pmk1p activity in growing cells and associate with, and dephosphorylate Pmk1p both in vitro and in vivo. Our results with Ptc1p provide the first biochemical evidence for a PP2C-type phosphatase acting on more than one MAPK in yeast cells. Importantly, the SAPK-dependent down-regulation of Pmk1p through Pyp1p, Pyp2p, and Ptc1p was not complete, and Pyp1p and Ptc1p phosphatases are able to negatively regulate MAPK Pmk1p activity by an alternative regulatory mechanism. Our data also indicate that Pmk1p phosphorylation oscillates as a function of the cell cycle, peaking at cell separation during cytokinesis, and that Pmp1p phosphatase plays a main role in regulating this process.