Different modulation of the outputs of yeast MAPK-mediated pathways by distinct stimuli and isoforms of the dual-specificity phosphatase Msg5
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The activity of protein phosphatases on mitogen-activated protein kinases (MAPKS) is essential in the modulation of the final outcome of MAPK-signalling pathways. The yeast dual-specificity phosphatase (DSP) Msg5, expressed as two isoforms of different length, dephosphorylates the MAPKs of mating and cell integrity pathways, Fus3 and Slt2, respectively, but its action on the MAPK Kss1 is unclear. Here we analyse the global impact of Msg5 on the yeast transcriptome. Both Fus3- and Slt2- but not Kss1-mediated gene expression is induced in cells lacking Msg5. However, although these cells show high Slt2 phosphorylation, the Rlm1-dependent Slt2-regulated transcriptional response is weak. Therefore, mechanisms concomitant with Slt2 phosphorylation are required for a strong Rlm1 activation. The limited Slt2 activity on Rlm1 is not a specific effect on this substrate but a consequence of its low kinase activity in msg5Δ cells. Lack of Msg5 does not increase Kss1 phosphorylation although both proteins physically interact. Both Msg5 isoforms interact similarly with Slt2, whereas the long form binds Fus3 with higher affinity and consequently down-regulates it more efficiently than the short one. We propose that specific binding of DSP isoforms to distinct MAPKs provides a novel mechanism for fine tuning different pathways by the same phosphatase.
KeywordsYeast Msg5 MAPK-phosphatase Fus3 Kss1 Slt2
We thank José Manuel Rodríguez-Peña, Victor J. Cid, María Jiménez-Sánchez, Raul García and Miguel Ángel Rodríguez-Gabriel for their helpful comments and reagents. We also thank M.I. García-Sáez, Rosa Pérez and Pedro Botías from Centro de Genómica y Proteómica de la Universidad Complutense/Parque Científico de Madrid (Spain) for DNA sequencing, Q-RT-PCR and microarray data analysis. This work was supported by grant BIO2007-67299 from Ministerio de Educación y Ciencia (Spain) and S-SAL-0246-2006 from Comunidad Autónoma de Madrid to M. Molina. M.J.M. is recipient of a FPU fellowship from Ministerio de Educación y Ciencia (Spain) and C.B. of a fellowship of the Universidad Complutense de Madrid (Spain).
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