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Eukaryotic Cell doi:10.1128/EC.00358-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

The fission yeast MAP kinase Sty1 interacts with translation factors

Department of Cell and Molecular Biology, Lundberg Laboratory, Göteborg University, P.O. Box 462 SE-405 30 Göteborg, Sweden

^* To whom correspondence should be addressed. Email: Per.Sunnerhagen{at}cmb.gu.se.

	Abstract

Signaling by stress-activated MAP kinase pathways influences translation efficiency in mammalian cells and budding yeast. We have investigated the stress-activated MAP kinase from fission yeast, Sty1, and its downstream protein kinase Mkp1/Srk1, for physically associated proteins using TAP tagging. We find Sty1, but not Mkp1, to bind to the translation elongation factor eEF2 and the translation initiation factor eIF3a. The Sty1 – eIF3a interaction is weakened under oxidative or hyperosmotic stress, whereas the Sty1 – eEF2 interaction is stable. Nitrogen deprivation causes a transient strengthening both of the Sty1 – eEF2 and the Sty1 – Mkp1 interactions, overlapping with the time of maximal Sty1 activation. Analysis of polysome profiles from cells under oxidative stress, or after hyperosmotic shock or nitrogen deprivation, shows that translation in sty1 mutant cells recovers considerably less efficiently than in the wild-type. Cells lacking the Sty1-regulated transcription factor Atf1 are deficient in maintaining and recovering translational activity after hyperosmotic shock, but not during oxidative stress or nitrogen starvation. In cells lacking Sty1, eIF3a levels are decreased, and phosphorylation of eIF3a is reduced. Taken together, our data point at a central role in translational adaptation for the stress-activated MAP kinase pathway in fission yeast similar to other investigated eukaryotes, with the exception that fission yeast MAPK-activated protein kinases seem not to be directly involved in this process.