Cold induces stress‐activated protein kinase‐mediated response in the fission yeast Schizosaccharomyces pombe

Abstract

In the fission yeast Schizosaccharomyces pombe the Wak1p/ Win1p-Wis1p-Sty1p stress-activated protein kinase (SAPK) pathway relays environmental signals to the transcriptional machinery and modulates gene expression via a cascade of protein phosphorylation. Cells of S. pombe subjected to cold shock (transfer from 28°C to 15°C) transiently activated the Sty1p mitogen-activated protein kinase (MAPK) by phosphorylation. Induction of this response was completely abolished in cells disrupted in the upstream response regulator Mcs4p. The cold-triggered Sty1p activation was partially dependent on Wak1p MAPKKK and fully dependent on Wis1p MAPKK suggesting that the signal transmission follows a branched pathway, with the redundant MAPKKK Win1p as alternative transducer to Wis1p, which subsequently activates the effector Sty1p MAPK. Also, the bZIP transcription factor Atf1p became phosphorylated in a Sty1p-dependent way during the cold shock and this phosphorylation was found responsible for the increased expression of gpd1 + , ctt1 + , tps1 + and ntp1 + genes. Strains deleted in transcription factors Atf1p or Pcr1p were unable to grow upon incubation at low temperature whereas those disrupted in any member of the SAPK pathway were able to do so. These data reveal that S. pombe responds to cold by inducing the SAPK pathway. However, such activation is dispensable for yeast growth in cold conditions, supporting that the presence of Atf1/Pcr1 heterodimers, rather than an operative SAPK pathway, is critical to ensure yeast growth at low temperature by an as yet undefined mechanism.Keywords: cold; SAPK pathway; fission yeast.Low temperature is an important environmental signal for all living organisms. Adaptive response to cold stress involves synthesis of several types of proteins. In bacteria, thermal downshifts induce cold-shock proteins (Csp) that function as RNA chaperones favouring efficient translation of mRNAs at low temperature [1]. However, in eukaryotes no proteins homologous to bacterial Csp's have been isolated and cold shock-inducible proteins range from structural components involved in ribosomal biogenesis to transcriptional regulation factors that activate gene expression in response to a drop in temperature [2,3].The mitogen-activated protein kinase (MAPK) signalling pathways are critical for the sensing and response of eukaryotic cells to changes in the external environment [4]. These MAPK cascades are highly conserved through evolution and serve to transduce signals to the nucleus, which result in new patterns of gene expression [5,6]. Each MAPK module comprises at least three protein kinases: a MAP kinase is activated through phosphorylation on specific threonine and tyrosine residues by a MAPK kinase (MAPKK or MEK) which is in turn activated by phosphorylation in one or several serine and threonine residues by a MAPKK kinase (MAPKKK or MEKK). Recently, different studies have revealed a key role for MAPK cascades in the response of metazoan cells to osmotic changes, heat shock, oxidative stress and UV radi...

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“…Trehalose has a dual function as a storage carbohydrate and a stress protection metabolite (Kwon et al, 2003;Thevelein, 1996). Transcriptional levels of TPS1 and TPS2 are increased by heat shock, cold or ethanol stress, salt stress, nutrient starvation, and other osmotic stresses (Winderickx et al, 1996;Wolschek & Kubicek, 1997;Soto et al, 2002;Pereira et al, 2001). Improving stress tolerance is a major goal in agriculture.…”

Molecular mechanism of human Nrf2 activation and degradation: Role of sequential phosphorylation by protein kinase CK2

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The Pbs2 MAP kinase kinase is essential for the oxidative-stress response in the fungal pathogen Candida albicans

“…In fission yeast, a functional-homologue route to the HOG pathway is mediated by the Sty1 MAP kinase, which responds to several stresses, such as heat and cold shock and osmotic and oxidative stress (Samejima et al, 1997; Shiozaki Russell, 1996;Soto et al, 2002). sty1 2 mutants are sterile and exhibit a G 2 cell-cycle delay, indicating additional roles for Sty1 in meiosis and cell-cycle progression (Millar, 1999;Shiozaki & Russell, 1995.…”

“…& Russell, 1996;Soto et al, 2002). sty1 2 mutants are sterile and exhibit a G 2 cell-cycle delay, indicating additional roles for Sty1 in meiosis and cell-cycle progression (Millar, 1999;Shiozaki & Russell, 1995.…”

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