In the fission yeastSchizosaccharomyces pombethe 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 proteinphosphorylation. Cells ofS. pombesubjected tocold shock (transfer from 28 Cto15 C) transiently activated the Sty1p mitogen-activated protein kinase (MAPK) by phosphorylation.