No abstract

Recent studies have shown that global gene expression during oxidative stress in Schizosaccharomyces pombe is regulated by stress-induced activation and binding of Csx1 to atf1 + mRNA. However, the kinase responsible for the activation of Csx1 has not been identified. Here, we describe, for the first time, that Csx1 is phosphorylated by S. pombe LAMMER kinase, Lkh1, under oxidative conditions and that the stressactivated binding of the Csx1 to the atf1 + mRNA was also affected by Lkh1 and Spc1. These data indicate that concerted actions of Spc1 and Lkh1 are required for the activation of Csx1 during oxidative condition in the fission yeast S. pombe.

The cation-dependent galactose-specific flocculation activity of the Schizosaccharomyces pombe null mutant of lkh1+, the gene encoding LAMMER kinase homolog, has previously been reported by our group. Here, we show that disruption of prk1+, another flocculation associated regulatory kinase encoding gene, also resulted in cation-dependent galactose-specific flocculation. Deletion of prk1 increased the flocculation phenotype of the lkh1+ null mutant and its overexpression reversed the flocculation of cells caused by lkh1 deletion. Transcript levels of prk1+ were also decreased by lkh1+ deletion. Cumulatively, these results indicate that Lkh1 is one of the negative regulators acting upstream of Prk1, regulating non-sexual flocculation in fission yeast.