Two novel protein kinase C-related genes of fission yeast are essential for cell viability and implicated in cell shape control.

Two novel protein kinase C (PKC)-like genes, pck1+ and pck2+ were isolated from fission yeast by PCR. Both contain common domains of PKC-related molecules, but lack a putative Ca(2+)-binding domain so that they may belong to the nPKC group. Gene disruption of pck1+ and pck2+ establishes that they share an overlapping essential function for cell viability. Cells of a single pck2 deletion display severe defects in cell shape; they are irregular and sometimes pear-like instead of cylindrical. In contrast, the induced overexpression of pck2+ is lethal, producing multiseptated and branched cells. These results suggest that fission yeast PKC-like genes are involved in the polarity of cell growth control. We show that pck2 is allelic to sts6, a locus we have previously identified by its supersensitivity to staurosporine, a potent protein kinase inhibitor [Toda et al. (1991) Genes Dev., 5, 60-73]. In addition, the lethal overexpression of pck2+ can be suppressed by staurosporine, indicating that fission yeast pck1 and pck2 are molecular targets of this inhibitor.