The Schizosaccharomyces pombe pka1 gene, encoding a homolog of cAMP-dependent protein kinase

We have isolated 16 independent Schizosaccharomyces pombe cDNA clones that suppress the temperature-sensitive (ts) phenotype of a Saccharomyces cerevisiae strain containing the dominant-negative (ras2)^val19ala22 allele. Fourteen of these cDNAs encode Sz. pombe Rasl. The other two clones encode the C-terminal region of a protein we have named Pka1. We have cloned the pka1 gene from a Sz. pombe genomic library. It contains an uninterrupted open reading frame encoding a 512-amino-acid (aa) protein. The C-terminal region (aa 200-512) of Pka1 is 51-63% identical to cAMP-dependent protein kinase (Pka) catalytic subunits from other eukaryotes. Production of Pkal suppresses the ts phenotypes exhibited by Sa. cerevisiae ras1^-ras2^ts or cyr1^ts strains. Furthermore, overproduction of Pka1 in Sz. pombe results in a sterile phenotype and an abnormal morphology similar to that exhibited by cells in which the cAMP pathway is constitutively activated. These observations suggest that pka1 encodes the Sz. pombe Pka catalytic subunit.