Isolation, Sequencing, and Disruption of the CKA1 Gene Encoding the Alpha Subunit of Yeast Casein Kinase II

Abstract

Casein kinase II of Saccharomyces cerevisiae contains two distinct catalytic subunits, alpha and alpha′, which must be encoded by separate genes (R. Padmanabha and C. V. C. Glover, J. Biol. Chem. 262:1829-1835, 1987). The gene encoding the 42-kilodalton alpha subunit has been isolated by screening a yeast genomic library with oligonucleotide probes synthesized on the basis of the N-terminal amino acid sequence of the polypeptide. This gene (designated CKA1) contains an intron-free open reading frame of 372 amino acid residues. The deduced amino acid sequence is 67% identical to the alpha subunit of Drosophila melanogaster casein kinase II. The CKA1 gene product appears to be distantly related to other known protein kinases but exhibits highest similarity to the CDC28 gene product and its homolog in other species. Gene replacement techniques have been used to generate a null cka1 mutant allele. Haploid and diploid strains lacking a functional CKA1 gene appear to be phenotypically wild type, presumably because of the presence of the alpha′ gene. Interestingly, the CKA1 gene appears to be single copy in the yeast genome; i.e., the alpha′ gene, whose existence is known from biochemical studies and protein sequencing, cannot be detected by low-stringency hybridization.