CASEIN KINASE-II FROM CAENORHABDITIS-ELEGANS - CLONING, CHARACTERIZATION, AND DEVELOPMENTAL REGULATION OF THE GENE ENCODING THE BETA SUBUNIT

Complementary DNAs encoding the beta-subunit of casein kinase II (CKII-beta) from the nematode Caenorhabditis elegans were cloned and sequenced. The predicted beta-subunit polypeptide comprises 234 amino acid residues and has a M(r) of 26,452. CKII-beta is not homologous with other types of proteins. In synchronously developing C. elegans the abundance of the 1.3-kilobase mRNA for CKII-beta varies in parallel with the level of mRNA encoding the catalytic subunit (alpha) of CKII. Thus, the developmental expression of CKII subunits is controlled coordinately and pretranslationally. CKII-beta and CKII-alpha mRNAs are enriched 5-10-fold in C. elegans embryos relative to their concentrations at several other stages of nematode development. A 3.8-kilobase pair segment of C. elegans DNA that contains the CKII-beta gene and an extensive 5'-flanking region was cloned and sequenced. The CKII-beta gene is divided into 6 exons by introns ranging from 49 to 533 base pairs in length. The first exon encodes 88 nucleotides of 5'-untranslated mRNA. Exon 2 (72 base pairs) contains the initiator Met codon and only 5 additional codons. Exons 3-6 encode 52, 63, 64, and 49 amino acid residues, respectively. The 5' terminus of CKII-beta mRNA is modified post-transcriptionally by trans-splicing with a leader sequence of 22 nucleotides. The CKII-beta gene was mapped to a position on C. elegans chromosome 2 that is in close proximity to the lin-11 gene.