Casein kinase II from Caenorhabditis elegans: Cloning, characterization, and developmental regulation of the gene encoding the β subunit

Complementary DNAs encoding the β subunit of casein kinase II (CKIIβ) from the nematode Caenorhabditis elegans were cloned and sequenced. The predicted β subunit polypeptide comprises 234 amino acid residues and has a M_r of 26,452. CKIIβ is not homologous with other types of proteins. In synchronously developing C. elegans the abundance of the 1.3-kilobase mRNA for CKIIβ varies in parallel with the level of mRNA encoding the catalytic subunit (α) of CKII. Thus, the developmental expression of CKII subunits is controlled coordinately and pretranslationally. CKIIβ and CKIIa mRN As 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 CKIIβ gene and an extensive 5′-flanking region was cloned and sequenced. The CKIIβ 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 CKIIβ mRNA is modified post-transcriptionally by trans-splicing with a leader sequence of 22 nucleotides. The CKIIβ gene was mapped to a position on C. elegans chromosome 2 that is in close proximity to the lin-11 gene.