Organization and alternative splicing of the Caenorhabditis elegans cAMP-dependent protein kinase catalytic-subunit gene (kin-1)

The cAMP-dependent protein kinase (protein kinase A, PK-A) is multifunction al in nature, with key roles in the control of diverse aspects of eukaryoti c cellular activity. In the case of the free-living nematode, Caenorhabditi s elegans, a gene encoding the PK-A catalytic subunit has been identified a nd two isoforms of this subunit, arising from a C-terminal alternative-spli cing event, have been characterized [Gross, Bagchi, Lu and Rubin (1990) J. Biol. Chem. 265, 6896-6907]. Here we report the occurrence of N-terminal al ternative-splicing events that, in addition to generating a multiplicity of non-myristoylatable isoforms, also generate the myristoylated variant(s) o f the catalytic subunit that we have recently characterized [Aspbury, Fishe r, Rees and Clegg (1997) Biochem. Biophys. Res. Commun. 238, 523-527]. The gene spans more than 36 kb and is divided into a total of 13 exons. Each of the mature transcripts contains only 7 exons. In addition to the already c haracterized exon 1, the 5'-untranslated region and first intron actually c ontain 5 other exons, any one of which may be alternatively spliced on to e xon 2 at the 5' end of the pre-mRNA. This N-terminal alternative splicing o ccurs in combination with either of the already characterized C-terminal al ternative exons. Thus, C. elegans expresses at least 12 different isoforms of the catalytic subunit of PK-A. The significance of this unprecedented st ructural diversity in the family of PK-A catalytic subunits is discussed.