Novel isoform of the Xenopus tropicalis PKA catalytic alpha subunit: An example of alternative splicing

The cAMP-dependent protein kinase (PKA) plays key roles in the control of various aspects of eukaryotic cellular activities by phosphorylating several proteins and is multifunctional in nature. In the case of frog, Xenopus tropicalis, a gene encoding the PKA catalytic alpha subunit has been identified which encodes a single protein. Here we report the occurrence of N-terminal alternative splicing events in X. tropicalis tadpole that, in addition to generating a myristoylatable isoforms, also generate the non-myristoylated variant of the catalytic alpha subunit as has been reported in various other organisms. In addition to the already characterized exon 1, the 5′ untranslated region and first intron actually contains one more other exon, that is alternatively spliced on to exon 2 at the 5′ end of the pre-mRNA. This N-terminal alternative splicing occurs in combination with already characterized all internal exons. Thus, X. tropicalis tadpole expresses at least two different isoforms of the catalytic alpha subunit of PKA. The significance of this structural diversity in the family of PKA catalytic subunits is discussed.