New alternatively spliced variants of calmodulin-dependent protein kinase II from rabbit liver

Polymerase chain reaction analysis revealed four alternatively spliced variants of each of the γ and δ isoforms of calmodulin-dependent protein kinase II (CaM-kinase II) in rabbit liver. Among the four variants of the γ isoform, two were novel ones, designated as CaM-kinase II γ-H and γ-I. The γ-I variant possessed both of the two deletable exons, D2a and D2b, which had never been found together in any variant. Sequence analysis of the γ-I indicated that the D2a was upstream of the D2b and that they were contiguous with each other in the γ-I. Among the four variants of the δ isoform, two were also novel ones, designated as CaM-kinase II δ-11 and δ-12, and the other two were the already-reported ones, δ-2 and δ-6. The δ-11 and δ-12 were identical to the δ-2 and δ-6, respectively, except that three bases (CAG) located at a splicing junction was deleted in the δ-11 and δ-12, suggesting two splicing sites of a single intron. Thus, the diverse splicing patterns may produce many more variants than those so far considered.