PKC zeta controls DNA topoisomerase-dependent human caspase-2 pre-mRNA splicing

Caspase-2 exists as two main isoforms: the caspase-2L long isoform, which is pro-apoptotic, and the caspase-2S short isoform, which may be anti-apoptotic. Topoisomerase inhibitors drive inclusion of exon 9, specific for Casp-2S mRNA, and lower Casp-2S mRNA and protein. With cell lines engineered to express various PKC isoforms, we demonstrate that PKC zeta, but not PKCalpha, positively regulates Casp-2S mRNA assembly triggered by topoisomerase inhibitors. In addition, exon 9 inclusion is lowered in mitosis but increased in the G1/S phase. Hence, the control of caspase-2 exon 9 inclusion by topoisomerase inhibitors depends on phosphorylation and/or dephosphorylation events, and on the cell cycle phase.