SRp30a (ASF/SF2) regulates the alternative splicing of caspase-9 pre-mRNA and is required for ceramide-responsiveness.
Two splice variants are derived from the caspase-9 gene, proapoptotic caspase-9a and antiapoptotic caspase-9b, by either the inclusion or exclusion of an exon 3, 4, 5, and 6 cassette. Previous studies from our laboratory have shown that the alternative splicing of caspase-9 and the phosphorylation status of SR proteins, a conserved family of splicing factors, are regulated by chemotherapy and ceramide via the action of protein phosphatase-1. In this study, a link between ceramide, SR proteins, and the alternative splicing of caspase-9 was established. The downregulation of SRp30a in A549 cells by RNA interference technology resulted in an increase in the caspase-9b splice variant, with a concomitant decrease in the caspase-9a splice variant, thereby significantly decreasing the caspase-9a/9b ratio from 1.67 +/- 0.11 to 0.56 +/- 0.08 (P < 0.005). The specific downregulation of SRp30a also inhibited the ability of exogenous ceramide treatment to induce the inclusion of the exon 3, 4, 5, and 6 cassette. Therefore, we have identified SRp30a as an RNA trans-acting factor that functions as a major regulator of caspase-9 pre-mRNA processing and is required for ceramide to mediate the alternative splicing of caspase-9.
Massiello
Autumn
A
Department of Biochemistry, Virginia Commonwealth University, Richmond, 23298, USA.
Chalfant
Charles E
CE
D017398:Alternative Splicing / Q000187:drug effects*; D053453:Caspase 9; D020169:Caspases / Q000235:genetics*; D002518:Ceramides / Q000494:pharmacology*; D015536:Down-Regulation; D006801:Humans; D009687:Nuclear Proteins / Q000502:physiology*; D012322:RNA Precursors / Q000235:genetics*; D034741:RNA, Small Interfering / Q000235:genetics; D016601:RNA-Binding Proteins; D000068103:Serine-Arginine Splicing Factors
D002518:Ceramides; D009687:Nuclear Proteins; D012322:RNA Precursors; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D000068103:Serine-Arginine Splicing Factors; C506433:CASP9 protein, human; D053453:Caspase 9; D020169:Caspases