BAX EXON 2 CONTAINS A CRITICAL ACCEPTOR SITE FOR ALTERNATIVE SPLICING OF THE BAXΔ2 ISOFORM BY SAMUEL KISSINGER Submitted in partial fulfillment of the requirements for
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Previous studies have revealed that BAXΔ2, an alternatively spliced form of BAX with a microsatellite mutation (G8 to G7) on BAX exon 3, is a more potent inducer of cell death and a potential means of treatment for cancers with microsatellite instability (MSI). To define the critical splicing points for the splicing of the BAXΔ2 isoform, BAX mini-gene constructs with GFP reporter genes were used for site directed mutagenesis based disruption of predicted critical splicing points. The mutant constructs were transfected into mammalian cells, and expression of BAX-GFP fusion proteins were examined by both fluorescence microscopy and Western blot analysis. Our results indicate that the BAX exon 2 A667T mutation could completely abolish generation of the BAXΔ2 isoform. These results suggest that the acceptor site AG in BAX exon 2 position 667 is critical for alternative splicing to the BAXΔ2 isoform in microsatellite unstable BAX G7 tumor cells.