EXON SEQUENCE IS REQUIRED FOR REGULATED RNA SPLICING OF THE HUMAN FIBROBLAST-GROWTH-FACTOR RECEPTOR-1 ALPHA-EXON

Alternative RNA processing of the human fibroblast growth factor recep tor-1 transcript results in receptor forms that vary in their affinity for fibroblast growth factor. An alternative RNA processing event inv olving recognition of the alpha-exon is deregulated during neoplastic transformation of glial cells. We have previously established a splici ng reporter/transfection cell culture model system to identify sequenc es involved in recognition of this exon. In this study, the system was used to identify two sequence elements that differentially function t o regulate splicing of this exon. Exclusion of the alpha-exon in gliob lastoma cells specifically required the downstream intron sequence com prising the 5'-splice site. Replacement or mutation of this sequence i ncreasing complementarity to U1 RNA resulted in enhanced exon recognit ion in SNB-19 glioblastoma cells. Sequences within the exon were found to be required for alpha-exon inclusion. Deletion and gain-of-functio n experiments identified a 69-nucleotide exon sequence that was specif ically required for alpha-exon inclusion. These studies indicate that multiple sequences are required for the regulated recognition of the a lpha-exon.