THE EXON SEQUENCE TAGG CAN INHIBIT SPLICING

The fibroblast growth factor receptor-2 gene contains a pair of altern ative exons, K-SAM and BEK, which are spliced in a cell type specific manner, We have shown previously that a 10 nucleotide sequence within the K-SAM exon exerts a negative effect on K-SAM exon splicing indepen dent of cell type, We demonstrate here that this sequence works autono mously, as it can repress splicing of a heterologous exon, the EIIIb a lternative exon of the rat fibronectin gene, By introducing point muta tions into the 10 nucleotide sequence, we have shown that the function al portion is limited to 4 nucleotides, TACO, the dinucleotide AG of w hich is particularly important. This short sequence may participate in the control of splicing of exons carrying it, provided that they carr y weak splice sites.