EWS/FLI alters 5 '-splice site selection

The chimeric gene EWS/FLI is present in at least 85% of Ewing's sarcomas as a result of chromosomal translocations, The resulting fusion protein conta ins the N terminus of the RNA-binding protein EWS and the ETS DNA-binding d omain of the transcription factor FLI-1, Although EWS/FLI binds DNA and act ivates transcription, both EWS and EWS/FLI also interact with SF1 and U1C, essential components of the splicing machinery. Therefore, we tested the ab ility of EWS and EWS/FLI to alter 5'-splice site selection using an E1A gen e in vivo splicing assay. We found that EWS/FLI, but not EWS, interfered wi th heterogeneous nuclear ribonucleoprotein Al-dependent splice site selecti on of E1A, Mutational analysis of EWS/FLI revealed that the ability to affe ct pre-mRNA splicing coincided with transforming activity. Therefore, EWS/F LI has the ability to influence splicing as well as transcription.