THE EWINGS-SARCOMA EWS FLI-1 FUSION GENE ENCODES A MORE POTENT TRANSCRIPTIONAL ACTIVATOR AND IS A MORE POWERFUL TRANSFORMING GENE THAN FLI-1/

EWS/FLI-1 is a chimeric protein formed by a tumor-specific 11;22 trans location found in both Ewing's sarcoma and primitive neuroectodermal t umor of childhood. EWS/FLI-1 has been shown to be a potent transformin g gene, suggesting that it plays an important role in the genesis of t hese human tumors. We now demonstrate that EWS/FLI-1 has the character istics of an aberrant transcription factor. Subcellular fractionation experiments localized the EWS/FLI-1 protein to the nucleus of primitiv e neuroectodermal tumor cells. EWS/FLI-1 specifically bound in vitro a n ets-2 consensus sequence similarly to normal FLI-1. When coupled to a GAL4 DNA-binding domain, the amino-terminal EWS/FLI-1 region was a m uch more potent transcriptional activator than the corresponding amino -terminal domain of FLI-1. Finally, EWS/FLI-1 efficiently transformed NIH 3T3 cells, but FLI-1 did not. These data suggest that EWS/FLI-1, f unctioning as a transcription factor, leads to a phenotype dramaticall y different from that of cells expressing FLI-1. EWS/FLI-1 could disru pt normal growth and differentiation either by more efficiently activa ting FLI-1 target genes or by inappropriately modulating genes normall y not responsive to FLI-1.