The FLI-1 and chimeric EWS-FLI-1 oncoproteins display similar DNA binding specificities.
Although recent data have demonstrated that the chimeric EWS-FLI-1 cDNA isolated from cases of Ewing's sarcoma can transform NIH 3T3 cells, little is known about the basis for this transformation. Since FLI-1 and EWS-FLI-1 contain an Ets domain, both proteins may act as sequence-specific transcription factors. Here the DNA binding properties of FLI-1 and EWS-FLI-1 have been examined. An epitope-tagging strategy was developed to determine the optimum DNA-binding sequence of FLI-1. The alignment of cloned binding sequences showed a consensus DNA-binding site of ACCGGAAG/aT/c. This consensus sequence shows greater specificity for sequence 5' of the GGAA core site than those of other Ets proteins. Using several truncated forms of FLI-1, we show that the Ets domain is necessary and sufficient for the DNA binding specificity of FLI-1. The EWS-FLI-1 protein displayed the same DNA binding specificity and affinity as FLI-1 did. Despite their DNA binding similarities, the EWS-FLI-1 translocation product is likely to have a distinct pattern of expression from that of FLI-1 since the translocation results in the replacement of the 5' regulatory region of Fli-1 with that of EWS. Consistent with this we found that Fli-1 mRNA expression in lymphocytes was high in quiescent cells and disappeared upon activation while EWS mRNA expression was low in resting cells and increased in activated T cells. In summary, our data suggest that EWS-FLI-1 might act through the same target genes normally regulated by FLI-1, and EWS-FLI-1-induced transformation may result from dysregulation of FLI-1 target genes during cell proliferation and differentiation.
Mao
X
X
Department of Microbiology/Immunology, University of Michigan Medical Center, Ann Arbor 48109.
Miesfeldt
S
S
Yang
H
H
Leiden
J M
JM
Thompson
C B
CB
D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D000939:Epitopes; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D011485:Protein Binding; D051789:Proto-Oncogene Protein c-fli-1; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012512:Sarcoma, Ewing / Q000235:genetics*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*
D004268:DNA-Binding Proteins; D000939:Epitopes; C497426:Fli1 protein, mouse; D051789:Proto-Oncogene Protein c-fli-1; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D004247:DNA