In a study by Scotlandi et al., 2000, was found that a minor population of cells from giant cell tumour of bone samples had an EWSR1/FLI1 transcript, but this was found in a high percentage of samples (13/15).

FLI1 (Friend leukemia virus integration 1)

11q24.3

From N-term to C-term: a 5 ETS domain, a Fli-1-specific transcriptional activation domain, and a 3 ETS transcriptional activation domain. Member of ETS transcription factor gene family. FLI1 binds to DNA in a sequence-specific manner.

EWSR1 (Ewing sarcoma breakpoint region 1)

22q12.2

From N-term to C-term: a transactivation domain (TAD) containing multiple degenerate hexapeptide repeats, 3 arginine/glycine rich domains (RGG regions), a RNA recognition motif, and a RanBP2 type Zinc finger. Role in transcriptional regulation for specific genes and in mRNA splicing.

5 EWSR1 - 3 FLI1. EWSR1 exon 7 is fused in frame to FLI1 exon 6 and/or 5 (type 1 and type 2 fusions respectively), indicating, when both transcripts were produced in a given sample, genetic heterogeneity within the tumour.

Fusion of the N terminal transactivation domain of EWSR1 to the ETS type DNA binding domain of FLI1.