THE EWS GENE, INVOLVED IN EWING FAMILY OF TUMORS, MALIGNANT-MELANOMA OF SOFT PARTS AND DESMOPLASTIC SMALL ROUND-CELL TUMORS, CODES FOR AN RNA-BINDING PROTEIN WITH NOVEL REGULATORY DOMAINS

The EWS gene, which maps to band q12 of human chromosome 22, is involv ed in a wide variety of human solid tumors including Ewing sarcoma, re lated primitive neuroectodermal tumors, malignant melanoma of soft par ts and desmoplastic small round cell tumors. In these tumors, the EWS is fused to genes encoding transcriptional activators/repressors, like Fli-1 or erg or ATF 1 or wt1. To better understand the function of th e EWS protein, we cloned the EWS cDNA. Sequence analysis of this cDNA revealed differential splicing invoving two exons encoding 72 amino ac ids. Both alternatively spliced transcripts, EWS and EWS-b, are expres sed in a variety of cells. Because EWS proteins contain putative conse rved RNA binding motifs, we studied the RNA binding properties of the EWS protein. The EWS-b protein binds to RNA in vitro and, specifically , to poly G and poly U. The RNA binding activity was localized to the carboxy terminal 86 amino acids, which constitute RGG box. Thus the am ino terminal domain of EWS (NTD-EWS), which is involved in chromosome translocation may regulate the specificity of RNA binding activity of EWS. An EWS-erg chimeric protein, which is found in Ewing's sarcoma ce lls, functions as a transcriptional activator. Mutational analysis of EWS-erg chimeric protein revealed that NTD-EWS functions as a regulato ry domain for the transcriptional activation properties of EWS-erg chi meric protein.