Regulation of FAS exon definition and apoptosis by the ewing sarcoma protein

Paronetto, Maria Paola; Bernardis, Isabella; Volpe, Elisabetta; Bechara, Elias; Sebestyén, Endre; Eyras Jiménez, Eduardo; Valcárcel, J. (Juan)

doi:http://dx.doi.org/10.1016/j.celrep.2014.03.077

Regulation of FAS exon definition and apoptosis by the ewing sarcoma protein

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Paronetto MP, Bernardis I, Volpe E, Bechara E, Sebestyen E, Eyras E, Valcarcel J. Regulation of FAS exon definition and apoptosis by the ewing sarcoma protein. Cell Reports. 2014; 7: 1211-1226. DOI 10.1016/j.celrep.2014.03.077

Abstract

The Ewing sarcoma protein EWS is an RNA and DNA binding protein implicated in transcription, pre-mRNA splicing, and DNA damage response. Using CLIP-seq, we identified EWS RNA binding sites in exonic regions near 5′ splice sites. A prominent target was exon 6 of the FAS/CD95 receptor, which is alternatively spliced to generate isoforms with opposing activities in programmed cell death. Depletion and overexpression experiments showed that EWS promotes exon 6 inclusion and consequently the synthesis of the proapoptotic FAS/CD95 isoform, whereas an EWS-FLI1 fusion protein characteristic of Ewing sarcomas shows decreased activity. Biochemical analyses revealed that EWS binding promotes the recruitment of U1snRNP and U2AF65 to the splice sites flanking exon 6 and therefore exon definition. Consistent with a role for EWS in the regulation of programmed cell death, cells depleted of EWS show decreased sensitivity to FAS-induced apoptosis, and elevated EWS expression enhances apoptosis in EWS-haploinsufficient Ewing sarcoma cells.