EWS, BUT NOT EWS-FLI-1, IS ASSOCIATED WITH BOTH TFIID AND RNA-POLYMERASE-II - INTERACTIONS BETWEEN 2 MEMBERS OF THE TET FAMILY, EWS AND HTAF(II)68, AND SUBUNITS OF TFIID AND RNA-POLYMERASE-II COMPLEXES

The t(11;22) chromosomal translocation specifically linked to Ewing sa rcoma and primitive neuroectodermal tumor results in a chimeric molecu le fusing the amino-terminus-encoding region of the EWS gene to the ca rboxyl-terminal DNA-binding domain encoded by the FLI-1 gene. As the f unction of the protein encoded by the EWS gene remains unknown, we inv estigated the putative role of EWS in RNA polymerase II (Pol II) trans cription by comparing its activity with that of its structural homolog , hTAF(II)68. We demonstrate that a portion of EWS is able to associat e with the basal transcription factor TFIID, which is composed of the TATA-binding protein (TBP) and TBP-associated factors (TAF(II)s). In v itro binding studies revealed that both EWS and hTAF(II)68 interact wi th the same TFIID subunits, suggesting that the presence of EWS and th at of hTAF(II)68 in the same TFIID complex may be mutually exclusive. Moreover, EWS is not exclusively associated with TFIID but, similarly to hTAF(II)68, is also associated with the Pol II complex. The subunit s of Pol II that interact with EWS and hTAF(II)68 have been identified , confirming the association with the polymerase. In contrast to EWS, the tumorigenic EWS-FLI-1 fusion protein is not associated with either TFIID or Pol II in Ewing cell nuclear extracts. These observations su ggest that EWS and EWS-FLI-1 may play different roles in Pol II transc ription.