THE EWS ATF1 FUSION PROTEIN CONTAINS A DISPERSED ACTIVATION DOMAIN THAT FUNCTIONS DIRECTLY/

Naturally occurring chromosomal fusion of the Ewings Sarcoma Oncogene (EWS) to distinct cellular transcription factors, produces aberrant tr anscriptional activators that function as dominant oncogenes, In Malig nant Melanoma of Soft Parts the N-terminal region of EWS is fused to C -terminal region of the cAMP-inducible transcription factor ATF1. The EWS/ATF1 fusion protein binds to ATF sites present in cAMP-responsive promoters via the ATF1 bZIP domain and activates transcription constit utively in a manner that is dependent on an activation domain (EAD) pr esent in EWS. To further define the requirements for transactivation w e have performed mutational analysis of EWS/ATF1 in mammalian cells an d report several new findings. First, trans-activation by EWS/ATF1 doe s not require dimerisation with other ATF family members present in ma mmalian cells. Second, in contrast to the earlier suggestion of an all osteric role, the EAD can act directly. Third, determinants of trans-a ctivation are dispersed throughout the EAD and cooperate synergistical ly to produce potent trans-activation. We also report that the region of EWS containing the EAD can activate transcription in Yeast, This la tter finding might enable a genetic approach to understanding the mech anism of transcriptional activation by EWS and development of high-thr oughput screens for EWS inhibitors.