It is suggested that EWS-POU5F1 may act as an oncogenic transcription factor and that its expression may contribute to undifferentiated and immature phenotypes of BST..     ///    The EWSR1-POU5F1 chimera consists of exons 1-6 of EWSR1 and exons 2-5 and a part of exon 1 of POU5F1. 