Presence of new alternative exons in human and mouse Fli-1 genes

The mouse Fli-1 proto-oncogene is activated by proviral integration of four murine leukemia retroviruses and its human counterpart is translocated (11 ,22) in Ewing tumors. We have identified two alternative exons 1 by RACE an alysis from a human neuroectodermal tumor. Exons la and Ib are located resp ectively 1.3 and 2.5 kb upstream from the published exon 1. Translation of these alternative messengers is predicted to generate very similar proteins . The sequence upstream from exon Ib showed functional promoter activity. E xon Ib was not conserved in the mouse but was detected in every analyzed hu man cell, whereas exon la was present only in a subset of them and also in various mouse cell lines. These results suggest that both mouse and human F li-1 gene expression might be under the control of several independent prom oter regions. (C) 2000 Elsevier Science B.V. All rights reserved.