The leukemia associated ETO nuclear repressor gene is regulated by the GATA-1 transcription factor in erythroid/megakaryocytic cells

A putative proximal ETO promoter was identified within 411 bp upstream of the transcription start site. Strong ETO promoter activity was specifically observed upon transfection of a promoter reporter construct into erythroid/megakaryocytic cells, which have endogeneous ETO gene activity. An evolutionary conserved region of 228 bp revealed potential cis-elements involved in transcription of ETO. Disruption of the evolutionary conserved GATA -636 consensus binding site repressed transactivation and disruption of the ETS1 -705 consensus binding site enhanced activity of the ETO promoter. The promoter was stimulated by overexpression of GATA-1 into erythroid/megakaryocytic cells. Electrophoretic mobility shift assay with erythroid/megakaryocytic cells showed specific binding of GATA-1 to the GATA -636 site. Furthermore, results from chromatin immunoprecipitation showed GATA-1 binding in vivo to the conserved region of the ETO promoter containing the -636 site. The results suggest that the GATA -636 site may have a role in activation of the ETO gene activity in cells with erythroid/megakaryocytic potential. Leukemia associated AML1-ETO strongly suppressed an ETO promoter reporter in erythroid/megakaryocytic cells.We demonstrate that the GATA-1 transcription factor binds and transactivates the ETO proximal promoter in an erythroid/megakaryocytic-specific manner. Thus, trans-acting factors that are essential in erythroid/megakaryocytic differentiation govern ETO expression.The human ETO co-repressor family comprises the homologous nuclear proteins ETO (Eight-Twenty-One), MTG16 (Myeloid Translocation Gene on chromosome 16) and MTGR1 (Myeloid translocation Gene-Related protein1) evolutionary related to the Drosophila protein Nervy [1]. The ETO homologues do not interact directly with DNA but are recruited by transcription factors such as PLZF, BCL6, TAL1/SCL, Gfi1and Heb [2-7] to become partners of multi-protein complexes on a gene promoter [8,9]. The ETO homologues of the c