The MDS-Associated Protein EVI1 Impairs Erythroid and Megakaryocytic Differentiation by Direct Interaction with GATA-1.

EVI1 is an aggressive nuclear oncoprotein deregulated by recurring chromosomal abnormalities in acute myeloid leukemia and myelodysplastic syndrome. This protein has two Zn finger domains containing 7 motifs at the N-terminus and 3 motifs at the C-terminus. The expression of this gene is a very poor prognostic marker and is associated with diseases characterized by erythroid and megakaryocytic defects. We have recently shown that the forced expression of EVI1 in murine bone marrow results in a fatal disease with features characteristic of MDS, including fatal dyserythropoiesis, dysmegakaryopoiesis, and anemia. These lineages are regulated by the transcription factor GATA-1, a DNA-binding protein that in addition to erythrocytes and megakaryocytes exerts a strict control also on the differentiation of mast cells and eosinophils, on the basis of its expression and association with specific partners.

In the present study, we used biochemical assays and in vitro culture to show that GATA-1 and the N-terminus of EVI1 are involved in the formation of a protein complex that is unable to regulate efficiently GATA-1-dependent promoters in reporter gene assays. EMSA studies with a GATA-1-specific probe indicate that EVI1 does not recognize and bind to the DNA probe but disrupts the DNA-binding of GATA-1. By deletion analysis and point mutations, we mapped the interaction between the proteins to two motifs in the proximal Zn finger domain of EVI1 and to the C-terminus Zn finger of GATA-1. Cys to Ala mutations in the two EVI1 motifs abrogate the interaction and restore the response of a promoter in reporter gene assays. We propose that the association between EVI1 and the DNA-binding motif of GATA-1 impairs efficient promoter binding by GATA-1 and the regulation of erythroid and megakaryocytic lineage. There studies suggest that the interaction surface between the two proteins could be an attractive target for the development of competing small molecules as a treatment in EVI1-associated leukemia.