GATA-1 is essential for the generation of the erythroid, megakaryocytic, 
eosinophilic and mast cell lineages. It acts as an activator and repressor of 
different target genes, for example, in erythroid cells it represses cell 
proliferation and early hematopoietic genes while activating erythroid genes, 
yet it is not clear how both of these functions are mediated. Using a 
biotinylation tagging/proteomics approach in erythroid cells, we describe 
distinct GATA-1 interactions with the essential hematopoietic factor Gfi-1b, the 
repressive MeCP1 complex and the chromatin remodeling ACF/WCRF complex, in 
addition to the known GATA-1/FOG-1 and GATA-1/TAL-1 complexes. Importantly, we 
show that FOG-1 mediates GATA-1 interactions with the MeCP1 complex, thus 
providing an explanation for the overlapping functions of these two factors in 
erythropoiesis. We also show that subsets of GATA-1 gene targets are bound in 
vivo by distinct complexes, thus linking specific GATA-1 partners to distinct 
aspects of its functions. Based on these findings, we suggest a model for the 
different roles of GATA-1 in erythroid differentiation.