Targets of the Tal1 transcription factor in erythrocytes: E2 ubiquitin conjugase regulation by Tal1

The Tal1 transcription factor is essential for the development of the hematopoietic system and plays a role during definitive erythropoiesis in the adult. Despite the importance of Tal1 in erythropoiesis only a small number of erythroid differentiation target genes are known. A chromatin precipitation and cloning approach was established to uncover novel Tal1 target genes in erythropoiesis. The BirA-tag/BirA-ligase biotinylation system in combination with streptavidine chromatin precipitation (Strep-CP) was used to co-precipitate genomic DNA bound to Tal1. Tal1 was found to bind in the vicinity of 31 genes including the E2-ubiquitin conjugase UBE2H gene. Binding of Tal1 to UBE2H was confirmed by chromatin immuno-precipitation. UBE2H expression is increased during erythroid differentiation of hCD34+ cells. Tal1 expression activated UBE2H expression whereas Tal1 knock-down reduced UBE2H expression and ubiquitin transfer activity. This study identifies parts of the ubiquitinylation machinery as a cellular target down-stream of the transcription factor Tal1 and provides novel insights into Tal1 regulated erythropoiesis.