Expression of tal-1 and GATA-binding proteins during human hematopoiesis

Tal-1 rearrangements are associated with nearly 30 % of human T acute lymphoblastic leukemia. Tal-1 gene encodes a putative transcription factor with a basic helix-loop-helix domain and is known to be predominantly expressed in he-matopoietic cells. We investigated the pattern of tal-1 expression in purified human hematopoietic cells by in situ hybridization and reverse transcriptase polymerase chain reaction analysis. Both methods demonstrated that the tal-l gene is expressed in megakaryocytes and erythroblasts as well as in basophilic granulocytes. In addition, our results indicate that the tal-1 1A promoter, which contains two consensus GATA-binding sites, is active mainly in these lineages. Because the GATA-1 gene is known to transac-tivate several genes specific for the erythroid, megakaryo-cytic, and mastocytic/basophilic lineages, we studie