Hypoxia-Inducible Factor 1-Mediated Human GATA1 Induction Promotes Erythroid Differentiation Under Hypoxic Conditions

Abstract 4794

The stimulation of red blood cell (RBC) production is one of the systemic adaptions to hypoxia. Hypoxia-inducible factor (HIF) promotes erythropoiesis through coordinated cell type-specific hypoxia responses. Hematopoietic transcription factor GATA1 is essential to normal erythropoiesis and plays a crucial role in erythroid differentiation. In this study, we show that hypoxia-induced GATA1 expression is mediated by HIF1 in erythroid cells. Under hypoxic conditions, significantly increased GATA1 mRNA and protein levels were detected in K562 cells and erythroid induction cultures of CD34⁺ hematopoietic stem/progenitor cells (HPCs) derived from human cord blood. Enforced HIF1Á expression increased GATA1 expression, while HIF1Á knock-down by RNA interference decreased GATA1 expression in K562 cells. We searched the human GATA1 gene sequence on NCBI and identified a putative HRE in the 3'-flanking sequence of the gene. The results from reporter gene and mutation analysis suggested that this element is necessary for hypoxic response. Chromatin immunoprecipitation (ChIP)-PCR showed that the putative HRE was recognized and bound by HIF1 in vivo. These results demonstrate that the up-regulation of GATA1 during hypoxia is directly mediated by HIF1.The mRNA expression of some erythroid differentiation markers was increased under hypoxic conditions, but decreased with RNA interference of HIF1Á or GATA1. Flow cytometry analysis also indicated that hypoxia or desferrioxamine or CoCl₂ induced expression of erythroid surface marker CD71 and CD235a, while expression repression of HIF1Á or GATA1 by RNA interference led to a decreased expression of CD235a. These results suggested that HIF1-mediated GATA1 upregulation promotes erythropoiesis in order to satisfy the needs of an organism under hypoxic conditions.