Mechanism of Differentiation of HEL Cells Induced by Hydroxyurea

HEL cells, a human erythroleukemia cell line, mainly express fetal globin gene(gamma) and small amount of the embryonic(epsilon) globin gene, but not the adult (beta) globin gene. Our previous studies demonstrated that hydroxyurea could induce HEL cells to express adult (beta) globin gene and induce HEL cells to terminal differentiation. In order to reveal the differentiation mechanism of HEL cells induced by hydroxyurea, GMSA was performed to examine the binding of nuclear extracts from hydroxyurea induced and uninduced HEL cells to the positive control region in the 5'-flanking sequence of human beta-globin gene and to the synthesized GATA oligonucleotides. Our results showed that, in the nuclear proteins from the induced HEL cells, the binding of GATA-1 to GATA motif was increased. However, the binding of GATA-2 to GATA motif was decreased. Besides, our data showed that a YY1-like protein was decreased quickly in hydroxyurea induced HEL cells. Western blotting analysis was used to analyze variation of GATA proteins in nuclei of HEL cells. Results revealed that the amount of GATA-2 was significantly decreased while the amount of GATA-1 was increased after HEL cells were induced for 12 h. These results indicate that GATA-1 may play a critical role in inducing HEL cells to terminal differentiation. The YY1-like protein and GATA-2 might inhibit HEL cells from terminal differentiation.