The Regulation Of NF-E2 On Erythroid Hematopoiesis

NF-E2 (nuclear factor erythroid 2) is a basic leucine zipper protein which is belong to CNC transcriptional family. NF-E2 is critical for the globin expression. The binding of NF-E2 to the MARES in the DNase I hypersensitivity site HS2 which is located in the LCR (locus control region) of P globin induce the high expression of 3 globin. There is also NF-E2 binding site in the HS40 site which is the enhancer of a globin. NF-E2 is a heterozimer which is formed by 2 subunit p18 and p45. p28 is a widely expressed protein. p45 subunit is tissue restricted protein which is almost exclusively found only in hematopoeitic processor, erythroid cell, megakyrocyte, granule cell. In addition to the function on the erythroid differentiation, it is also essential for normal platelet production. Targeted disruption of the gene encoding the 45 kDa subunit leads to severe thrombocytopenia but little if any defect in erythropoiesis, indicating that other molecules can compensate p45 's function in red cell maturation in vivo.However, retroviral integration within the p45 gene has been shown to disrupt erythroid di€erentiation in erythroleukemia cells. In the erythroid cell line CBS, due to the intergration of previrus, one allele p45NF-E2 is inactive and another allele is lost during the development. Indicate the antitumor effect of NF-E2 in the development of the erythroid leukemia induced by the friend virus . Injected the friend virus to p45NF-E2+ new born mice to induce erythroidleukemia, the p45NF-E2+ mice succumb to the disease moderately but significantly faster than +/+ mice. In addition, the spleens of +/- mice were significantly larger than those of +/+ mice. Only the tumors generated from +/-mice gave rise to cell lines, establishment in culture was associated with the loss of the remaining wild-type p45 NFE2 allele in most of the cell lines. Indicate that p45 NFE2 functions as an inhibitor of erythroid cell growth and that perturbation of its expression contributes to the progression of Friend erythroleukemia.In order to clarify the mechanism of the antitumor function of NF-E2 we transfected the p45NF-E2 to CB3 and HB22.2 cell in which the p45NF-E2 is null due to the previrus intergration. Globin expression was recruited after the transfection. The cell growth was much slower in HB22.2 cell transfected with p45NF-E2 compare to the control cell. The Cyclin dependent kinase(CDK) inhibitor p27 was upregulated significantly. But in CB3 cell line there was no change between transfected cell and control cell, the resean maybe due to there is much more gene inactive in CB3 cell than in HB22.2 cell. In HB60-5 cell which was induced erythroid differentiation after the withdraw of SCF in the culter medium. The p45NF-E2 and globin was upregulated gradually, simultaneously, p27 was also upregulated.p27 can slow down the cell cycle by inhibiting the activation of CDK, conversely, the activated CDK2 can phosphorylated the Threoninel87 of p27 which can be degradated by ubiquitin dependent proteasome. Cyclin Dl plays important role in the degradation of p27. Cyclin Dl is a switch in the cell cycle. While cell external mitosis stimulation cause increasing of Cyclin Dl, p27 assembly Cyclin Dl and CDK4 complexity. The Cyclin D1/CDK4 sequesters p27and blocks the interaction of p27 and Cyclin E1CDK2. More activated CDK2 causes more degradiation of p27.In HB22.2 cell the expression of p45NF-E2 leaded to deregulated of Cyclin Dl and CDK2, and the interaction of p27 and CDK2 was more obviously than that in control cells. In HB60-5 cell which was induced erythroid differentiation, the change of cell cycle relative protein is similarly. To demonstrated whether the antitumor effect is dependent on the erythroid differentiation, we transfected p45NF-E2 to COS1 cell which is monkey kidney cell lines. We also got p27 upregulation an Cyclin Dl down regulation, but there is no CDK2 decreasing and the enhanced p27/CDK2 interaction.To elucidate the genes expression regulated by NF-E2, we use microarray to screen the gene in mice fetus li...