Expression of delta-aminolevulinate synthase durin erythroid differentiation

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Mouse erythroleukemia (MEL) cells undergo erythroid differentiation after treatment of dimethylsulfoxide (DMSO).Recently, we established DR cell, a clone of MEL cell, which could not undergo erythroid differentiation after DMSO treatment. Analysis revealed a deficiency of erythroid-specific delta-aminolevulinate synthase (ALAS-E) in DR cells. In addition, gene activation of delta-aminolevulinate dehydratase, porphobilonogen deaminase, and uroporphyrinogen decarboxylase-after DMSO treatment were reduced to approx. 1/3 of those in wild type cells.In the present study we evidenced that deficiency of heme in DR cells resulted in reduced concentrations of minas encoding ferrochelatase and beta-globin. Further studies suggest that insufficient supply of heme inhibits the gene activation of NF-E2. It is, therefore, suggested that NF-E2 might regulate heme biosynthesis in erythroid cells in a positive feedbach manner.Then, we have developed MEL cell lines, whose ALAS-E levels were declined by antisense RNA of the enzyme. Antisense RNA expression caused reductions not only in ALAS-E expression but also in the other heme pathway enzymes. These observations are in good agreement with those observed in DR cells. Furthermore, expression of ALAS-E antisense RNA also reduced NF-E2 mRNA.Thus, it is highly probable that NF-E2 plays one of the significant roles on positive feedback regulation of heme in erythroid cells.