Multiple epsilon-promoter elements participate in the developmental control of epsilon-globin genes in transgenic...

To delineate the regulation of the human epsilon-globin gene, we investigated epsilon-gene expression during the development of transgenic mice carrying constructs with epsilon-promoter truncations linked to a micro-locus control region (microLCR). Expression levels were compared with those of microLCR epsilon mice carrying a 2 kilobase epsilon-promoter and betaYAC controls. epsilon mRNA in the embryonic cells of microLCR (-179)epsilon mice were as high as in microLCR epsilon mice suggesting that the proximal epsilon-promoter contains most elements required for epsilon-gene activation. epsilon mRNA in adult microLCR (-179) epsilon mice was significantly lower than in the embryonic cells indicating that elements involved in epsilon-gene silencing are contained in the proximal epsilon-promoter. Extension of the promoter sequence to -463 epsilon decreased epsilon-gene expression in the definitive erythroid cells, supporting previous evidence that the -179 to -463epsilon region contains an epsilon-gene silencer. However, the epsilon-gene of the microLCR(-463)epsilon mice was not silenced in the definitive cells of fetal and adult erythropoiesis indicating that additional silencing elements are located upstream of position -463epsilon. These results provide in vivo evidence that multiple elements of the distal as well as the proximal promoter contribute to epsilon-gene silencing.