Globin Gene Enhancer Activity of a DNase-I Hypersensitive Site-40 Homolog in Medaka, Oryzias latipes

In medaka, we found a C16orf35-like gene in the region within 1 Kbp 3' downstream of the psibeta end of the 36-Kbp embryonic globin gene cluster ((5')alpha0(3')-(3')beta1(5')-(5')alpha1(3')-(5')beta2(3')-(5')alpha2(3')-(3')alpha3(5')-(5')beta3(3')-(3')beta4(5')-(5')alpha4(3')-(3')psialpha(5')-(5')psibeta(3')). Intron 5 of the gene contained a region having NF-E2 binding sites located between GATA boxes. The region was homologous to human HS-40 in terms of the existence and structure of characteristic transcription-factor binding sites and was named Ol-HS-40. Injection of the fusion gene construct Ol-HS-40-alpha0(up-2)GFP, consisting of Ol-HS-40, a 5' upstream 200-bp minimum promoter for alpha0, and green fluorescent protein (GFP), showed that Ol-HS-40, as in human HS-40, had the ability to strongly enhance GFP expression in erythroid cells of embryos. Further analysis using transgenic technology revealed that Ol-HS-40 had the ability to change the type of the GFP expression from embryo-to-young fish to embryo-to-adult. In addition, the results suggest that Ol-HS-40, although its natural function remains unclear, has strong enhancer activity for the expression of not only the alpha-globin gene but also the beta-globin gene.