Trans-acting factors from the human fetal liver binding to the human ε-globin gene silencer

The developmental stage-specific silencing of the human e-globin gene during embryonic life is controlled, in part, by the silencer (-392bp ∼ -177bp) upstream of this gene. In order to elucidate its role, the nuclear extract from the human fetal liver has been prepared and the interactions between trans-acting factors and this silencer element have been examined. By using DNasel footprinting assay, a major protected region from -278bp to -235bp within this silencer element was identified. Furthermore, we found in gel mobility shift assay and Southwestern blotting assay that there were at least four trans-acting factors (MW ≈ 32, 28, 26 and 22kD) in the nuclear extract isolated from the human fetal liver, which could specifically bind to this region. Our results suggested that these trans-acting factors might play an important role in silencing the human embryonic ε-globin gene expression at the fetal stage through the interactions with this silencer.