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

The developmental stage-specific silencing of the human epsilon-globin gene during embryonic life is controlled, in part, by the silencer (-392 bp approximately -177 bp) 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 DNaseI footprinting assay, a major protected region from -278 bp to -235 bp 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 approximately 32, 28, 26 and 22 kD) 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 epsilon-globin gene expression at the fetal stage through the interactions with this silencer.