Activation of the human β-globin promoter in K562 cells by DNA sequences 5' to the fetal γ- or embryonic ζ-globin genes

Abstract

Regulatory sequences of the human fetal γ-globin gene were studied by constructing composite γ/β globin promoters and comparing their function to that of intact β promoters in human K562 cells. The β-globin gene with either 1,600 or 127 basepairs of β promoter sequence was not expressed after stable introduction into K562 cells, consistent with the known inactivity of the β-globin gene in these cels. In contrast, a γ/β promoter composed of a γ fragment spanning positions -408 to -137 joined to the 127-bp β promoter was able to drive the β-globin gene. The gene appeared to be inducible with hemin. A ζ-globin 5' flanking fragment also activated the β promoter. The function of a series of composite γ/β promoters was then assessed by their ability to drive directly the neomycin resistance gene, again in stably transformed cells. The -408 to -137 γ fragment activated the β promoter in an orientation-specific manner in this assay. Deletion analysis showed that regulatory sequences were present between positions -259 and -137 of the fetal γ-globin gene flanking region.