Activation of the Human jl - Globin Promoter in K 562 Cells by DNA Sequences 5 ' to the Fetal Ay - or Embryonic t - Globin Genes

Regulatory sequences of the human fetal -t-globin gene were studied by constructing composite 'y/ft globin promoters and comparing their function to that of intact , promoters in human K562 cells. The.8-globin gene with either 1,600 or 127 basepairs of 0 promoter sequence was not expressed after stable introduction into K562 cells, consistent with the known inactivity of the tBglobin gene in these cells. In contrast, a iy/, promoter composed of a y fragment spanning positions -408 to -137 joined to the 127-bp 0 promoter was able to drive the jt globin gene. The gene appeared to be inducible with hemin. A t-globin 5' flanking fragment also activated the f promoter. The function of a series of composite y/at promoters was then assessed by their ability to drive directly the neomycin resistance gene, ain in stably transformed cells. The -408 to -137 -y fragment activated the ft 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 y-globin gene flanking region.