A protein factor binding to an octamer motif in the gamma-globin promoter disappears upon induction of differentiation and hemoglobin synthesis in K562 cells.

Using the electrophoretic mobility shift assay and the footprinting technique, we studied the binding of nuclear proteins from erythroid and non erythroid human cells to the promoter region of the human gamma-globin gene. Two regions (A and B) of the promoter are bound by proteins present in uninduced K562 cells, but not in induced K562 cells nor in fetal liver erythroblasts; a protein binding to region A is also present in a variety of lymphoid and myeloid cells. Region B is centered on an octamer sequence identical to that present in immunoglobulin promoter and enhancers and other eukaryotic promoters; a B region binding protein common to K562 and other cells efficiently binds the octamer containing region of the histone H2B gene, while different B region proteins are more specific for uninduced K562 cells and the gamma-globin octamer containing fragment. The possible role of these nuclear proteins in gamma-globin gene regulation and/or cell differentiation is discussed.