BASAL EXPRESSION OF THE HUMAN MACROPHAGE-COLONY-STIMULATING FACTOR (M-CSF) GENE IN K562 CELLS

Macrophage colony-stimulating factor (M-CSF) functions in hematopoiesi s and regulates mature monocytes. Untreated K562 leukemic cells transc ribe M-CSF. Elements between bases -43 and -77 (NF-KB enhancer) and be tween -129 and -180 (Spl enhancer) of the M-CSF promoter were importan t for basal transcription. Gel Shift assays and ultraviolet crosslinki ng experiments showed a 50 kDa protein bound to the NF-KB element at - 65 in a GTP-dependent fashion. Additionally, a K562 nuclear protein, s pecifically bound the Sp1 enhancer. Run-off transcription and half-lif e studies showed that M-CSF is regulated primarily at the post-transcr iptional level.