Basal expression of the human macrophage colony-stimulating factor (M-CSF) gene in K562 cells

Macrophage colony-stimulating factor (M-CSF) functions in hematopoiesis and regulates mature monocytes. Untreated K562 leukemic cells transcribe M-CSF. Elements between bases -43 and -77 (NF-KB enhancer) and between -129 and -180 (Sp1 enhancer) of the M-CSF promoter were important for basal transcription. Gel Shift assays and ultraviolet crosslinking experiments showed a 50 kDa protein bound to the NF-KB element at -65 in a GTP-dependent fashion. Additionally, a K562 nuclear protein, specifically bound the Sp1 enhancer. Run-off transcription and half-life studies showed that M-CSF is regulated primarily at the post-transcriptional level.