Transcriptional regulation of a hematopoietic proteoglycan core protein gene during hematopoiesis

The expression of a hematopoietic proteoglycan core protein (HpPG) gene is up-regulated during the early stages of myeloblast differentiation at a time point coinciding with the beginning of granule genesis (Stellrecht, C. M., Mars, W. M., Miwa, H., Beran, M., and Saunders, G. F. (1991) Differentiation 48, 127-135). The mechanism of this up-regulatory event was investigated by analyzing the expression and regulation of the HpPG gene during the differentiation of the pluripotent hematopoietic cell line, K562. The level of HpPG gene expression in these cells was up-regulated approximately 10-fold upon 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced megakaryocytic differentiation, as measured by Northern blot analysis. The HpPG gene's expression remained relatively unchanged during hemin-induced erythroid differentiation, further demonstrating the specificity of this regulatory event for granule-producing cell lineages. The effect of TPA induction on HpPG gene expression was also assessed during the differentiation of the myeloid leukemia cell line, HL-60. The expression of the gene was down-regulated approximately 20-fold upon TPA-induced differentiation into macrophage-like cells. In contrast, only a minimal decrease in HpPG gene expression was detected in gamma-interferon-induced monocyte differentiation. No detectable changes in expression levels were seen in HL-60 cells differentiated into granulocytes with retinoic acid or dimethyl sulfoxide. Nuclear runoff analysis demonstrated that the regulation of the HpPG gene is under transcriptional control in both TPA-induced differentiation systems.