Interaction of cytokine- and glucocorticoid-response elements of acute-phase plasma protein genes. Importance of glucocorticoid receptor level and cell type for regulation of the elements from rat alpha 1-acid glycoprotein and beta-fibrinogen genes

Abstract

Dexamethasone increased the transscriptional activity of several acute-phase plasma protein genes in cytokine-treated HepG2 cells, suggesting the presence of functional glucocorticoid receptors (GR). The level of GR was, however, insufficient for stimulation of transiently transfected gene constructs containing glucocorticoid-response elements (GRE). By complementation of HepG2 cells with a GR expression vector, a cell system was generated that allowed analysis of the interaction between GRE and cytokine-response elements of the rat alpha 1-acid glycoprotein gene and identification of the principal regulatory elements of the rat beta-fibrinogen gene. Although the expression of plasmid-derived GR mRNA was reduced by dexamethasone treatment, the concentration of GR was sufficient for full, short-term stimulation of GRE-containing vectors. By comparing the pattern of regulation of the cloned GRES in HepG2 and mouse L-cells, an equivalent, cell-type independent dexamethasone response was monitored for the alpha 1-acid glycoprotein element but a response limited to HepG2 cells was found for the beta-fibrinogen element. The data indicate that, although substantial differences exist in the organization and composition of the regulatory elements of the two genes, the overall function is, nevertheless, remarkably similar.