Negative regulation of monocyte chemoattractant protein-1 gene expression by a mouse estrogen-enhanced transcript.

A novel gene containing two typical estrogen responsive elements (ERE) was cloned from MTEC1 cells, a mouse thymus epithelial cell line that produces constitutively many chemokines. This gene is a homologue of the rat estrogen-enhanced transcript (EET) gene, and is called the mEET gene. mEET protein is expressed in cytoplasm. Addition of 17 beta-estradiol (E2) to the MTEC1 cell cultures enhanced mEET mRNA expression and, meanwhile, significantly inhibited monocyte chemoattractant protein-1 (MCP-1) production. To analyze the functional links between the expression of mEET and of MCP-1, we transfected MTEC1 cells with ERE-deleted antisense- or sense-mEET complementary (c)DNA construct and activated the transfected mEET cDNA in stable MTEC1 transfectants with doxycycline (Dox). Dox-induced activation of the mEET gene profoundly inhibited MCP-1 expression at both mRNA and protein levels and alleviated its chemotactic activity. Conversely, inactivation of the mEET gene substantially augmented MCP-1 expression. Activation of the mEET gene markedly attenuated activity of nuclear NF-kappaB. In summary, we have first demonstrated that estrogen-imposed inhibition of MCP-1 expression occurs through the activation of the mEET gene, its product suppresses nuclear NF-kappaB and negatively regulates MCP-1 gene activation.