CELL-TYPE-SPECIFIC TRANSACTIVATION OF THE VCAM-1 PROMOTER THROUGH AN NF-KAPPA-B ENHANCER MOTIF

Cytokine activation of vascular cell adhesion molecule-1 (VCAM-1) gene expression by endothelial cells is an important feature in a variety of vascular inflammatory responses. Cytokines transcriptionally activa te the VCAM-1 promoter in endothelial cells at least in part through t wo closely linked NF-kappa B enhancer motifs, kappa L-kappa R (positio ns -77 and -63). However, cytokine activation of the dimeric NF-kappa B transcriptional factor (p50+p65 subunits) occurs in almost all cell types, whereas VCAM-1 gene expression exhibits a cell type-specific pa ttern of expression. Tumor necrosis factor-alpha markedly transactivat ed a transiently transfected minimal kappa L-kappa R motif-driven VCAM -1 promoter, p85VCAMCAT, in passaged human vascular endothelial cells but not in the human epithelial cell line, HeLa suggesting that cell t ype-specific factors may function through the kappa L-kappa R motif. B oth cell types exhibited similar inductions of NF-kappa B DNA binding activity and transcriptional activity. However, co-transfection of HeL a cells with p65 and p50 expression vectors demonstrated that the mini mal VCAM-1 promoter was effectively transactivated by p65 alone but th at additional co-expression of p50 blocked this activity. Furthermore, cytokine activation of the minimal VCAM-1 promoter in HeLa cells was recovered by inhibition of p50 expression using antisense oligonucleot ide. These studies suggest that the NF-kappa B(p50+p65 heterodimer) do es not support transactivation of the VCAM-1 promoter with the p50 sub unit potentially playing a significant inhibitory role in suppressing cytokine activation of VCAM-1. In addition, p65 associated transcripti onal factors other than NF-kappa B may serve as positive, cytokine-ind ucible, cell type specific regulators of VCAM-1 gene expression.