Cooperation between SMAD and NF-κB in growth factor regulated type VII collagen gene expression

We have previously demonstrated that transforming growth factor-beta (TGF-beta) and pro-inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha) or interteukin-1 beta, synergistically enhance the expression of type VII collagen gene (COL7A1) in human dermal fibroblasts in culture (Mauviel rt nl., 1994), Recently, we identified a SMAD-containing complex, rapidly induced by TGF-beta and binding the region [-496/-444] of the COL7A1 promoter, responsible for COL7A1 gene transactivation (Vindevoghel rt al., 1998a), In this report, we demonstrate that TGF-beta and TNF-alpha response elements are distinct entities within the COL7A1 promoter. In particular, we demonstrate that the TNF-alpha effect is mediated by NF-kappa B1/RelA (p50/p65) and RelA/RelA (p65/p65) NF-kappa B complexes binding the TNF-alpha response element (TaRE) located in the region [-252/-230], with RelA acting as the transcriptional activator, Finally, we provide definitive evidence for the role of both TGF-beta and TNF-alpha response elements as enhancer sequences, functioning in the contest of a heterologous promoter in an additive manner in response to TGF-beta and TNF-alpha, This study provides the first identification of a functional interaction between the two immediate-early transcription factors, SMAD and NF-kappa B, to activate the expression of an extracellular matrix-related gene, COL7Al.