Negative modulation of ?1(I) procollagen gene expression in human skin fibroblasts: Transcriptional inhibition by interferon-?

Abstract

Interferon-gamma (IFN-gamma), a multifunctional cytokine produced by activated Th1 lymphocytes, exerts potent effects on the extracellular matrix by regulating fibroblast function. In this study, we examined the modulation of alpha1(I) procollagen gene (COL1A1) expression by recombinant IFN-gamma. The results showed that IFN-gamma stimulated the rapid accumulation of interferon regulated factor (IRF)-1 mRNA, followed by a delayed and dose-dependent inhibition of alpha1(I) procollagen mRNA expression in skin fibroblasts from several different donors. The inhibitory response was abrogated in fibroblasts stably expressing IRF-1 in the antisense orientation. A marked decrease in the amount of heterogeneous nuclear pre-mRNA preceded the inhibition of COL1A1 mRNA expression. In fibroblasts transiently transfected with COL1A1 promoter-chloramphenicol acetyltransferase reporter gene plasmids, IFN-gamma selectively inhibited promoter activity and abrogated its stimulation induced by TGF-beta. The inhibition by IFN-gamma was not due to downregulation of TGF-beta receptor mRNA expression in the fibroblasts or decreased ligand binding to the receptor. IFN-alpha and IFN-beta by themselves had little effect on promoter activity, but IFN-alpha augmented the inhibitory effect of IFN-gamma. Using a series of 5' deletion constructs, a proximal region of the COL1A1 promoter was shown to function as an IFN-gamma response element. This region of the gene harbors overlapping binding sites for transcription factors Sp1, Sp3, and NF-1 but no homologs of previously characterized IFN-gamma response elements. The putative IFN-gamma response region was sufficient to confer inhibition of reporter gene expression by treatment with IFN-gamma. Gel mobility shift analysis showed that two distinct and specific DNA-protein complexes were formed when fibroblast nuclear extracts were incubated with oligonucleotides spanning the IFN-gamma response region. IFN-gamma did not modify the ability of nuclear proteins to bind to this region. The results indicate that IFN-gamma inhibits COL1A1 expression in fibroblasts principally at the level of gene transcription. Inhibition involves IRF-1 and is mediated through a short proximal promoter segment but without an apparent change in promoter occupancy. The findings provide novel insight into the mechanism of IFN-gamma regulation of fibroblast function.

Collagen α1(I) Gene (COL1A1) Is Repressed by RFX Family

“…4C) similar to the ␣2(I) promoter (8). Because these proteins are induced during IFN-␥ treatment (15), we have confirmed results by others (27) that IFN-␥ represses ␣1(I) promoter activity as well as the endogenous COL1A1 steady state mRNA levels (Fig. 4D).…”

TNF-α and IFN-γ inversely modulate expression of the IL-17E receptor in airway smooth muscle cells

“…In contrast, IFN-␥, a known inhibitor of collagen-␣I synthesis, led to a 40 -50% decrease in procollagen-␣I mRNA (data not shown). Similar values were found in the literature regarding collagen-␣I mRNA modulation by TGF-␤ 1 and IFN-␥ in fibroblasts and hepatic stellate cells (3,36,78). This initial finding implies that IL-17E could participate with other Th2 and profibrotic cytokines and contribute to airway remodelling observed in asthmatics.…”

A 36-Amino-Acid Region of CIITA Is an Effective Inhibitor of CBP: Novel Mechanism of Gamma Interferon-Mediated Suppression of Collagen α2(I) and Other Promoters

“…The collagen promoter which was used as the prototype promoter to study CIITA-mediated gene repression turns out to be a primary target of IFN-␥-mediated gene repression (26,27,64). This led to our hypothesis that CIITA may be a mediator of the welldocumented gene repression by IFN-␥.…”