Transcriptional Regulation of Activating Transcription Factor 3 Involves the Early Growth Response-1 Gene

Abstract

Previously, our laboratory identified activating transcription factor 3 (ATF3) as up-regulated by nonsteroidal anti-inflammatory drugs using microarray analysis of mRNA from human colorectal cancer cells treated with sulindac sulfide. ATF3 is a transcription factor involved in cell growth, apoptosis, and invasion and is induced by a variety of anticancer and dietary compounds. However, the regulation of ATF3 by anticancer agents is not known. The promoter of ATF3 contains several transcription factor binding sites. We identified three putative Egr-1 binding sites in the promoter of ATF3 and report for the first time that the molecular mechanism responsible for the transcriptional regulation of ATF3 by two divergent pharmaceutical compounds, sulindac sulfide and troglitazone, involved the early growth response gene-1 (Egr-1). For example, overexpression of Egr-1 protein induced ATF3 mRNA 3.5-fold and transcriptional activity of an ATF3 promoter construct more than 20-fold. ATF3 and Egr-1 mRNA and protein and ATF3 promoter activity were induced by these compounds, whereas induction of ATF3 by these compounds was blocked by Egr-1 small interfering RNA. Sulindac sulfide and troglitazone regulated ATF3 promoter activity, which was suppressed when the two Egr-1 sites were mutated. These compounds induced phosphorylation of extracellular signal-regulated kinase1/2 (Erk1/2), whereas a dominant-negative inhibitor of mitogenactivate protein kinase kinase (MEK) 1 blocked the induction of ATF3. The MEK1/2 inhibitor PD98059 (2Ј-amino-3Ј-methoxyflavone) blocked the induction of ATF3 and Egr-1 mRNA expression and ATF3 promoter activity by these compounds. Therefore, this is a novel first report demonstrating that the expression of ATF3 occurs via Egr-1 downstream of Erk1/2.

Thapsigargin Induces Expression of Activating Transcription Factor 3 in Human Keratinocytes Involving Ca2+ Ions and c-Jun N-Terminal Protein Kinase

“…As a further proof, we showed that the selective activation of the ERK signaling pathway in HaCaT cells expressing a conditionally active form of A-Raf protein kinase induced expression of the zinc finger protein Egr-1 but not expression of ATF3. Egr-1 has been shown to transactivate the ATF3 gene in sulindac sulfideor troglitazone-treated human colorectal cancer cells or GnRHstimulated gonadotrophs (Bottone et al, 2005, Mayer et al, 2008a. The results presented here showed that Egr-1 plays no role in the thapsigargin-stimulated up-regulation of ATF3 in HaCaT keratinocytes.…”

ATF3-Dependent Regulation of EGR1 in vitro and in vivo

“…This molecule belongs to the ATF3/CREB transcription factor family [4], which is described as a tumour suppressor. Additionally, we detected an upregulation of EGR1, another transcription factor and immediate early gene belonging to the EGR family of C 2 H 2 -type zinc-finger proteins, which is discussed to be necessary for the induction of ATF3 [21]. …”

Early Epithelial Restitution by Nonsteroidal Anti-Inflammatory Drug–Activated Gene 1 Counteracts Intestinal Ulcerative Injuries

“…Intestinal epithelial injury activates these protective PKR-ERK1/2 signals, leading to induction of target genes, such as early growth response gene 1 involved in the regeneration process (49,50). NSAIDs enhance early growth response gene 1 expression via ERK1/2 signaling pathway, which attenuates NSAID-induced epithelial cytotoxicity (51,52). In the current study, NAG-1 also played protective roles against ulcerative injuries by promoting epithelial restitution.…”