Interaction of Early Growth Response Protein 1 (Egr-1), Specificity Protein 1 (Sp1), and Cyclic Adenosine 3′5′-Monophosphate Response Element Binding Protein (CREB) at a Proximal Response Element Is Critical for Gastrin-Dependent Activation of the Chromogranin A Promoter

Abstract

Recently, binding of specific protein 1 (Sp1) and cAMP response element binding protein (CREB) to a GC-rich element at -92/-62 has been identified as a critical step in gastrin-dependent regulation of the chromogranin A (CgA) gene in gastric epithelial cells. Here we demonstrate that binding of early growth response protein 1 (Egr-1) to the distal part of the -92/-62 site is also required for gastrin-dependent CgA transactivation. Gastrin elevated cellular and nuclear Egr-1 levels in a time-dependent manner and also increased Egr-1 binding to the CgA -92/-73 region. Disruption of this site reduced gastrin responsiveness without influencing basal promoter activity, while loss of Sp1 and/or CREB binding sites diminished basal and gastrin-stimulated CgA promoter activity. Ectopic Egr-1 overexpression potently stimulated the CgA promoter, whereas coexpression of Egr-1 with Sp1 and/or CREB resulted in additive effects. Functional analysis of Sp1-, Egr-1-, or CREB-specific promoter mutations in transfection studies confirmed the tripartite organization of the CgA -92/-62 element. Signaling studies revealed that MAPK kinase 1 (MEK1)/ERK1/2 cascades are critical for gastrin-dependent Egr-1 protein accumulation as well as Egr-1 binding to the CgA promoter. Our studies for the first time identify Egr-1 as a nuclear target of gastrin and show that functional interplay of Egr-1, Sp1, and CREB is indispensable for gastrin-dependent CgA transactivation in gastric epithelial cells.

Essential Interaction of Egr-1 at an Islet-specific Response Element for Basal and Gastrin-dependent Glucagon Gene Transactivation in Pancreatic α-Cells

“…Furthermore, we show phosphorylation of Egr-1 after gastrin stimulation, consistent with the DNA binding activity of Egr-1 (19). Participation of Egr-1 in gastrin-regulated transactivation of promoter was reported for the chromogranin A gene in gastric epithelial cells (25). Similar to our results, gastrin-dependent binding of Egr-1 to chromogranin A promoter was rapid, transient, disappearing after a maximum at 1 h, and involved the MEK1/ERK1/2 signaling cascade.…”

A novel anticancer effect of Astragalus saponins: Transcriptional activation of NSAID‐activated gene

“…As a result, we propose that Egr-1 should be a major mediator in the AST-induced NAG-1 activation. Since Egr-1 can be phosphorylated by extracellularsignal-regulated kinase ERK, 42 it has been suggested to be activated through the ERK signaling pathway. 16 In the same study, investigators also discovered that troglitazone, a peroxisome proliferators-activated receptor a ligand, would induce ERK activity that seems to be critical in regulating Egr-1 expression.…”

Expression of NAG-1, a Transforming Growth Factor-β Superfamily Member, by Troglitazone Requires the Early Growth Response Gene EGR-1

“…5A, cotransfection of EGR-1 increased NAG-1 promoter activity after TGZ treatment, whereas Sp1 expression resulted in the reduction of NAG-1 promoter activity compared with empty vector transfection. Functional interplay between Sp1 and EGR-1 has been described for a number of human gene promoters (49,(52)(53)(54). The cis-acting element required for Sp1/EGR-1 binding is usually represented by a GC-rich sequence (GC box).…”

“…NAG-1 expression was also increased by TGZ treatment, with the increase in EGR-1 expression by TGZ always preceding that in NAG-1 expression. EGR-1 can be phosphorylated by ERK kinases, but the importance of the phosphorylation in the biological function of EGR-1 is not understood (49). TGZ induces ERK1/2 phosphorylation and activity in these cells, which appear to regulate the expression of EGR-1 by post-transcriptional and posttranslational mechanisms (25).…”