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

Mol Endocrinol. 2002 Dec;16(12):2802-18. doi: 10.1210/me.2001-0292.

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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Binding Sites
  • Cell Nucleus / metabolism
  • Chromogranin A
  • Chromogranins / genetics*
  • Cyclic AMP Response Element-Binding Protein / metabolism*
  • DNA / chemistry
  • DNA / metabolism
  • DNA-Binding Proteins / metabolism*
  • Early Growth Response Protein 1
  • Enzyme Inhibitors / pharmacology
  • Epithelial Cells / metabolism
  • Flavonoids / pharmacology
  • Gastrins / pharmacology*
  • Humans
  • Immediate-Early Proteins*
  • Immunoblotting
  • MAP Kinase Kinase 1
  • Mitogen-Activated Protein Kinase 1 / metabolism
  • Mitogen-Activated Protein Kinase 3
  • Mitogen-Activated Protein Kinase Kinases / antagonists & inhibitors
  • Mitogen-Activated Protein Kinase Kinases / metabolism
  • Mitogen-Activated Protein Kinases / metabolism
  • Phosphorylation
  • Promoter Regions, Genetic
  • Protein-Serine-Threonine Kinases / antagonists & inhibitors
  • Protein-Serine-Threonine Kinases / metabolism
  • Response Elements
  • Signal Transduction
  • Stomach Neoplasms
  • Tetradecanoylphorbol Acetate / pharmacology
  • Transcription Factors / metabolism*
  • Transcriptional Activation
  • Transfection
  • Tumor Cells, Cultured

Substances

  • CHGA protein, human
  • Chromogranin A
  • Chromogranins
  • Cyclic AMP Response Element-Binding Protein
  • DNA-Binding Proteins
  • EGR1 protein, human
  • Early Growth Response Protein 1
  • Enzyme Inhibitors
  • Flavonoids
  • Gastrins
  • Immediate-Early Proteins
  • Transcription Factors
  • DNA
  • Protein-Serine-Threonine Kinases
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • Mitogen-Activated Protein Kinases
  • MAP Kinase Kinase 1
  • MAP2K1 protein, human
  • Mitogen-Activated Protein Kinase Kinases
  • Tetradecanoylphorbol Acetate
  • 2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one