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Nuclear factor-kappaB and cAMP response element binding protein mediate opposite transcriptional effects on the
1Laboratorio di Patologia Vascolare, Istituto Dermopatico dell'Immacolata, Rome, Italy.
Abstract:
-The vascular endothelial growth factor receptor Flk-1/KDR is highly expressed during development and almost disappears in adult tissues. Despite its biological relevance, little is known about the molecular mechanisms controlling its expression. In the present work, it is shown that cAMP response element binding protein (CREB) and nuclear factor-kappaB (NF-kappaB)-related antigens bind specific sequences in the Flk-1/KDR promoter. Functional studies demonstrate that cAMP represses whereas tumor necrosis factor-alpha, an activator of NF-kappaB, stimulates promoter activity. Histone acetyltransferases (HATs) P/CAF and CBP/p300 together with p65/RelA, the catalytic subunit of NF-kappaB, increase Flk-1/KDR promoter activity 10- to 20-fold. Consistently, inhibition by cAMP is reverted by increasing intracellular HATs and is completely abolished by site-specific mutagenesis of the cAMP response element. In contrast, specific mutations in the NF-kappaB response element abolish responsiveness to p65/RelA and HATs without affecting cAMP-dependent repression. These results suggest that opposing signaling pathways, activating NF-kappaB or CREB and requiring HAT molecules, control Flk-1/KDR promoter activity.
Insights
Cyclic AMP response element-binding protein (CREB) and nuclear factor-kappaB (NF-kappaB) signaling pathways, along with histone acetyltransferases, regulate the Flk-1/KDR gene promoter. These opposing pathways control Flk-1/KDR expression, crucial for development.
Area of Science:
- Molecular Biology
- Gene Regulation
- Cell Signaling
Background:
- Vascular endothelial growth factor receptor (Flk-1/KDR) is vital during development but scarce in adults.
- Molecular mechanisms governing Flk-1/KDR expression remain largely uncharacterized.
Purpose of the Study:
- To elucidate the molecular mechanisms controlling Flk-1/KDR gene promoter activity.
- To investigate the roles of cAMP response element binding protein (CREB) and nuclear factor-kappaB (NF-kappaB) in regulating Flk-1/KDR expression.
Main Methods:
- Analysis of transcription factor binding to the Flk-1/KDR promoter.
- Functional studies using promoter activity assays with cAMP and tumor necrosis factor-alpha.
- Investigation of histone acetyltransferases (HATs) and specific promoter elements (cAMP response element, NF-kappaB response element).
Main Results:
- CREB and NF-kappaB-related factors bind to the Flk-1/KDR promoter.
- cAMP represses promoter activity, while tumor necrosis factor-alpha stimulates it.
- HATs (P/CAF, CBP/p300) and p65/RelA significantly increase promoter activity; cAMP inhibition is reversed by HATs and abolished by CREB element mutation, while NF-kappaB element mutations abolish NF-kappaB and HAT responsiveness.
Conclusions:
- Opposing signaling pathways involving NF-kappaB and CREB, dependent on HATs, modulate Flk-1/KDR promoter activity.
- These findings provide insight into the complex regulation of Flk-1/KDR during development and potentially in adult tissues.