The ING4 Tumor Suppressor Attenuates NF-κB Activity at the Promoters of Target Genes

Abstract

The NF-κB family mediates immune and inflammatory responses. In many cancers, NF-κB is constitutively activated and induces the expression of genes that facilitate tumorigenesis. ING4 is a tumor suppressor that is absent or mutated in several cancers. Herein, we demonstrate that in human gliomas, NF-κB is constitutively activated, ING4 expression is negligible, and NF-κB-regulated gene expression is elevated. We demonstrate that an ING4 and NF-κB interaction exists but does not prevent NF-κB activation, nuclear translocation, or DNA binding. Instead, ING4 and NF-κB bind simultaneously at NF-κB-regulated promoters, and this binding correlates with reductions in p65 phosphorylation, p300, and the levels of acetylated histones and H3-Me3K4, while enhancing the levels of HDAC-1 at these promoters. Using a knockdown approach, we correlate reductions in ING4 protein levels with increased basal and inducible NF-κB target gene expression. Collectively, these data suggest that ING4 may specifically regulate the activity of NF-κB molecules that are bound to target gene promoters.

SUPPLEMENTAL MATERIAL

Supplemental material for this article may be found at http://mcb.asm.org/ .

ACKNOWLEDGMENTS

This work was supported in part by public service grants CA-97247 from the National Cancer Institute (E.N.B. and L.B.N.), NS-54158 from the National Institute of Neurological Disorders and Stroke (E.N.B., S.N., and L.B.N.), IRG-60-001-47 from the American Cancer Society, and CA-13148-31 from the National Cancer Institute (S.N.). The UAB NMDC facility is supported by public service grant P30 NS47466. The CFAR/CCC DNA Sequencing Core is supported by NIH CFAR core grant P30AI27767.

We thank the UAB Neuroscience Molecular Detection Core Facility (NMDC) staff for their assistance with immunohistochemistry experiments. We also thank Cheryl Palmer (University of Alabama at Birmingham) for providing human brain tissue resections, G. Yancey Gillespie and the UAB Brain Tumor Tissue core for providing the glioma and control samples used herein, and Courtney J. Haycraft and Shaun Sparacio for technical assistance. Finally, we recognize the efforts of Maria G. Salazar of the CFAR/CCC DNA Sequencing Core at UAB for expert advice and technical assistance.