Stimulus-Specific Assembly of Enhancer Complexes on the Tumor Necrosis Factor Alpha Gene Promoter

Abstract

The human tumor necrosis factor alpha (TNF-α) gene is rapidly activated in response to multiple signals of stress and inflammation. We have identified transcription factors present in the TNF-α enhancer complex in vivo following ionophore stimulation (ATF-2/Jun and NFAT) and virus infection (ATF-2/Jun, NFAT, and Sp1), demonstrating a novel role for NFAT and Sp1 in virus induction of gene expression. We show that virus infection results in calcium flux and calcineurin-dependent NFAT dephosphorylation; however, relatively lower levels of NFAT are present in the nucleus following virus infection as compared to ionophore stimulation. Strikingly, Sp1 functionally synergizes with NFAT and ATF-2/c-jun in the activation of TNF-α gene transcription and selectively associates with the TNF-α promoter upon virus infection but not upon ionophore stimulation in vivo. We conclude that the specificity of TNF-α transcriptional activation is achieved through the assembly of stimulus-specific enhancer complexes and through synergistic interactions among the distinct activators within these enhancer complexes.

ACKNOWLEDGMENTS

We are indebted to Tim Hoey for the generous gift of an unpublished NFATp antibody. We are grateful to Lori Daniels for laboratory assistance, Ann Corbett for help with manuscript preparation, and Judith Grisham for editorial assistance. We also thank Anjana Rao and Jeremiah Hagler for gifts of reagents.

This work was supported by an Established Investigator Award from the American Heart Association to A.E.G. and by grants from the National Institutes of Health to D.T. (GM54605) and T.M. (AI20642).

J.V.F. and A.M.U. contributed equally to this work.