Advisory Committee Chair
Etty Benveniste
Advisory Committee Members
Xinbin Chen
Stuart Frank
Louis Nabors
Scott Wilson
Document Type
Dissertation
Date of Award
2008
Degree Name by School
Doctor of Philosophy (PhD) Heersink School of Medicine
Abstract
Interleukin-8 (IL-8) is a potent chemoattractant of numerous cells, particularly neutrophils, in the innate immune response. In addition to immune functions, IL-8 is known to contribute to the pathogenesis of a number of diseases, including cancer. Interferon-β (IFN-β), a Type I interferon, inhibits the expression of IL-8, but the details of this effect are not known. In this study we investigate transcriptional control of the IL- 8 gene and the mechanism by which IFN-β exerts inhibitory effects on IL-8. Herein we show that stimulation of U87-MG glioma cells with phorbol 12-myristate 13-acetate (PMA) results in a rapid recruitment of NF-κB p65 to the IL-8 promoter. Additionally, we show that the IL-8 promoter is constitutively acetylated on histones 3 and 4, indicating that the gene is accessible to transcription factors. Positive regulators of gene transcription such as the histone acetyltransferase (HAT) p300 are rapidly recruited to the IL-8 promoter along with RNA polymerase II. At the same time, negative regulators such as the histone deacetylases (HDACs) 1 and 3 that are constitutively present at the IL-8 promoter are dismissed. Upon treatment with IFN-β, however, there are rapid decreases in acetylation of histones 3 and 4 along with decreased levels of NF-κB p65 and RNA polymerase II present at the IL-8 promoter. We show that these promoter effects result in decreased IL-8 promoter activity, mRNA levels and protein levels when cells are treated with IFN-β. iv We also demonstrate that all three components of the Interferon Stimulated Gene Factor 3 (ISGF3) complex, namely the Signal Transducer and Activator of Transcription (STAT) proteins 1 and 2 and the accessory factor Interferon Regulatory Factor-9 (IRF-9), are required for IFN-β to mediate inhibitory effects on IL-8. In contrast to gene induction by this complex, however, STAT-1 and -2 transactivation domains were not required for inhibition by IFN-β. This work defines the promoter-specific events necessary for induction of IL-8 expression in malignant asctrocytoma cells, and the mechanistic requirements for inhibition of IL-8 by IFN-β in these cells.
Recommended Citation
Laver, Travis, "Mechanism Of Interferon-Beta-Mediated Inhibition Of Il-8 Gene Expression" (2008). All ETDs from UAB. 3741.
https://digitalcommons.library.uab.edu/etd-collection/3741