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KMID : 0387720130240010021
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Korean Journal of Blood Transfusion
2013 Volume.24 No. 1 p.21 ~ p.32
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Functional Interaction of HIF-1 and NF-kB Increasing the Transcriptional Activation of TNF-a Gene in Monocytes
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Park Min-Jeong
Lee Sun-Min
Ok Soon-Jung
Kim Hye-Rim
Kim Hyung-Hoi
Cheong Jae-Hun
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Abstract
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Background:Tumor necrosis factor alpha (TNF-a) is a pleiotropic cytokine fulfilling a broad variety of immunoregulatory functions. Monocytes and macrophages play a pivotal role in inflammation and immune regulation. NF-kB and HIF-1 are known to increase expression of the TNF-a gene in a separate way.
Methods:Human monocytic leukemia, U937 cells, were transfected using the standard electroporation method for intracellular expression of NF-kB and HIF-1. We performed analysis using the mammalian two-hybrid assay and co-immunoprecipitation assay for detection of protein interaction of both proteins. In addition, chromatin immunoprecipitation analysis was performed for examination of NF-kB and HIF-1 binding on the TNF-a gene promoter.
Results:Here we show that NF-kB and HIF-1 cooperatively induced an increase in expression of the TNF-a gene dependent on promoter activity by the direct protein interaction of these two transcription factors. Hypoxia signaling induced marked enhancement of the transactivation of TNF-a promoter by HIF-1 and NF-kB. A tandem NF-kB/HIF-1 binding site was identified within the TNF-a promoter, which acted as a strong enhancer element. Physical association of the Rel domain of NF-kB and the N-TD domain of HIF-1 was required. Hypoxia treatment also resulted in a significant increase in the protein interaction of NF-kB and HIF-1 in vivo. Both transcription factors were recruited on the chromatin TNF-a promoter dependent on hypoxia stimuli.
Conclusion:The results of this study indicate that a variety of extracellular signals for activation of TNF-a gene expression might converge on the transcriptional regulation through the NF-kB/HIF-1 signaling pathway.
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KEYWORD
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HIF-1, NF-kB, Hypoxia, TNF-a, Transactivation
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