Constitutive silencing of IFN-beta promoter is mediated by NRF (NF-kappaB-repressing factor), a nuclear inhibitor of NF-kappaB.
Transcriptional regulation of the interferon-beta (IFN-beta) gene is characterized by strict constitutive repression and virus-specific activation. Previous studies have shown that the IFN-beta promoter is constitutively repressed by a negative regulatory element (NRE). Isolated NRE acts as a constitutive and position-independent silencer on the NF-kappaB-binding sites. Here, we describe the identification and functional characterization of the NRE-binding protein, called NRF (NF-kappaB-repressing factor), which abolishes the transcriptional activity of the bordering NF-kappaB- binding sites by a distance-independent mechanism. Deletion studies show that a minimal repression domain of NRF is sufficient to exert its inhibitory effect. In vitro, NF-kappaB proteins bind to purified NRF by a direct protein-protein interaction. We demonstrate that NRF is a ubiquitous and constitutive nuclear protein. In fibroblasts, the expression of the NRF antisense RNA releases the endogenous IFN-beta gene transcription. Our data strongly suggest that the NRF-mediated inhibition of NF-kappaB is a critical component of the IFN-beta gene silencing prior to viral infection.
Nourbakhsh
M
M
Department of Gene Regulation and Differentiation, GBF-National Research Institute for Biotechnology, Mascheroder Weg 1, D-38124 Braunschweig, Germany.
Hauser
H
H
D000595:Amino Acid Sequence; D001483:Base Sequence; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D016899:Interferon-beta / Q000096:biosynthesis / Q000235:genetics*; D008297:Male; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000037:antagonists & inhibitors*; D009928:Organ Specificity; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis; D012097:Repressor Proteins / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D014162:Transfection
D004268:DNA-Binding Proteins; D016328:NF-kappa B; C111027:NKRF protein, human; D012333:RNA, Messenger; D011994:Recombinant Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; D016899:Interferon-beta