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NFkappaB activation is required for interferon regulatory factor-1-mediated interferon beta induction
S Kirchhoff1, D Wilhelm, P Angel
1Department of Gene Regulation and Differentiation, National Research Center for Biotechnology, Braunschweig, Germany.
European Journal of Biochemistry
|April 24, 1999
Summary
Interferon regulatory factor 1 (IRF-1) activates interferon beta (IFN-beta) gene expression by initiating NF-kappaB activation. This involves IRF-1-induced degradation of IkappaBalpha, allowing NF-kappaB to enhance IFN-beta transcription.
Area of Science:
- Immunology
- Molecular Biology
- Gene Regulation
Background:
- Interferon regulatory factor 1 (IRF-1) is a key transcriptional inducer of interferon beta (IFN-beta) and other interferon-stimulated genes.
- The precise mechanism of IRF-1-mediated IFN-beta induction, particularly its relationship with NF-kappaB signaling, requires further elucidation.
Purpose of the Study:
- To investigate the role of NF-kappaB activity in IRF-1-mediated IFN-beta gene induction.
- To identify the specific molecular events linking IRF-1 to NF-kappaB activation and subsequent IFN-beta transcription.
Main Methods:
- Analysis of NF-kappaB activation in cells expressing IRF-1.
- Investigation of the interaction between IRF-1 and NF-kappaB signaling components, including IkappaBalpha.
- Examination of cis-element binding and transcriptional activity on the IFN-beta promoter.
- In vitro phosphorylation assays using recombinant IkappaBalpha and cell extracts.
- Use of dominant-negative mutants of protein kinase PKR to assess its role in the pathway.
Main Results:
- IRF-1-mediated IFN-beta induction is dependent on NF-kappaB activity.
- IRF-1 directly initiates NF-kappaB activation by inducing the degradation of its inhibitor, IkappaBalpha.
- NF-kappaB, upon nuclear translocation, synergizes with IRF-1 on specific promoter regions (PRDII and PRDI/III) to drive IFN-beta transcription.
- Unlike dsRNA or virus-induced pathways, c-Jun/ATF-2 binding to PRDIV is not involved in IRF-1-mediated induction.
- Recombinant IkappaBalpha is phosphorylated by extracts from IRF-1-expressing cells.
- PKR (protein kinase R) appears to mediate IRF-1-dependent IkappaBalpha degradation.
Conclusions:
- IRF-1 orchestrates IFN-beta gene transcription through a pathway involving NF-kappaB activation and IkappaBalpha degradation.
- The findings reveal a novel mechanism of IRF-1 action, highlighting its role in initiating NF-kappaB signaling, potentially mediated by PKR.