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BRCA1 regulates the interferon gamma-mediated apoptotic response
Heather N Andrews1, Paul B Mullan, Stewart McWilliams
1Department of Oncology, Cancer Research Centre, The Queen's University Belfast, Belfast BT9 7AB, Northern Ireland.
Abstract:
BRCA1 is a tumor suppressor gene implicated in transcriptional regulation. We have generated cell lines with inducible expression of BRCA1 as a tool to identify downstream targets that may be important mediators of BRCA1 function. Oligonucleotide array-based expression profiling identified 11 previously described interferon regulated genes that were up-regulated following inducible expression of BRCA1. Northern blot analysis revealed that a subset of the identified targets including IRF-7, MxA, and ISG-54 were synergistically up-regulated by BRCA1 in the presence of interferon gamma (IFN-gamma) but not interferons alpha or beta. Importantly, IFN-gamma-mediated induction of IRF-7 and MxA was attenuated in the BRCA1 mutant cell line HCC1937, an effect that was rescued following reconstitution of exogenous wild type BRCA1 in these cells. Furthermore, reconstituted BRCA1 sensitized HCC1937 cells to IFN-gamma-induced apoptotic cell death. This study identifies BRCA1 as a component of the IFN-gamma-regulated signaling pathway and suggests that BRCA1 may play a role in the regulation of IFN-gamma-mediated apoptosis.
Insights
This study reveals that BRCA1 (Breast Cancer gene 1) regulates interferon gamma signaling. BRCA1 influences interferon gamma-induced apoptosis, highlighting its role in immune response pathways.
Area of Science:
- Molecular Biology
- Cancer Genetics
- Immunology
Background:
- BRCA1 is a critical tumor suppressor gene involved in transcriptional regulation.
- Understanding BRCA1's downstream targets is key to elucidating its function in cancer suppression.
- Interferon signaling pathways play a significant role in cellular defense and tumor suppression.
Purpose of the Study:
- To identify downstream targets of BRCA1 using inducible expression systems.
- To investigate the interplay between BRCA1 and interferon signaling pathways.
- To explore BRCA1's role in interferon gamma-mediated apoptosis.
Main Methods:
- Generation of cell lines with inducible BRCA1 expression.
- Oligonucleotide array-based gene expression profiling to identify differentially expressed genes.
- Northern blot analysis to validate target gene regulation.
- Functional studies in BRCA1-mutant cell lines (HCC1937) with and without BRCA1 reconstitution.
Main Results:
- Inducible BRCA1 expression up-regulated 11 interferon-regulated genes.
- BRCA1 synergistically enhanced interferon gamma-induced expression of IRF-7, MxA, and ISG-54.
- Interferon gamma-mediated induction of IRF-7 and MxA was impaired in BRCA1-mutant cells and restored upon BRCA1 reintroduction.
- Reconstitution of BRCA1 sensitized cells to interferon gamma-induced apoptosis.
Conclusions:
- BRCA1 is identified as a component of the interferon gamma signaling pathway.
- BRCA1 plays a regulatory role in interferon gamma-mediated apoptosis.
- These findings suggest a novel mechanism by which BRCA1 contributes to tumor suppression and immune regulation.