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BRCA1 and GATA3 corepress FOXC1 to inhibit the pathogenesis of basal-like breast cancers
D Tkocz1, N T Crawford, N E Buckley
1Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, UK.
Abstract:
In this study we describe a novel interaction between the breast/ovarian tumor suppressor gene BRCA1 and the transcription factor GATA3, an interaction, which is important for normal breast differentiation. We show that the BRCA1-GATA3 interaction is important for the repression of genes associated with triple-negative and basal-like breast cancer (BLBCs) including FOXC1, and that GATA3 interacts with a C-terminal region of BRCA1. We demonstrate that FOXC1 is an essential survival factor maintaining the proliferation of BLBCs cell lines. We define the mechanistic basis of this corepression and identify the GATA3-binding site within the FOXC1 distal promoter region. We show that BRCA1 and GATA3 interact on the FOXC1 promoter and that BRCA1 requires GATA3 for recruitment to this region. This interaction requires fully functional BRCA1 as a mutant BRCA1 protein is unable to localize to the FOXC1 promoter or repress FOXC1 expression. We demonstrate that this BRCA1-GATA3 repression complex is not a FOXC1-specific phenomenon as a number of other genes associated with BLBCs such as FOXC2, CXCL1 and p-cadherin were also repressed in a similar manner. Finally, we demonstrate the importance of our findings by showing that loss of GATA3 expression or aberrant FOXC1 expression contributes to the drug resistance and epithelial-to-mesenchymal transition-like phenotypes associated with aggressive BLBCs.
Insights
Researchers discovered a new interaction between BRCA1 and GATA3 crucial for breast cancer repression. This BRCA1-GATA3 complex targets genes like FOXC1, impacting triple-negative breast cancer progression and drug resistance.
Area of Science:
- Molecular Biology
- Genetics
- Oncology
Background:
- BRCA1 is a critical tumor suppressor gene involved in DNA repair and differentiation.
- GATA3 is a transcription factor essential for mammary gland development.
- Triple-negative and basal-like breast cancers (BLBCs) are aggressive subtypes with limited therapeutic options.
Purpose of the Study:
- To elucidate the novel interaction between BRCA1 and GATA3.
- To determine the role of this interaction in the regulation of genes associated with BLBCs.
- To investigate the mechanistic basis of BRCA1-GATA3-mediated gene repression.
Main Methods:
- Co-immunoprecipitation assays to confirm BRCA1-GATA3 interaction.
- Chromatin immunoprecipitation (ChIP) to analyze promoter binding.
- Reporter assays and gene expression analysis to assess repression.
- Functional studies in BLBC cell lines.
Main Results:
- A novel interaction between BRCA1 and GATA3 was identified, crucial for normal breast differentiation.
- The BRCA1-GATA3 complex represses key genes in BLBCs, including FOXC1, which is vital for BLBC proliferation.
- BRCA1 requires GATA3 for recruitment to the FOXC1 promoter, and functional BRCA1 is necessary for repression.
- This repression mechanism extends to other BLBC-associated genes like FOXC2, CXCL1, and p-cadherin.
- Loss of GATA3 or aberrant FOXC1 expression correlates with drug resistance and epithelial-to-mesenchymal transition (EMT) phenotypes in aggressive BLBCs.
Conclusions:
- The BRCA1-GATA3 interaction is a critical regulatory mechanism in breast cancer, particularly in suppressing aggressive BLBC subtypes.
- Targeting the BRCA1-GATA3 pathway or modulating FOXC1 expression may offer new therapeutic strategies for BLBCs.
- Understanding this interaction provides insights into breast cancer progression, drug resistance, and EMT.
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