Abstract
Purpose
We previously reported that BRCA1 interacts with aryl hydrocarbon receptor nuclear translocator (ARNT) and that this interaction affects TCDD-induced CYP1A1 gene expression (Kang et al., J Biol Chem 281:14654–14662, 2006). In this study we continue this investigation and begin to define the significance of this interaction for the regulation of stress-induced transcription.
Methods
Immunoprecipitations (IPs), western blot (WB) analysis, GST pull-down assays and promoter reporter assays were used to investigate whether the aryl hydrocarbon receptor (AhR) can regulate transcription that is dependent on the activation domain 1 (AD1) domain of BRCA1.
Results
We show that AhR, a transcription factor, can bind specifically to AD1 in the C-terminal region of BRCA1 and affect BRCA1’s ability to regulate transcription activity. We found that xenobiotics that positively and negatively affect AhR’s activity as a transcription factor (e.g., dioxin and α-naphthoflavone, respectively), have similar effects on AhR’s ability to affect AD1-domain-dependent transcription. These physical and functional AhR–AD1 interactions may require the coiled-coil motif in AD1 because point-mutations in this motif reduce these interactions.
Conclusion
Xenobiotic-activated AhR can function in two ways, as a component of the AhR/ARNT transcription factor and a regulator of AD1-dependent transcription. Consequently, BRCA1 has two distinct mechanisms for sensing xenobiotics and regulating AhR-dependent stress responses to these xenobiotics. We speculate that the normal functioning of this interaction could play a role in BRCA1’s tumor suppressing ability.
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Abbreviations
- ARNT:
-
Aryl hydrocarbon receptor nuclear translocator
- AhR:
-
Aryl hydrocarbon receptor
- BRCA1:
-
Breast cancer susceptibility gene-1
- DMEM:
-
Dulbecco’s modified eagles’ medium
- DMSO:
-
Dimethyl sulfoxide
- FBS:
-
Fetal bovine serum
- IP:
-
Immunoprecipitation
- SEM:
-
Standard error of mean
- WB:
-
Western blot
- AD1:
-
Activation domain 1
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Acknowledgments
Dr. Bae has been supported, in part, by the National Institute of Environmental Health Science, NIH (ES01440-01) and the Susan G. Komen Foundation for the Cure (BCTR119906 and FAS0703858). Drs. Li and Hu have been supported by CA93506 (R. L) and CA118578 (Y. H), respectively. We appreciate Drs. Albert J. Fornace Jr. and Thomas L. Mattson for helpful discussions.
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Kang, H.J., Kim, H.J., Cho, CH. et al. BRCA1 transcriptional activity is enhanced by interactions between its AD1 domain and AhR. Cancer Chemother Pharmacol 62, 965–975 (2008). https://doi.org/10.1007/s00280-008-0686-x
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DOI: https://doi.org/10.1007/s00280-008-0686-x