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c-Myc activates BRCA1 gene expression through distal promoter elements in breast cancer cells

BACKGROUND: The BRCA1 gene plays an important role in the maintenance of genomic stability. BRCA1 inactivation contributes to breast cancer tumorigenesis. An increasing number of transcription factors have been shown to regulate BRCA1 expression. c-Myc can act as a transcriptional activator, regulat...

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Autores principales: Chen, Yinghua, Xu, Jinhua, Borowicz, Stanley, Collins, Cindy, Huo, Dezheng, Olopade, Olufunmilayo I
Formato: Online Artículo Texto
Lenguaje:English
Publicado: BioMed Central 2011
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3141769/
https://www.ncbi.nlm.nih.gov/pubmed/21668996
http://dx.doi.org/10.1186/1471-2407-11-246
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author Chen, Yinghua
Xu, Jinhua
Borowicz, Stanley
Collins, Cindy
Huo, Dezheng
Olopade, Olufunmilayo I
author_facet Chen, Yinghua
Xu, Jinhua
Borowicz, Stanley
Collins, Cindy
Huo, Dezheng
Olopade, Olufunmilayo I
author_sort Chen, Yinghua
collection PubMed
description BACKGROUND: The BRCA1 gene plays an important role in the maintenance of genomic stability. BRCA1 inactivation contributes to breast cancer tumorigenesis. An increasing number of transcription factors have been shown to regulate BRCA1 expression. c-Myc can act as a transcriptional activator, regulating up to 15% of all genes in the human genome and results from a high throughput screen suggest that BRCA1 is one of its targets. In this report, we used cultured breast cancer cells to examine the mechanisms of transcriptional activation of BRCA1 by c-Myc. METHODS: c-Myc was depleted using c-Myc-specific siRNAs in cultured breast cancer cells. BRCA1 mRNA expression and BRCA1 protein expression were determined by quantitative RT-PCR and western blot, respectively and BRCA1 promoter activities were examined under these conditions. DNA sequence analysis was conducted to search for high similarity to E boxes in the BRCA1 promoter region. The association of c-Myc with the BRCA1 promoter in vivo was tested by a chromatin immunoprecipitation assay. We investigated the function of the c-Myc binding site in the BRCA1 promoter region by a promoter assay with nucleotide substitutions in the putative E boxes. BRCA1-dependent DNA repair activities were measured by a GFP-reporter assay. RESULTS: Depletion of c-Myc was found to be correlated with reduced expression levels of BRCA1 mRNA and BRCA1 protein. Depletion of c-Myc decreased BRCA1 promoter activity, while ectopically expressed c-Myc increased BRCA1 promoter activity. In the distal BRCA1 promoter, DNA sequence analysis revealed two tandem clusters with high similarity, and each cluster contained a possible c-Myc binding site. c-Myc bound to these regions in vivo. Nucleotide substitutions in the c-Myc binding sites in these regions abrogated c-Myc-dependent promoter activation. Furthermore, breast cancer cells with reduced BRCA1 expression due to depletion of c-Myc exhibited impaired DNA repair activity. CONCLUSIONS: The distal BRCA1 promoter region is associated with c-Myc and contributes to BRCA1 gene activation.
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spelling pubmed-31417692011-07-23 c-Myc activates BRCA1 gene expression through distal promoter elements in breast cancer cells Chen, Yinghua Xu, Jinhua Borowicz, Stanley Collins, Cindy Huo, Dezheng Olopade, Olufunmilayo I BMC Cancer Research Article BACKGROUND: The BRCA1 gene plays an important role in the maintenance of genomic stability. BRCA1 inactivation contributes to breast cancer tumorigenesis. An increasing number of transcription factors have been shown to regulate BRCA1 expression. c-Myc can act as a transcriptional activator, regulating up to 15% of all genes in the human genome and results from a high throughput screen suggest that BRCA1 is one of its targets. In this report, we used cultured breast cancer cells to examine the mechanisms of transcriptional activation of BRCA1 by c-Myc. METHODS: c-Myc was depleted using c-Myc-specific siRNAs in cultured breast cancer cells. BRCA1 mRNA expression and BRCA1 protein expression were determined by quantitative RT-PCR and western blot, respectively and BRCA1 promoter activities were examined under these conditions. DNA sequence analysis was conducted to search for high similarity to E boxes in the BRCA1 promoter region. The association of c-Myc with the BRCA1 promoter in vivo was tested by a chromatin immunoprecipitation assay. We investigated the function of the c-Myc binding site in the BRCA1 promoter region by a promoter assay with nucleotide substitutions in the putative E boxes. BRCA1-dependent DNA repair activities were measured by a GFP-reporter assay. RESULTS: Depletion of c-Myc was found to be correlated with reduced expression levels of BRCA1 mRNA and BRCA1 protein. Depletion of c-Myc decreased BRCA1 promoter activity, while ectopically expressed c-Myc increased BRCA1 promoter activity. In the distal BRCA1 promoter, DNA sequence analysis revealed two tandem clusters with high similarity, and each cluster contained a possible c-Myc binding site. c-Myc bound to these regions in vivo. Nucleotide substitutions in the c-Myc binding sites in these regions abrogated c-Myc-dependent promoter activation. Furthermore, breast cancer cells with reduced BRCA1 expression due to depletion of c-Myc exhibited impaired DNA repair activity. CONCLUSIONS: The distal BRCA1 promoter region is associated with c-Myc and contributes to BRCA1 gene activation. BioMed Central 2011-06-13 /pmc/articles/PMC3141769/ /pubmed/21668996 http://dx.doi.org/10.1186/1471-2407-11-246 Text en Copyright ©2011 Chen et al; licensee BioMed Central Ltd. http://creativecommons.org/licenses/by/2.0 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
spellingShingle Research Article
Chen, Yinghua
Xu, Jinhua
Borowicz, Stanley
Collins, Cindy
Huo, Dezheng
Olopade, Olufunmilayo I
c-Myc activates BRCA1 gene expression through distal promoter elements in breast cancer cells
title c-Myc activates BRCA1 gene expression through distal promoter elements in breast cancer cells
title_full c-Myc activates BRCA1 gene expression through distal promoter elements in breast cancer cells
title_fullStr c-Myc activates BRCA1 gene expression through distal promoter elements in breast cancer cells
title_full_unstemmed c-Myc activates BRCA1 gene expression through distal promoter elements in breast cancer cells
title_short c-Myc activates BRCA1 gene expression through distal promoter elements in breast cancer cells
title_sort c-myc activates brca1 gene expression through distal promoter elements in breast cancer cells
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3141769/
https://www.ncbi.nlm.nih.gov/pubmed/21668996
http://dx.doi.org/10.1186/1471-2407-11-246
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