BRCA1 Represses Amphiregulin Gene Expression

Department of Pathology, Harvard Medical School and Brigham and Women's Hospital, Boston, Massachusetts, USA.
Cancer Research (Impact Factor: 9.33). 02/2010; 70(3):996-1005. DOI: 10.1158/0008-5472.CAN-09-2842
Source: PubMed


BRCA1, the breast cancer- and ovarian cancer-specific tumor suppressor, can be a transcriptional repressor or a transcriptional activator, depending on the promoter context. To identify the genes activated or repressed by BRCA1, we have analyzed microarray results from cells depleted of BRCA1 and revealed a number of genes regulated by BRCA1 on the level of transcription. Among the genes repressed by BRCA1, we have identified amphiregulin (AREG) and early growth response-1 (EGR1). Results indicate that BRCA1 regulates AREG transcription directly through binding to the AREG promoter, however, we could not detect BRCA1 on the EGR1 promoter, suggesting that EGR1 is indirectly regulated by BRCA1. In an attempt to identify the mechanism of the AREG transcriptional repression by BRCA1, we have mapped two independent BRCA1 response elements on the AREG located at positions -202/-182 and +19/+122. BRCA1 depletion leads to induction of the AREG protein. Taken together, our data build the connection between BRCA1 loss of function and AREG upregulation-a change in gene expression often observed in breast cancer.

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Available from: Andrew Horwitz, Jun 02, 2015
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    • "In addition to this ‘indirect’ role in transcriptional regulation, BRCA1 has been identified on a number of target gene promoters where it directly influences gene expression (9–13). Given BRCA1's lack of sequence-specific DNA binding, BRCA1 is likely to be recruited to promoters by sequence-specific DNA binding TFs. "
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    ABSTRACT: A role for BRCA1 in the direct and indirect regulation of transcription is well established. However, a comprehensive view of the degree to which BRCA1 impacts transcriptional regulation on a genome-wide level has not been defined. We performed genome-wide expression profiling and ChIP-chip analysis, comparison of which revealed that although BRCA1 depletion results in transcriptional changes in 1294 genes, only 44 of these are promoter bound by BRCA1. However, 27% of these transcripts were linked to transcriptional regulation possibly explaining the large number of indirect transcriptional changes observed by microarray analysis. We show that no specific consensus sequence exists for BRCA1 DNA binding but rather demonstrate the presence of a number of known and novel transcription factor (TF)- binding sites commonly found on BRCA1 bound promoters. Co-immunoprecipitations confirmed that BRCA1 interacts with a number of these TFs including AP2-α, PAX2 and ZF5. Finally, we show that BRCA1 is bound to a subset of promoters of genes that are not altered by BRCA1 loss, but are transcriptionally regulated in a BRCA1-dependent manner upon DNA damage. These data suggest a model, whereby BRCA1 is present on defined promoters as part of an inactive complex poised to respond to various genotoxic stimuli.
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    • "Since TAG/MSG genes are postulated to encode for products involved in the cross-talk between the cancer cell and the tumor microenvironment [12,13], we selected five RNASET2-responsive genes, mainly because of of their involvement in cell adhesion and migration. The five selected genes are MDKN, encoding an angiogenic growth factor over-expressed in various human malignant tumors and recently suggested as a new biomarker for ovarian cancer [14-16]; AREG (cell invasion breast cancer), a regulator of cancer cells invasiveness which was reported to be frequently overexpressed in colon, breast, prostate, pancreas, lung and ovarian cancer [17-19]; MCAM, a well known marker of poor prognosis in epithelial ovarian cancer, whose gene product promotes the growth, invasion and metastasic potential of malignant cells [20-22]; PLAU (PLasminogen Activator Urokinase-type), which promotes fibrinolysis and degradation of extracellular matrix [23]; and NNMT (nicotinamide N-methyltransferase), a serum tumor marker for colorectal cancer recently identified as novel regulator of cell migration [24,25]. "
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    • "In fetal kidney differentiation, the zinc-finger transcription factor Wilms tumor suppressor (WT1) has been shown to regulate amphiregulin gene expression (Lee et al., 1999), but we did not find any WT1 expression in PHD2-and HIF-2-dependent regulation of amphiregulin MR Bordoli et al MCF-7 cells (data not shown). Recently, BRCA1 has been described as transcriptional repressor of amphiregulin and loss of BRCA1 resulted in elevated amphiregulin protein levels (Lamber et al., 2010). The role of oxygen in amphiregulin regulation is incompletely understood. "
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