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MTA1-mediated transcriptional repression of BRCA1 tumor suppressor gene.

ABSTRACT: Metastasis-associated tumor antigen 1 (MTA1), a component of the nucleosome remodeling and deacetylating (NuRD) complex is routinely upregulated in several cancers. In the present study, we investigated the potential role of MTA1 in BRCA1 transcriptional repression and subsequent chromosomal instability. MTA1-NuRD complex was found to negatively regulate BRCA1 transcription by physically associating with an atypical estrogen-responsive element (ERE) on the BRCA1 promoter. Moreover, MTA1 and HDAC complex recruited to the ERE of BRCA1 promoter in an ER alpha-dependent manner. Accordingly, BRCA1 protein levels were enhanced by silencing of either MTA1 expression or by treatment with the specific histone deacetylase inhibitor trichostatin A. MTA1's strong repressive effects on BRCA1 expression was supported by our observation that cells stably overexpressing MTA1 showed centrosome amplification which has been long implicated as a phenotype for BRCA1 repression. Accordingly, overexpression of BRCA1 in cells stably over expressing MTA1 resulted in restoration of normal centrosome numbers. Together, these findings strongly implicate MTA1 in the transcriptional repression of BRCA1 leading to abnormal centrosome number and chromosomal instability.

SUBMITTER: Molli PR

PROVIDER: S-EPMC2705285 | biostudies-literature | 2008 Mar

REPOSITORIES: biostudies-literature

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MTA1-mediated transcriptional repression of BRCA1 tumor suppressor gene.

Molli P R PR Singh R R RR Lee S W SW Kumar R R

Oncogene 20071008 14

Metastasis-associated tumor antigen 1 (MTA1), a component of the nucleosome remodeling and deacetylating (NuRD) complex is routinely upregulated in several cancers. In the present study, we investigated the potential role of MTA1 in BRCA1 transcriptional repression and subsequent chromosomal instability. MTA1-NuRD complex was found to negatively regulate BRCA1 transcription by physically associating with an atypical estrogen-responsive element (ERE) on the BRCA1 promoter. Moreover, MTA1 and HDAC ...[more]

PMID: 17922032

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Project description:BackgroundSIX homeobox 3 (SIX3) is a member of the sine oculis homeobox transcription factor family. It plays a vital role in the nervous system development. Our previous study showed that the SIX3 gene is hypermethylated, and its expression is decreased in astrocytoma, but the role of SIX3 remains unknown.MethodsChromatin-immunoprecipitation (ChIP) and luciferase reporter assay were used to confirm the binding of SIX3 to the promoter regions of aurora kinase A (AURKA) and aurora kinase B (AURKB). Confocal imaging and co-immunoprecipitation (Co-IP) were used to detect the interaction between AURKA and AURKB. Flow cytometry was performed to assess the effect of SIX3 on cell cycle distribution. Colony formation, EdU incorporation, transwell, and intracranial xenograft assays were performed to demonstrate the effect of SIX3 on the malignant phenotype of astrocytoma cells.ResultsSIX3 is identified as a novel negative transcriptional regulator of AURKA and AURKB, and it decreases the expression of AURKA and AURKB in a dose-dependent manner in astrocytoma cells. Importantly, interactions between AURKA and AURKB stabilize and protect AURKA/B from degradation, and overexpression of SIX3 does not affect these interactions; SIX3 also acts as a tumor suppressor, and it increases p53 activity and expression at the post-translational level by the negative regulation of AURKA or AURKB, reduces the events of numerical centrosomal aberrations and misaligned chromosomes, and significantly inhibits the proliferation, invasion, and tumorigenesis of astrocytoma in vitro and in vivo. Moreover, experiments using primary cultured astrocytoma cells indicate that astrocytoma patients with a low expression of SIX3 and mutant p53 are more sensitive to treatment with aurora kinase inhibitors.ConclusionSIX3 is a novel negative transcriptional regulator and acts as a tumor suppressor that directly represses the transcription of AURKA and AURKB in astrocytoma. For the first time, the functional interaction of AURKA and AURKB has been found, which aids in the protection of their stability, and partially explains their constant high expression and activity in cancers. SIX3 is a potential biomarker that could be used to predict the response of astrocytoma patients to aurora kinase inhibitors.

Project description:IntroductionBreast cancer is a worldwide health problem and the leading cause of cancer death among females. We previously identified Jumonji domain containing 2A (JMJD2A) as a critical mediator of breast cancer proliferation, migration and invasion. We now report that JMJD2A could promote breast cancer progression through transcriptional repression of the tumor suppressor aplasia Ras homolog member I (ARHI).MethodsImmunohistochemistry was performed to examine protein expressions in 155 cases of breast cancer and 30 non-neoplastic tissues. Spearman correlation analysis was used to analyze the correlation between JMJD2A expression and clinical parameters as well as several tumor regulators in 155 cases of breast cancer. Gene and protein expressions were monitored by quantitative polymerase chain reaction (qPCR) and Western blot. Results from knockdown of JMJD2A, overexpression of JMJD2A, Co-immunoprecipitation (Co-IP) assay, dual luciferase reporter gene assay and chromatin immunoprecipitation (ChIP) elucidated molecular mechanisms of JMJD2A action in breast cancer progression. Furthermore, the effects of ARHI overexpression on JMJD2A-mediated tumor progression were investigated in vitro and in vivo. For in vitro experiments, cell proliferation, wound-healing, migration and invasion were monitored by cell counting, scratch and Boyden Chamber assays. For in vivo experiments, control cells and cells stably expressing JMJD2A alone or together with ARHI were inoculated into mammary fat pads of mice. Tumor volume, tumor weight and metastatic nodules were measured by caliper, electronic balance and nodule counting, respectively.ResultsJMJD2A was highly expressed in human breast cancers and positively correlated with tumor progression. Knockdown of JMJD2A increased ARHI expression whereas overexpression of JMJD2A decreased ARHI expression at both protein and mRNA levels. Furthermore, E2Fs and histone deacetylases were involved in the transcriptional repression of ARHI expression by JMJD2A. And the aggressive behavior of JMJD2A in breast cancers could be reversed by re-expression of ARHI in vitro and in vivo.ConclusionWe demonstrated a cancer-promoting effect of JMJD2A and defined a novel molecular pathway contributing to JMJD2A-mediated breast cancer progression.

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MTA1-mediated transcriptional repression of BRCA1 tumor suppressor gene.

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MTA1-mediated transcriptional repression of BRCA1 tumor suppressor gene.

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