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The FOXN3-NEAT1-SIN3A repressor complex promotes progression of hormonally responsive breast cancer.

ABSTRACT: The pathophysiological function of the forkhead transcription factor FOXN3 remains to be explored. Here we report that FOXN3 is a transcriptional repressor that is physically associated with the SIN3A repressor complex in estrogen receptor-positive (ER+) cells. RNA immunoprecipitation-coupled high-throughput sequencing identified that NEAT1, an estrogen-inducible long noncoding RNA, is required for FOXN3 interactions with the SIN3A complex. ChIP-Seq and deep sequencing of RNA genomic targets revealed that the FOXN3-NEAT1-SIN3A complex represses genes including GATA3 that are critically involved in epithelial-to-mesenchymal transition (EMT). We demonstrated that the FOXN3-NEAT1-SIN3A complex promotes EMT and invasion of breast cancer cells in vitro as well as dissemination and metastasis of breast cancer in vivo. Interestingly, the FOXN3-NEAT1-SIN3A complex transrepresses ER itself, forming a negative-feedback loop in transcription regulation. Elevation of both FOXN3 and NEAT1 expression during breast cancer progression corresponded to diminished GATA3 expression, and high levels of FOXN3 and NEAT1 strongly correlated with higher histological grades and poor prognosis. Our experiments uncovered that NEAT1 is a facultative component of the SIN3A complex, shedding light on the mechanistic actions of NEAT1 and the SIN3A complex. Further, our study identified the ER?-NEAT1-FOXN3/NEAT1/SIN3A-GATA3 axis that is implicated in breast cancer metastasis, providing a mechanistic insight into the pathophysiological function of FOXN3.

SUBMITTER: Li W

PROVIDER: S-EPMC5669564 | biostudies-literature | 2017 Sep

REPOSITORIES: biostudies-literature

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The FOXN3-NEAT1-SIN3A repressor complex promotes progression of hormonally responsive breast cancer.

Li Wanjin W Zhang Zihan Z Liu Xinhua X Cheng Xiao X Zhang Yi Y Han Xiao X Zhang Yu Y Liu Shumeng S Yang Jianguo J Xu Bosen B He Lin L Sun Luyang L Liang Jing J Shang Yongfeng Y

The Journal of clinical investigation 20170814 9

The pathophysiological function of the forkhead transcription factor FOXN3 remains to be explored. Here we report that FOXN3 is a transcriptional repressor that is physically associated with the SIN3A repressor complex in estrogen receptor-positive (ER+) cells. RNA immunoprecipitation-coupled high-throughput sequencing identified that NEAT1, an estrogen-inducible long noncoding RNA, is required for FOXN3 interactions with the SIN3A complex. ChIP-Seq and deep sequencing of RNA genomic targets rev ...[more]

PMID: 28805661

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Project description:The forkhead box (FOX) family of proteins is composed of more than 50 members that are phylogenetically classified into 19 subclasses (A to S). These transcription factors all share a homology in their DNA-binding domain, the forkhead domain, also known as winged helix due to its butterfly-like structural appearance.FOX proteins have been implicated in a broad spectrum of cellular processes including cell proliferation, differentiation, DNA repair, metabolism, and aging. However, the biological function of the mammalian forkhead transcription factors of the N class including FOXN3 remains to be investigated. The SIN3A complex is a large protein assembly consisting of over a dozen of proteins including SIN3A, HDAC1/2, RBBP4/7 and etc. This complex is recruited by multiple transcription repressors and impacts on multifaceted biological functions ranging from development, differentiation, and senescence to oncogenic transformation. Long noncoding RNAs (lncRNAs) are a class of noncoding RNAs that are over 200 nucleotides in length. In the past years, these molecules have emerged as important components of the epigenetic regulatory network to influence transcription as well as other nuclear activities, and their dysregulation underlies several pathologic states including cancer. One of the lncRNAs, NEAT1 (nuclear paraspeckle assembly transcript 1), is a highly abundant lncRNA initially described as a structural component of nuclear paraspeckles. Subsequent studies suggest that NEAT1 also influences transcription through either an indirect mechanism or a direct way. In this study, we investigated the function and the underlying mechanism of FOXN3 in breast cancer cells. We showed that FOXN3 is physically associated with the SIN3A complex and identified that NEAT1, which is induced by estrogen in breast cancer cells, is required for this interaction. We analyzed the genomic targets of the FOXN3/SIN3A/NEAT1 complex and demonstrated that estrogen receptor (ER) itself is regulated, through negative feedback, by the FOXN3/SIN3A/NEAT1 complex. We investigated the role of the FOXN3/SIN3A/NEAT1 complex in breast cancer metastasis and explored the clinicopathological significance of the ER-NEAT1-FOXN3/NEAT1/SIN3A-GATA3 axis in breast cancer.

Project description:BackgroundSin3A is an evolutionarily conserved transcriptional repressor which regulates gene expression as part of the multi-protein Sin3 repressive complex. It functions as a scaffold upon which proteins with enzymatic activity dock, including chromatin modifying histone deacetylases. Although regulation of transcription by Sin3A has been studied in detail, little is understood about the function of Sin3A in cancer cells. We previously showed that Sin3A is expressed in breast cancer cells and is a repressor of estrogen receptor-alpha (ERα, ESR1) gene expression. Here, we expand our previous studies to elucidate the function of Sin3A in the control of gene expression and growth of breast cancer cells.ResultsAnalysis of gene expression following knockdown of Sin3A revealed changes in both basal and regulated gene transcription. Genes of known importance in breast cancer and estrogen signaling, including ERBB2, PGR, MYC, CLU, and NCOA2, were among those identified as Sin3A-responsive. The mechanism of Sin3A action varied among genes and was found to be mediated through both HDAC1/2 -dependent and -independent activities. Loss of Sin3A inhibited breast cancer cell growth by increasing apoptosis without affecting cell cycle progression. Analysis of both ERα-positive and ERα-negative cell lines revealed that the effects of Sin3A on growth were cell-type specific, as Sin3A expression promoted maximum growth of only the ERα-positive cells, and, notably, Sin3A protein itself was increased by estrogen. Further gene expression experiments revealed that Sin3A repressed expression of key apoptotic genes, including TRAIL, TRAILR1, CASP10, and APAF1, in ERα-positive, but not ERα-negative, cell lines, which could provide a mechanistic explanation for cell-type differences in growth.ConclusionsThis study identifies Sin3A as a regulator of gene expression, survival, and growth in ERα-positive breast cancer cells. Sin3A regulates the transcription of genes involved in breast cancer and apoptosis and acts through multiple mechanisms not limited to histone deacetylase function. These findings reveal previously undescribed functions of Sin3A in breast cancer and provide evidence for an important role of this transcriptional repressor in ERα-positive tumor cell growth.

Dataset Information

The FOXN3-NEAT1-SIN3A repressor complex promotes progression of hormonally responsive breast cancer.

Publications

The FOXN3-NEAT1-SIN3A repressor complex promotes progression of hormonally responsive breast cancer.

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