RESUMO
MCF7 cells acquire estrogen-independent proliferation after long-term estrogen deprivation (LTED), which recapitulates endocrine therapy resistance. LTED cells can become primed for apoptosis, but the underlying mechanism is largely unknown. We previously reported that Eleanor non-coding RNAs (ncRNAs) upregulate the ESR1 gene in LTED cells. Here, we show that Eleanors delineate the topologically associating domain (TAD) of the ESR1 locus in the active nuclear compartment of LTED cells. The TAD interacts with another transcriptionally active TAD, which is 42.9 Mb away from ESR1 and contains a gene encoding the apoptotic transcription factor FOXO3. Inhibition of a promoter-associated Eleanor suppresses all genes inside the Eleanor TAD and the long-range interaction between the two TADs, but keeps FOXO3 active to facilitate apoptosis in LTED cells. These data indicate a role of ncRNAs in chromatin domain regulation, which may underlie the apoptosis-prone nature of therapy-resistant breast cancer cells and could be good therapeutic targets.
Assuntos
Apoptose/genética , Neoplasias da Mama/genética , Receptor alfa de Estrogênio/genética , Regulação Neoplásica da Expressão Gênica , RNA não Traduzido/metabolismo , Antineoplásicos Hormonais/farmacologia , Antineoplásicos Hormonais/uso terapêutico , Apoptose/efeitos dos fármacos , Inibidores da Aromatase/farmacologia , Inibidores da Aromatase/uso terapêutico , Sítios de Ligação/genética , Neoplasias da Mama/tratamento farmacológico , Neoplasias da Mama/patologia , Cromatina/genética , Cromatina/metabolismo , Resistencia a Medicamentos Antineoplásicos/genética , Epigênese Genética , Receptor alfa de Estrogênio/metabolismo , Estrogênios/metabolismo , Feminino , Proteína Forkhead Box O3/genética , Proteína Forkhead Box O3/metabolismo , Loci Gênicos/genética , Sequenciamento de Nucleotídeos em Larga Escala , Humanos , Células MCF-7 , Regiões Promotoras Genéticas/genética , Regulação para CimaRESUMO
Combined small-cell lung carcinoma (cSCLC) is composed of small-cell lung carcinoma (SCLC) admixed with non-small-cell lung carcinoma (NSCLC). Evaluating the molecular differences between SCLC and NSCLC could lead to a better understanding of the pathogenesis of such neoplasms. Therefore, in this study, we investigated the correlation between histone acetylation and Notch1 expression in lung carcinoma. Using chromatin immunoprecipitation (ChIP) assay, we measured the level of acetylated histone H3 around the promoter region of Notch1 in SCLC and NSCLC cells. We then treated SCLC cells with trichostatin A (TSA) and characterized the level of histone H3 acetylation at Notch1. In addition, TSA-treated cells were injected into immune-compromised mice, for analysis of the ex vivo tumor xenograft phenotype. The level of acetylated histone H3 surrounding the Notch1 promoter was lower in lung cancer cells not expressing Notch1. Tumors originated from TSA-treated SCLC cells occasionally formed an epithelial-like glandular arrangement of cells; with Notch1 expression and decreased expression of neuroendocrine (NE) markers. Histone deacetylation around the promoter region of Notch1 inhibits Notch1 protein expression in SCLC and the restoration of Notch1 expression in SCLC leads to the concurrent appearance of epithelial-like areas within the SCLC, which could provide a possible mechanism for histogenesis of cSCLC.
Assuntos
Histonas/metabolismo , Neoplasias Pulmonares/metabolismo , Receptor Notch1/metabolismo , Carcinoma de Pequenas Células do Pulmão/metabolismo , Acetilação , Linhagem Celular Tumoral , HumanosRESUMO
The cell nucleus is highly organized and functionally compartmentalized. Double-stranded naked DNA is complexed with core histones and assembled into nucleosomes and chromatin, which are surrounded by nuclear domains composed of RNAs and proteins. Recently, three-dimensional views of chromosome organization beyond the level of the nucleosome have been established and are composed of several layers of chromosome domains. Only a small portion of the human genome encodes proteins; the majority is pervasively transcribed into noncoding RNAs whose functions are under intensive investigation. Importantly, the questions of how nuclear retained noncoding RNAs play roles in orchestrating the chromatin structure that have been addressed. We discuss the novel noncoding RNA clusters, Eleanors, which are derived from a large chromatin domain. They accumulate at the site of their own transcription to form RNA clouds in the nucleus, and they activate gene expression in the chromatin domain. Noncoding RNAs have emerging roles in genome regulation that are integrated into the spatial organization of chromatin and the nucleus. WIREs RNA 2017, 8:e1384. doi: 10.1002/wrna.1384 For further resources related to this article, please visit the WIREs website.
Assuntos
Núcleo Celular/genética , Cromatina/genética , Cromossomos/genética , Histonas/metabolismo , RNA Longo não Codificante/genética , Animais , HumanosRESUMO
Estrogen receptor-α (ER)-positive breast cancer cells undergo hormone-independent proliferation after deprivation of oestrogen, leading to endocrine therapy resistance. Up-regulation of the ER gene (ESR1) is critical for this process, but the underlying mechanisms remain unclear. Here we show that the combination of transcriptome and fluorescence in situ hybridization analyses revealed that oestrogen deprivation induced a cluster of noncoding RNAs that defined a large chromatin domain containing the ESR1 locus. We termed these RNAs as Eleanors (ESR1 locus enhancing and activating noncoding RNAs). Eleanors were present in ER-positive breast cancer tissues and localized at the transcriptionally active ESR1 locus to form RNA foci. Depletion of one Eleanor, upstream (u)-Eleanor, impaired cell growth and transcription of intragenic Eleanors and ESR1 mRNA, indicating that Eleanors cis-activate the ESR1 gene. Eleanor-mediated gene activation represents a new type of locus control mechanism and plays an essential role in the adaptation of breast cancer cells.
