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Highly ordered spatial organization of the structural long noncoding NEAT1 RNAs within paraspeckle nuclear bodies.

ABSTRACT: Paraspeckles (PSPs) are nuclear bodies associated with the retention in the nucleus of specific mRNAs. Two isoforms of a long noncoding RNA (NEAT1_v1/Men? and NEAT1_v2/Men?) are required for the integrity of PSPs. Here, we analyzed the molecular organization of PSPs by immuno- and in situ hybridization electron microscopy. Detection of the paraspeckle markers PSPC1 and P54NRB/NONO confirm the identity between PSPs and the previously described interchromatin granule-associated zones (IGAZs). High-resolution in situ hybridization of NEAT1 transcripts revealed a highly ordered organization of IGAZ/PSPs. Although the 3.7-kb NEAT1_v1 and the identical 5' end of the 22.7-kb NEAT1_v2 transcripts are confined to the periphery, central sequences of NEAT1_v2 are found within the electron-dense core of the bodies. Moreover, the 3' end of NEAT1_v2 also localize to the periphery, indicating possible architectures for IGAZ/PSPs. These results further suggest that the organization of NEAT1 transcripts constrains the geometry of these bodies. Accordingly, we observed in HeLa and NIH 3T3 cells that IGAZ/PSPs are elongated structures with a well-defined diameter. Our results provide new insight on the ability of noncoding RNAs to form subcellular structures.

SUBMITTER: Souquere S

PROVIDER: S-EPMC2982136 | biostudies-literature | 2010 Nov

REPOSITORIES: biostudies-literature

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Highly ordered spatial organization of the structural long noncoding NEAT1 RNAs within paraspeckle nuclear bodies.

Souquere Sylvie S Beauclair Guillaume G Harper Francis F Fox Archa A Pierron Gérard G

Molecular biology of the cell 20100929 22

Paraspeckles (PSPs) are nuclear bodies associated with the retention in the nucleus of specific mRNAs. Two isoforms of a long noncoding RNA (NEAT1_v1/Menε and NEAT1_v2/Menβ) are required for the integrity of PSPs. Here, we analyzed the molecular organization of PSPs by immuno- and in situ hybridization electron microscopy. Detection of the paraspeckle markers PSPC1 and P54NRB/NONO confirm the identity between PSPs and the previously described interchromatin granule-associated zones (IGAZs). High ...[more]

PMID: 20881053

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Project description:Background: Hepatocellular Carcinoma (HCC) is a major form of liver cancer and a leading cause of cancer-related death worldwide. New insights into HCC pathobiology and mechanism of drug actions are urgently needed to improve patient outcomes. HCC undergoes metabolic reprogramming of glucose metabolism from respiration to aerobic glycolysis, a phenomenon known as the 'Warburg Effect' that supports rapid cancer cell growth, survival, and invasion. mTOR is known to promote Warburg Effect, but the underlying mechanism(s) remains poorly defined. The aim of this study is to understand the mechanism(s) and significance of mTOR regulation of aerobic glycolysis in HCC. Methods: We profiled mTORC1-dependent long non-coding RNAs (lncRNAs) by RNA-seq of HCC cells treated with rapamycin. Chromatin immunoprecipitation (ChIP) and luciferase reporter assays were used to explore the transcriptional regulation of NEAT1 by mTORC1. [U-13C]-glucose labeling and metabolomic analysis, extracellular acidification Rate (ECAR) by Seahorse XF Analyzer, and glucose uptake assay were used to investigate the role of mTOR-NEAT1-NONO signaling in the regulation of aerobic glycolysis. RNA immunoprecipitation (RIP) and NONO-binding motif scanning were performed to identify the regulatory mechanism of pre-mRNA splicing by mTOR-NEAT1. Myristoylated AKT1 (mAKT1)/NRASV12-driven HCC model developed by hydrodynamic transfection (HDT) was employed to explore the significance of mTOR-NEAT1 signaling in HCC tumorigenesis and mTOR-targeted therapy. Results: mTOR regulates lncRNA transcriptome in HCC and that NEAT1 is a major mTOR transcriptional target. Interestingly, although both NEAT1_1 and NEAT1_2 are down-regulated in HCC, only NEAT1_2 is significantly correlated with poor overall survival of HCC patients. NEAT1_2 is the organizer of nuclear paraspeckles that sequester the RNA-binding proteins NONO and SFPQ. We show that upon oncogenic activation, mTORC1 suppresses NEAT1_2 expression and paraspeckle biogenesis, liberating NONO/SFPQ, which in turn, binds to U5 within the spliceosome, stimulating mRNA splicing and expression of key glycolytic enzymes. This series of actions lead to enhanced glucose transport, aerobic glycolytic flux, lactate production, and HCC growth both in vitro and in vivo. Furthermore, the paraspeckle-mediated mechanism is important for the anticancer action of US FDA-approved drugs rapamycin/temsirolimus. Conclusions: These findings reveal a molecular mechanism by which mTOR promotes the 'Warburg Effect', which is important for the metabolism and development of HCC, and anticancer response of mTOR-targeted therapy.

Project description:Long noncoding RNAs (lncRNAs) are important regulators of chromatin; however, the mechanistic roles for many lncRNAs are poorly understood in part because their direct interactions with genomic loci and proteins are difficult to assess. We used CHART-seq to map the genomic binding sites for two highly expressed human lncRNAs, NEAT1 and MALAT1, which localize within the nucleus to paraspeckles and nuclear speckles, respectively. We show that NEAT1 and MALAT1 localize to hundreds of genomic sites in human cells, primarily over active genes. NEAT1 and MALAT1 exhibit colocalization to many of these loci, but display distinct gene body binding patterns at these sites, suggesting independent but complementary functions for these RNAs. Protein mass spectrometry analysis of CHART-enriched material (CHART-MS) identified numerous proteins enriched by both lncRNAs, supporting complementary binding and function, in addition to unique associated proteins. Transcriptional inhibition or stimulation affects the localization of NEAT1 to active chromatin sites, implying that DNA sequence itself does not target NEAT1 to chromatin and that localization responds to cues involved in the transcription process. Paired-end CHART-seq was performed for a single replicate of each capture oligonucleotide in untreated MCF-7 cells to establish binding sites of these RNAs, for a total of 6 samples. To investigate the effects of transcriptional inhibition and E2 stimulation on the localization of these RNAs, we performed paired-end CHART-seq with each capture oligonucleotide for two biological replicates of flavopiridol- and vehicle (DMSO)-treated MCF-7 cells and for two biological replicates of E2- and vehicle (ethanol)-treated MCF-7 cells. To establish the overlap of NEAT1 and MALAT1 binding sites with a known component of paraspeckles (NEAT1-containing subnuclear body), we performed paired-end ChIP-seq for the paraspeckle component PSF in MCF-7 cells, as well as a single-end biological replicate.

Dataset Information

Highly ordered spatial organization of the structural long noncoding NEAT1 RNAs within paraspeckle nuclear bodies.

Publications

Highly ordered spatial organization of the structural long noncoding NEAT1 RNAs within paraspeckle nuclear bodies.

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