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The lncRNA NEAT1_1 is seemingly dispensable for normal tissue homeostasis and cancer cell growth

ABSTRACT: NEAT1 is one of the most studied lncRNAs, in part because its silencing in mice causes defects in mammary gland development and corpus luteum formation and protects them from skin cancer development. Moreover, depleting NEAT1 in established cancer cell lines reduces growth and sensitizes cells to DNA damaging agents. However, NEAT1 produces two isoforms and because the short isoform, NEAT1_1, completely overlaps the 5' part of the long NEAT1_2 isoform, the respective contributions of each of the isoforms to these phenotypes has remained unclear. Whereas NEAT1_1 is highly expressed in most tissues, NEAT1_2 is the central architectural component of paraspeckles, which are nuclear bodies that assemble in specific tissues and cells exposed to various forms of stress. Using dual RNA-FISH to detect both NEAT1_1 outside of paraspeckles and NEAT1_2/NEAT1 inside this nuclear body, we report herein that NEAT1_1 levels are dynamically regulated during the cell cycle and targeted for degradation by the nuclear RNA exosome. Unexpectedly, however, cancer cells engineered to lack NEAT1_1, but not NEAT1_2, do not exhibit cell cycle defects. Moreover, Neat1_1-specific knockout mice do not exhibit the phenotypes observed in Neat1-deficient mice. We propose that NEAT1 functions are mainly, if not exclusively, attributable to NEAT1_2 and, by extension, to paraspeckles.

ORGANISM(S): Homo sapiens

PROVIDER: GSE137211 | GEO | 2019/09/11

REPOSITORIES: GEO

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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.

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The lncRNA NEAT1_1 is seemingly dispensable for normal tissue homeostasis and cancer cell growth

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