Direct RNA-RNA interaction between Neat1 and RNA targets, as a mechanism for RNAs paraspeckle retention
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ABSTRACT: The goal of this study was to determine if the lncRNA Neat1, in addition to its structural role, may also be directly involved in the binding by base pairing of RNAs and consequently in their retention in paraspeckles
Project description:The long non-coding RNA NEAT1 (nuclear enriched abundant transcript 1) nucleates the formation of paraspeckles, which constitute a type of nuclear body that has multiple roles in gene expression. How the NEAT1 gene itself is regulated and how paraspeckles communicate with other cell compartments remains poorly understood. Here we identify regulators of NEAT1 transcription using an endogenous NEAT1 promoter-driven EGFP reporter in human cells coupled with genome-wide RNAi screens. In addition to transcription factors and chromatin modulators, the screens unexpectedly yielded gene candidates involved in mitochondrial functions as essential regulators of NEAT1 expression and paraspeckle formation. Mitochondrial defects altered NEAT1 transcription via ATF2 and subsequently uncoupled 3’ end processing of NEAT1_1 from its long isoform to favour NEAT1_2 production, which is key for generating elongated paraspeckles that have different features from the regular, globular bodies. Correspondingly, NEAT1 depletion has profound effects on mitochondrial dynamics and function by altering sequestration of mRNAs of mitochondrial genes enriched in paraspeckles. Overall, our data provided a rich resource for understanding NEAT1 and paraspeckle regulation, and revealed an unexpected crosstalk between cytoplasmic organelles and nuclear bodies.
Project description:Paraspeckles are nuclear ribonucleic complex formed of a long non-coding RNA, nuclear-enriched abundant transcript one (Neat1) and associated RNA-binding proteins (RBP) whose cellular known functions are to sequester in the nucleus both proteins and RNAs. However, how RNAs are bound to paraspeckles is largely unknown. It is highly likely that binding of RNAs may occur via interactions with RBPs and accordingly, two structures present in the 3'UTR of some RNAs have been shown to allow their association to paraspeckles via protein binding. However, Neat1 could also be involved in the targeting of RNAs through direct RNA-RNA interactions. Using an RNA pull-down procedure adapted to select only RNAs engaged in direct RNA-RNA interactions and followed by RNA-seq we showed that in a rat pituitary cell line, GH4C1 cells, 1791 RNAs were associated with paraspeckles by direct interaction with Neat1. Neat1 was actually found able to bind more than 30% of the total transcripts targeted by the paraspeckles, we have identified in this cell line in a previous study. Furthermore, given the biological processes in which direct RNAs targets of Neat1 were involved as determined by gene ontology analysis, it was proposed that Neat1 played a major role in paraspeckle functions such as circadian rhythms, mRNA processing, RNA splicing and regulation of cell cycle. Finally, we provided evidence that direct RNA targets of Neat1 were preferentially bound to the 5' end of Neat1 demonstrating that they are located in the shell region of paraspeckles.
Project description:Although thousands of long non-coding RNAs (lncRNAs) are localized in the nucleus, only a few dozen have been functionally characterized. We found that nuclear paraspeckle assembly transcript 1 (NEAT1), an essential lncRNA for the formation of nuclear body paraspeckles, is induced by poly I:C stimulation, resulting in excess formation of paraspeckles. Using microarray analysis, we investigated whether NEAT1 induction followed by excess formation of paraspeckles was involved in poly I:C-inducible gene expression. We want to know the NEAT1-regulated genes. To the end, HeLa TO cells with and without poly I:C stimulation and NEAT1-knock down cells with and without poly I:C stimulation and cells transfected with mock plasmid or Neat1v2 expression plasmid alone were used for RNA extraction and hybridization on Affymetrix microarrays.
Project description:Type 2 Diabetes (T2D) is a global health issue characterized by abnormal blood glucose levels and often associated with excessive hepatic gluconeogenesis. Increased circulating non-essential amino acids (NEAAs) are consistently observed in T2D individuals; however, the specific contribution of each amino acid to T2D pathogenesis remains less understood. Here, we reported an unexpected role of the NEAA proline in coordinating hepatic glucose metabolism by modulating paraspeckle, a nuclear structure scaffolded by the long noncoding RNA Neat1. Mechanistically, proline diminished paraspeckles in hepatocytes, liberating the retained mRNA species into cytoplasm for translation, including the mRNAs of Ppargc1a and Foxo1, contributing to enhanced gluconeogenesis and hyperglycemia. We further demonstrated that the proline-paraspeckle-mRNA retention axis existed in diabetic liver samples, and intervening this axis via paraspeckle restoration significantly alleviated hyperglycemia in both female and male diabetic mouse models. Collectively, our results not only delineated a previously unappreciated proline-instigated, paraspeckle-dependent mRNA retention mechanism regulating gluconeogenesis, but also spotlighted proline and paraspeckle as potential targets for managing hyperglycemia. This SuperSeries is composed of the SubSeries listed below.
Project description:Type 2 Diabetes (T2D) is a global health issue characterized by abnormal blood glucose levels and often associated with excessive hepatic gluconeogenesis. Increased circulating non-essential amino acids (NEAAs) are consistently observed in T2D individuals; however, the specific contribution of each amino acid to T2D pathogenesis remains less understood. Here, we reported an unexpected role of the NEAA proline in coordinating hepatic glucose metabolism by modulating paraspeckle, a nuclear structure scaffolded by the long noncoding RNA Neat1. Mechanistically, proline diminished paraspeckles in hepatocytes, liberating the retained mRNA species into cytoplasm for translation, including the mRNAs of Ppargc1a and Foxo1, contributing to enhanced gluconeogenesis and hyperglycemia. We further demonstrated that the proline-paraspeckle-mRNA retention axis existed in diabetic liver samples, and intervening this axis via paraspeckle restoration significantly alleviated hyperglycemia in both female and male diabetic mouse models. Collectively, our results not only delineated a previously unappreciated proline-instigated, paraspeckle-dependent mRNA retention mechanism regulating gluconeogenesis, but also spotlighted proline and paraspeckle as potential targets for managing hyperglycemia.
Project description:Type 2 Diabetes (T2D) is a global health issue characterized by abnormal blood glucose levels and often associated with excessive hepatic gluconeogenesis. Increased circulating non-essential amino acids (NEAAs) are consistently observed in T2D individuals; however, the specific contribution of each amino acid to T2D pathogenesis remains less understood. Here, we reported an unexpected role of the NEAA proline in coordinating hepatic glucose metabolism by modulating paraspeckle, a nuclear structure scaffolded by the long noncoding RNA Neat1. Mechanistically, proline diminished paraspeckles in hepatocytes, liberating the retained mRNA species into cytoplasm for translation, including the mRNAs of Ppargc1a and Foxo1, contributing to enhanced gluconeogenesis and hyperglycemia. We further demonstrated that the proline-paraspeckle-mRNA retention axis existed in diabetic liver samples, and intervening this axis via paraspeckle restoration significantly alleviated hyperglycemia in both female and male diabetic mouse models. Collectively, our results not only delineated a previously unappreciated proline-instigated, paraspeckle-dependent mRNA retention mechanism regulating gluconeogenesis, but also spotlighted proline and paraspeckle as potential targets for managing hyperglycemia.
Project description:Although thousands of long non-coding RNAs (lncRNAs) are localized in the nucleus, only a few dozen have been functionally characterized. We found that nuclear paraspeckle assembly transcript 1 (NEAT1), an essential lncRNA for the formation of nuclear body paraspeckles, is induced by poly I:C stimulation, resulting in excess formation of paraspeckles. Using microarray analysis, we investigated whether NEAT1 induction followed by excess formation of paraspeckles was involved in poly I:C-inducible gene expression.
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.
Project description:The goal of this study was to determine the identity of the RNA linked to the paraspeckles in the rat GH4C1 cell line. GH4C1 cell were fixed with 1% paraformaldehyde in PBS. Then nuclei were purified, lysed and sonicated. RNA pull-down was performed using two antisense DNA biotinylated oligonucleotide probes that target the lncRNA Neat1. Streptavidin-magnetic beads were added to hybridization reaction and complexes were captured by magnets. RNA was isolated using NucleoSpin®RNA XS (Macherey-Nagel).