Project description:Although numerous long noncoding RNAs (lncRNAs) have been identified, our understanding of their roles in mammalian physiology remains limited. Here we investigated the physiologic function of the conserved lncRNA Norad in vivo. Deletion of Norad in mice results in genomic instability and mitochondrial dysfunction, leading to a dramatic multi-system degenerative phenotype resembling premature aging. Loss of tissue homeostasis in Norad-deficient animals is attributable to augmented activity of PUMILIO proteins, which act as post-transcriptional repressors of target mRNAs to which they bind. Norad is the preferred RNA target of PUMILIO2 (PUM2) in mouse tissues and, upon loss of Norad, PUM2 hyperactively represses key genes required for mitosis and mitochondrial function. Accordingly, enforced Pum2 expression fully phenocopies Norad deletion, resulting in rapid-onset aging-associated phenotypes. These findings provide new insights and open new lines of investigation into the roles of noncoding RNAs and RNA binding proteins in normal physiology and aging.
Project description:Purpose: PUMILIO proteins are known to repress target genes by binding to PUMILIO response elements (PREs) in target mRNAs. The goal of this study was to demonstrate binding of endogenous PUM2 to the noncoding RNA NORAD and to identify PUM2 target genes in NORAD wild-type and knockout HCT116 cells. Methods: PAR-CLIP was performed with endogenous PUM2 in HCT116 cells and isogenic NORAD knockout cells. Results: Endogenous PUM2 binds to NORAD in HCT116 cells. In addition, PUM2 target genes were identified in HCT116 cells. Conclusions: PUM2 binds to NORAD through multiple PREs on NORAD. Compared to all other PUM2 target genes in HCT116, NORAD is the preferred binding partner of endogenous PUM2.
Project description:Although numerous long noncoding RNAs (lncRNAs) have been identified, our understanding of their roles in mammalian physiology remains limited. Here we investigated the physiologic function of the conserved lncRNA Norad in vivo. Deletion of Norad in mice results in genomic instability and mitochondrial dysfunction, leading to a dramatic multi-system degenerative phenotype resembling premature aging. Loss of tissue homeostasis in Norad-deficient animals is attributable to augmented activity of PUMILIO proteins, which act as post-transcriptional repressors of target mRNAs to which they bind. Norad is the preferred RNA target of PUMILIO2 (PUM2) in mouse tissues and, upon loss of Norad, PUM2 hyperactively represses key genes required for mitosis and mitochondrial function. Accordingly, enforced Pum2 expression fully phenocopies Norad deletion, resulting in rapid-onset aging-associated phenotypes. These findings provide new insights and open new lines of investigation into the roles of noncoding RNAs and RNA binding proteins in normal physiology and aging.
Project description:Although numerous long noncoding RNAs (lncRNAs) have been identified, our understanding of their roles in mammalian physiology remains limited. Here we investigated the physiologic function of the conserved lncRNA Norad in vivo. Deletion of Norad in mice results in genomic instability and mitochondrial dysfunction, leading to a dramatic multi-system degenerative phenotype resembling premature aging. Loss of tissue homeostasis in Norad-deficient animals is attributable to augmented activity of PUMILIO proteins, which act as post-transcriptional repressors of target mRNAs to which they bind. Norad is the preferred RNA target of PUMILIO2 (PUM2) in mouse tissues and, upon loss of Norad, PUM2 hyperactively represses key genes required for mitosis and mitochondrial function. Accordingly, enforced Pum2 expression fully phenocopies Norad deletion, resulting in rapid-onset aging-associated phenotypes. These findings provide new insights and open new lines of investigation into the roles of noncoding RNAs and RNA binding proteins in normal physiology and aging.
Project description:Purpose: PUMILIO proteins are known to repress target genes by specifically binding to PUMILIO response elements (PREs) in target mRNAs. NORAD is a noncoding RNA that negatively regulates PUMILIO activity. The goal of this study was to determine the gene expression changes that result from knockout of NORAD or overexpression of PUMILIO and to test whether NORAD knockout causes PUMILIO hyperactivity. Methods: RNA-seq libraries were prepared using the TruSeq Stranded Total RNA with Ribo-Zero Human/Mouse/Rat Sample Preparation kit (Illumina) and sequenced using the 100 bp paired-end protocol on an Illumina HiSeq 2000. For comparing NORAD+/+ and NORAD-/- HCT116 cells, 3 biological replicates per genotype were sequenced. For PUM overexpression experiments, 3 replicates of GFP-expressing HCT116 cells (negative control) and 2 independent PUM1- or PUM2-overexpressing clones (2 replicates each) were sequenced. Results: Gene expression profiles show that PUMILIO target genes are downregulated in both NORAD knockout cells and PUMILIO overexpressing cells. Conclusions: These data indicate that NORAD sequesters PUMILIO, preventing excessive repression of PUMILIO target genes that are important for maintaining genomic stability.
Project description:Thousands of long non-coding RNAs (lncRNAs) have been identified in the human genome, but specific biological functions and biochemical mechanisms have been discovered for only about a dozen lncRNAs. One specific lncRNA, Non-coding RNA Activated by DNA Damage (NORAD), has recently been shown by genetic deletion to be required for maintaining genomic stability, but its molecular mechanism is unknown. Here, we combine RNA antisense purification (RAP) and quantitative mass spectrometry to identify proteins that directly interact with NORAD in living cells. We show that NORAD interacts with proteins involved in DNA replication and repair in steady-state cells and localizes to the nucleus upon stimulation with replication stress or DNA damage. In particular, NORAD interacts with RBMX (an emerging component of the DNA-damage response) and encodes the strongest RBMX-binding site in the transcriptome. We demonstrate that NORAD controls the ability of RBMX to assemble a ribonucleoprotein complex, which we term NORAD-Activated Ribonucleoprotein Complex 1 (NARC1), containing known suppressors of genomic instability: topoisomerase I (TOP1), ALYREF and the PRPF19/CDC5L complex. Cells depleted of NORAD or RBMX display an increased frequency of chromosome segregation errors, reduced replication-fork velocity and altered cell cycle progression phenotypes that are mechanistically linked to TOP1 and PRPF19/CDC5L function. Expression of NORAD in trans can rescue defects caused by NORAD depletion, but rescue is significantly impaired when the RBMX-binding site in NORAD is deleted. Our results demonstrate that the interaction between NORAD and RBMX is important for NORAD function and that NORAD is required for the assembly of a previously unknown topoisomerase complex (NARC1) that contributes to maintaining genomic stability. Moreover, we uncover a novel function for lncRNAs in modulating the ability of an RNA-binding protein to assemble a higher-order ribonucleoprotein complex.
Project description:The presence of the PUF (Pumilio/FBF) domain defines a conserved family of RNA-binding proteins involved in repressing gene expression. It has been suggested that a conserved function of PUF proteins is to repress differentiation and sustain the mitotic proliferation of stem cells. In humans, Pumilio2 (PUM2) is expressed in embryonic stem cells and adult germ cells. To identify mRNAs associated with human PUM2 protein in adipose tissue stem cells (ADSC), we used a modified Ribonucleoprotein-ImmunoPrecipitation Microarray (RIP-Chip). PUM2 ribonucleoprotein (RNP) complexes were performed with 2 µg of anti-Pum2 antibody (goat polyclonal, Santa Cruz Biotechnology, CA, USA) bound to protein G-agarose beads (Sigma, Deisenhofen, Germany). ADSCs were lysed in polysome lysis buffer (Tris-HCl pH 7.4 15mM, MgCl2 15 mM, NaCl 0,3 M, 1% Triton X-100, 1 mM DTT, 100 U/ml RNase Out, PMSF 1mM and E64 10uM) for one hour at 4°C. Beads were washed, then buffer and cell lysate were added, and the reaction mixtures were tumbled for 2 hours at 4°C. After this incubation, the beads were thoroughly washed again with polysome lysis buffer and then either RNA extracted for microarray and RT-PCR experiments using the RNeasy mini kit (Qiagen). To control for non-specifically enriched RNAs, identical IPs were performed with beads precoated with preimmune goat serum as a negative control. RNA was processed for hybridization with GeneChip 3’ IVT Express (Affymetrix - Santa Clara, USA), according to the manufacturers instruction. Briefly, cDNA was synthesized from immunoprecipitated RNA using reverse transcriptase followed by second strand synthesis to generate double-stranded cDNA. An in vitro transcription reaction was used to generate biotinylated cRNA. After purification and fragmentation, cRNA was hybridized onto GeneChip Affymetrix Human Genome U133 Plus 2.0 arrays. Post hybridization washes were preformed on an Affymetrix GeneChip Fluidics Station 450. Arrays were scanned on an Affymetrix GeneChip Scanner 3000. Scanned arrays were normalized using GCRMA in Partek software (Partek Incorporated. St. Louis, MO). Differentially enriched RNAs were found after performing One-way ANOVA analysis comparing immunoprecipitated samples against control samples. Final lists of genes were obtained by filtering the data from the statistical results according to fold enrichment more than 2 and a p value associated of less than 0.05 for features with signal well above the background. Pum2 IP and control IP samples were analyzed for each of 2 biological replicates.
Project description:The number of known long noncoding RNA (lncRNA) functions is rapidly growing, but how those functions are encoded in their sequence and structure remains poorly understood. NORAD is a recently characterized, abundant, and highly conserved cytoplasmic lncRNA that is required for proper mitotic divisions in human cells. NORAD antagonizes repressors from the Pumilio family that bind at least 17 sites spread through 12 repetitive units in NORAD sequence. Here we study conserved sequences in NORAD repeats, identify additional interacting partners, and characterize the interaction between NORAD and the RNA binding protein SAM68 (KHDRBS1), which is required for NORAD function in antagonizing Pumilio. The interactions between NORAD, Pumilio and SAM68 provide a paradigm for how specific repeated and structured elements with a lncRNA can facilitate its function.