Long noncoding RNA as regulatory switch of protein turnover
Ontology highlight
ABSTRACT: Long intervening noncoding RNAs (lincRNAs) are prevalent genes with poorly understood functions. Here we discover a pathway of lincRNA-regulated proteolysis. The enhancer-like lincRNA HOTTIP extends the half-life of its binding protein WDR5, a subunit of the MLL H3K4 methylase complex, resulting in increased chromatin occupancy and gene activation. LincRNA-mediated stabilization requires direct RNA-protein interaction in a long RNA context, and blocks turnover at a step after target protein poly-ubiquitination. We elucidate the lincRNA binding interface on WDR5. A WDR5 mutant that selectively abrogates lincRNA binding becomes unstable, and is defective in gene activation, maintenance of histone H3 lysine 4 trimethylation, and embryonic stem cell self renewal. The ability to modulate protein turnover may allow lincRNAs to control the lifespan of molecular interactions at chromatin and elsewhere, broadening their scope in epigenetics and cell fate control. Gene expression analysis: To establish a differentiation signature for mouse V6.5 ES cells infected with anti mouse WDR5 shRNA, rescued with doxycycline inducible WDR5 WT or WDR5 F266A, total RNA was isolated in biologic duplicate from cells in different conditions and hybridized to Affymetrix Mouse 430 2.0 arrays.
Project description:Long intervening noncoding RNAs (lincRNAs) are prevalent genes with poorly understood functions. Here we discover a pathway of lincRNA-regulated proteolysis. The enhancer-like lincRNA HOTTIP extends the half-life of its binding protein WDR5, a subunit of the MLL H3K4 methylase complex, resulting in increased chromatin occupancy and gene activation. LincRNA-mediated stabilization requires direct RNA-protein interaction in a long RNA context, and blocks turnover at a step after target protein poly-ubiquitination. We elucidate the lincRNA binding interface on WDR5. A WDR5 mutant that selectively abrogates lincRNA binding becomes unstable, and is defective in gene activation, maintenance of histone H3 lysine 4 trimethylation, and embryonic stem cell self renewal. The ability to modulate protein turnover may allow lincRNAs to control the lifespan of molecular interactions at chromatin and elsewhere, broadening their scope in epigenetics and cell fate control.
Project description:There is growing recognition that mammalian cells produce many thousands of large intergenic transcripts. However, the functional significance of these transcripts has been particularly controversial. While there are some well-characterized examples, the vast majority (>95%) show little evidence of evolutionary conservation and have been suggested to represent transcriptional noise. Here, we report a new approach to identifying large non-coding RNAs (ncRNAs) by using chromatin-state maps to discover discrete transcriptional units intervening known protein-coding loci. Our approach identified ~1600 large multi-exonic RNAs across four mouse cell types. In sharp contrast to previous collections, these large intervening ncRNAs (lincRNAs) exhibit strong purifying selection in their genomic loci, exonic sequences, and promoter regions – with greater than 95% showing clear evolutionary conservation. We also developed a novel functional genomics approach that assigns putative functions to each lincRNA, revealing a diverse range of roles for lincRNAs in processes from ES pluripotency to cell proliferation. We obtained independent functional validation for the predictions for over 100 lincRNAs, using cell-based assays. In particular, we demonstrate that specific lincRNAs are transcriptionally regulated by key transcription factors in these processes such as p53, NFKB, Sox2, Oc4, and Nanog. Together, these results define a unique collection of functional lincRNAs that are highly conserved and implicated in diverse biological processes. lincRNA expression patterns were generated across a compendium of mouse tissues, cell types, and conditions. lincRNA expression profiles were generated on custom NimbleGen arrays (Samples GSM346609..GSM346650) and correlated with known protein coding genes on Affymetrix gene expression arrays (Samples GSM347910..GSM347943).
Project description:Large intergenic non-coding RNAs (lincRNAs) play widespread roles in epigenetic regulation during multiple differentiation processes, but little is known about their mode of action in cardiac differentiation. Here, we identified the key roles of a lincRNA, termed linc1405, in modulating the core network of cardiac differentiation by functionally interacting with Eomes. Chromatin- and RNA- immunoprecipitation assays showed that exon2 of linc1405 physically mediates a complex consisting of Eomes, Trithorax group (TrxG) subunit WDR5, and histone acetyltransferase GCN5 binding at the enhancer region of Mesp1 gene and activates its expression during cardiac mesoderm specification of embryonic stem cells. Importantly, linc1405 co-localizes with Eomes, WDR5, and GCN5 at the primitive streak and linc1405 depletion impairs heart development and function in vivo. In summary, linc1405 mediates a Eomes/WDR5/GCN5 complex that contributes to cardiogenesis, highlighting the critical roles of lincRNA-based complexes in the epigenetic regulation of cardiogenesis in vitro and in vivo.
Project description:There is growing recognition that mammalian cells produce many thousands of large intergenic transcripts. However, the functional significance of these transcripts has been particularly controversial. While there are some well-characterized examples, the vast majority (>95%) show little evidence of evolutionary conservation and have been suggested to represent transcriptional noise. Here, we report a new approach to identifying large non-coding RNAs (ncRNAs) by using chromatin-state maps to discover discrete transcriptional units intervening known protein-coding loci. Our approach identified ~1600 large multi-exonic RNAs across four mouse cell types. In sharp contrast to previous collections, these large intervening ncRNAs (lincRNAs) exhibit strong purifying selection in their genomic loci, exonic sequences, and promoter regions – with greater than 95% showing clear evolutionary conservation. We also developed a novel functional genomics approach that assigns putative functions to each lincRNA, revealing a diverse range of roles for lincRNAs in processes from ES pluripotency to cell proliferation. We obtained independent functional validation for the predictions for over 100 lincRNAs, using cell-based assays. In particular, we demonstrate that specific lincRNAs are transcriptionally regulated by key transcription factors in these processes such as p53, NFKB, Sox2, Oc4, and Nanog. Together, these results define a unique collection of functional lincRNAs that are highly conserved and implicated in diverse biological processes.
Project description:Thousands of large intervening non-coding RNAs (lincRNAs) have been identified in mammals. To better understand the evolution and functions of these enigmatic RNAs, we used chromatin marks, poly(A)-site mapping and RNA-Seq data, to identify more than 550 distinct lincRNAs in zebrafish. Although these shared many characteristics with mammalian lincRNAs, only 29 had detectable sequence similarity with putative mammalian orthologs, typically restricted to a single short region of high conservation. Other lincRNAs had conserved genomic locations without detectable sequence conservation. Antisense reagents targeting conserved regions of two zebrafish lincRNAs caused developmental defects. Reagents targeting splice sites caused the same defects and were rescued by adding either the mature lincRNA or its human or mouse ortholog. Our study provides a roadmap for identification and analysis of lincRNAs in model organisms and shows that lincRNAs play crucial biological roles during embryonic development with functionality conserved despite limited sequence conservation. H3K4me3, H3K36me3 chromatin maps, 3P-Seq and RNA-Seq were used to identify lincRNAs in the zebrafish genome
Project description:Thousands of large intervening non-coding RNAs (lincRNAs) have been identified in mammals. To better understand the evolution and functions of these enigmatic RNAs, we used chromatin marks, poly(A)-site mapping and RNA-Seq data, to identify more than 550 distinct lincRNAs in zebrafish. Although these shared many characteristics with mammalian lincRNAs, only 29 had detectable sequence similarity with putative mammalian orthologs, typically restricted to a single short region of high conservation. Other lincRNAs had conserved genomic locations without detectable sequence conservation. Antisense reagents targeting conserved regions of two zebrafish lincRNAs caused developmental defects. Reagents targeting splice sites caused the same defects and were rescued by adding either the mature lincRNA or its human or mouse ortholog. Our study provides a roadmap for identification and analysis of lincRNAs in model organisms and shows that lincRNAs play crucial biological roles during embryonic development with functionality conserved despite limited sequence conservation.
Project description:Numerous long intervening non-coding RNA (lincRNA) are generated from the mammalian genome by RNA polymerase II (Pol II) transcription. Although multiple functions have been ascribed to lincRNA, their synthesis and turnover remain poorly characterised. Here we define systematic differences in transcription and RNA processing between protein-coding and lincRNA genes in human HeLa cells. This is based on a range of nascent transcriptomic approaches applied to different nuclear fractions, including mammalian native elongating transcript sequencing (mNET-seq). Notably mNET-seq patterns specific for different Pol II CTD phosphorylation states reveal weak co-transcriptional splicing and poly(A) signal independent Pol II termination on lincRNA as compared to pre-mRNA. In addition, lincRNA are mostly restricted to chromatin where they are co-transcriptionally degraded by the RNA exosome. We also show that a lincRNA specific co-transcriptional RNA cleavage mechanism acts to induce premature termination. In effect functional lincRNA must escape from this targeted nuclear surveillance process.
Project description:Numerous studies over the past decade have elucidated a substantial set of long intergenic noncoding RNAs (lincRNAs). It has since become clear that lincRNAs constitute an important layer of genome regulation across a wide spectrum of species. Yet, the factors governing their evolution and origins remain relatively unexplored. One possible factor that may have shaped lincRNA biology are transposable elements (TEs). Here we set out to comprehensively characterize the TE content of lincRNAs relative to genomic averages and protein coding transcripts. Our analysis of the TE composition across 9241 human lincRNAs revealed that, in sharp contrast to protein coding genes, a striking majority (83%) of lincRNAs contain a TE, and TEs comprise 42% of lincRNA transcript sequences. LincRNA TE composition varies significantly from genomic averages, being depleted of LI and Alu elements and enriched for a broad class of endogenous retroviruses (ERVs). Furthermore, specific TE families occur in biased positions and orientations within lincRNAs, particularly at their transcription start sites, suggesting a role in the origin of those lincRNAs. Finally, we find that TEs can drive gene expression regulation of lincRNAs—we observed a dramatic correlation between lincRNAs containing HERVH elements and almost exclusive expression in pluripotent cells. Conversely, those lincRNAs that are devoid of TEs are more highly expressed in testis. Collectively, TEs pervade lincRNAs and have shaped lincRNA evolution and function via bestowing tissue-specific expression from donated transcriptional regulatory signals.
Project description:Numerous studies over the past decade have elucidated a substantial set of long intergenic noncoding RNAs (lincRNAs). It has since become clear that lincRNAs constitute an important layer of genome regulation across a wide spectrum of species. Yet, the factors governing their evolution and origins remain relatively unexplored. One possible factor that may have shaped lincRNA biology are transposable elements (TEs). Here we set out to comprehensively characterize the TE content of lincRNAs relative to genomic averages and protein coding transcripts. Our analysis of the TE composition across 9241 human lincRNAs revealed that, in sharp contrast to protein coding genes, a striking majority (83%) of lincRNAs contain a TE, and TEs comprise 42% of lincRNA transcript sequences. LincRNA TE composition varies significantly from genomic averages, being depleted of LI and Alu elements and enriched for a broad class of endogenous retroviruses (ERVs). Furthermore, specific TE families occur in biased positions and orientations within lincRNAs, particularly at their transcription start sites, suggesting a role in the origin of those lincRNAs. Finally, we find that TEs can drive gene expression regulation of lincRNAs—we observed a dramatic correlation between lincRNAs containing HERVH elements and almost exclusive expression in pluripotent cells. Conversely, those lincRNAs that are devoid of TEs are more highly expressed in testis. Collectively, TEs pervade lincRNAs and have shaped lincRNA evolution and function via bestowing tissue-specific expression from donated transcriptional regulatory signals. We extracted profiled the transcriptome expression polyadenylated mRNA-Seq. We then used these to reconstruct the transcriptome using de-novo assemblers and identify long non coding RNAs and their expression.