Tranposable elements modulate human mRNAs and lncRNAs via specific RNA-protein interactions.
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ABSTRACT: Transposable elements (TEs) have significantly influenced the evolution of transcriptional regulatory networks in the human genome. Post-transcriptional regulation of human genes by TE-derived sequences has been observed in specific contexts, but has yet to be systematically and comprehensively investigated. Here, studied a collection of CLIP-Seq (CrossLinked ImmunoPrecipitation) experiments mapping the RNA binding sites for a diverse set of 46 human proteins across 68 experiments to explore the role of TEs in post-transcriptional regulation genome-wide via RNA-protein interactions. We detected widespread interactions between RNA binding proteins (RBPs) and various families of TE-derived sequence in the CLIP-Seq data. Alignment coverage clustered on specific positions of the TE consensus sequences, illuminating a diversity of TE-specific motifs for many RBPs. Evidence of binding and conservation of these motifs in the nonrepetitive transcriptome suggest that TEs have appropriated existing sequence preferences of the RBP. Upon depletion of the RBPs, transcripts possessing TE-derived binding sites were similarly regulated as those bound in nonrepetitive sequence. However, in a few cases the effect of RBP binding depended on the specific TE family boundM-bM-^@M-^Te.g., the ubiquitously expressed RBP HuR conferred opposite effects on stability to transcripts when bound to Alu elements versus other families. Our meta-analysis suggests a widespread role for TEs in shaping RNA-protein regulatory networks in the human genome. HuR formaldehyde RIP-Seq in K562 cells, with RIP and input sequenced in triplicate.
Project description:Transposable elements (TE) have been shown to contrain functional transcription factor (TF) binding sites for long, but the extent to which TEs contribute TF binding sites is not well know. Here, we comprehensively mapped binding sites for 26 pairs of orthologous TFs, in two pairs of human and mouse cell lines (i.e., leukemia, and lymphoblast), along with epigenomic profiles representing DNA methylation and six histone modifications. We found that on average, 20% of TF binding sites were embedded in TEs. We further identified 710 TF-TE relationships in which certain TE subfamilies enriched for TF binidng sites. TE-derived TF binding peaks were also strongly associated with decreased DNA methylation and increased enhancer-associated histone marks. Most of the TE-derived TF binding sites were species-specific, but we also identified conserved binding sites. Additionally, 66% of TE-derived TF binding events were cell-type specific, associated with cell-type specific epigenetic landscape. For data usage terms and conditions, please refer to http://www.genome.gov/27528022 and http://www.genome.gov/Pages/Research/ENCODE/ENCODEDataReleasePolicyFinal2008.pdf To evaluate the contribution of transposable elements (TE) to transcription factor (TF) binding landscapes, we profiled ChIP-seq datasets for 26 TFs in two cell lines in human and mouse, generated by the ENCODE and MouseENCODE consortia. The epigenomic profiles were evaluated from six histone modification in each of the cell lines, also generated by the consortia. We added DNA methylation to the epigenomic profiles, using two complementary techniques, MeDIP-seq and MRE-seq. The mouse data related to this study are available through GSE57230: http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE57230
Project description:Transposable elements (TE) have been shown to contrain functional transcription factor (TF) binding sites for long, but the extent to which TEs contribute TF binding sites is not well know. Here, we comprehensively mapped binding sites for 26 pairs of orthologous TFs, in two pairs of human and mouse cell lines (i.e., leukemia, and lymphoblast), along with epigenomic profiles representing DNA methylation and six histone modifications. We found that on average, 20% of TF binding sites were embedded in TEs. We further identified 710 TF-TE relationships in which certain TE subfamilies enriched for TF binidng sites. TE-derived TF binding peaks were also strongly associated with decreased DNA methylation and increased enhancer-associated histone marks. Most of the TE-derived TF binding sites were species-specific, but we also identified conserved binding sites. Additionally, 66% of TE-derived TF binding events were cell-type specific, associated with cell-type specific epigenetic landscape. For data usage terms and conditions, please refer to http://www.genome.gov/27528022 and http://www.genome.gov/Pages/Research/ENCODE/ENCODEDataReleasePolicyFinal2008.pdf To evaluate the contribution of transposable elements (TE) to transcription factor (TF) binding landscapes, we profiled ChIP-seq datasets for 26 TFs in two cell lines in human and mouse, generated by the ENCODE and MouseENCODE consortia. The epigenomic profiles were evaluated from six histone modification in each of the cell lines, also generated by the consortia. We added DNA methylation to the epigenomic profiles, using two complementary techniques, MeDIP-seq and MRE-seq. The human data related to this study are available through GSE56774: http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE56774
Project description:Transposable elements (TEs) are often the primary determinant of genome size differences among eukaryotes. In plants, the proliferation of TEs is countered through epigenetic silencing mechanisms that prevent transposition. Recent studies using the model plant Arabidopsis thaliana have revealed that methylated TE insertions are often associated with reduced expression of nearby genes, and these insertions may be subject to purifying selection due to their effect on nearby genes. Less is known about the genome-wide patterns of epigenetic silencing of TEs in other plant species. Here, we compare the 24-nt siRNA complement from Arabidopsis thaliana and a closely related congener with a two- to three-fold higher TE copy number, A. lyrata. We show that TEs, and particularly siRNA-targeted TEs, are associated with reduced gene expression within both species and also with gene expression differences between orthologs. In addition, A. lyrata TEs are targeted by a lower fraction of uniquely matching siRNAs, which are associated with more effective silencing of TE expression. Overall, our results suggest that the efficacy of RNA-directed DNA methylation silencing is lower in A. lyrata, a finding that may shed light on the causes of differential TE proliferation among species. 4 A. lyrata mRNA-seq samples
Project description:Protein binding is essential to the transport, decay and regulation of almost all RNA molecules. However, the structural preference of protein binding on RNAs and their cellelar functions and dynamics upon changing environmental condictions are poorly understood. Here, we integrated various high-throughput data and introduced a computational framework to describe the global interactions between RNA binding proteins (RBPs) and structured RNAs in yeast at single-nucleotide resolution. We found that on average, in terms of percent total lengths, ~15% of mRNA untranslated regions (UTRs), ~37% of canonical ncRNAs and ~11% of long ncRNA (lncRNAs) are bound by proteins. The RBP binding sites, in general, tend to occur at single-stranded loops, with evolutionarily conserved signatures, and often facilitate a specific RNA structure conformation in vivo. We found that four nucleotide modifications of tRNA are significantly associated with RBP binding. We also identified various structural motifs bound by RBPs in the UTRs of mRNAs, associated with localization, degradation and stress responces. Moreover, we identified >200 novel lncRNAs bound by RBPs, and about half of them contain conserved secondary structures. We present the first ensemble pattern of RBP binding sites in the structured noncoding regions of a eukaryotic genome, emphasizing their structural context and cellular functions. Duplicate gPAR-CLIP libraries were sequenced from yeast strains for each of three conditions: log-phase growth, growth after 2 hour glucose starvation, and growth after 2 hour nitrogen starvation. polyA RNAs were isolated for all conditions. Total RNA were isolated from log phase growth conditions. Sucrose gradient fractionation was performed: some RNAs were isolated from the "light" fraction (lighter than 40S ribosome) and some from the "heavy" fraction. gPAR-CLIP libraries were used to determine regions of RNA bound by proteins.
Project description:Transposable elements (TEs) have significantly influenced the evolution of transcriptional regulatory networks in the human genome. Post-transcriptional regulation of human genes by TE-derived sequences has been observed in specific contexts, but has yet to be systematically and comprehensively investigated. Here, studied a collection of CLIP-Seq (CrossLinked ImmunoPrecipitation) experiments mapping the RNA binding sites for a diverse set of 46 human proteins across 68 experiments to explore the role of TEs in post-transcriptional regulation genome-wide via RNA-protein interactions. We detected widespread interactions between RNA binding proteins (RBPs) and various families of TE-derived sequence in the CLIP-Seq data. Alignment coverage clustered on specific positions of the TE consensus sequences, illuminating a diversity of TE-specific motifs for many RBPs. Evidence of binding and conservation of these motifs in the nonrepetitive transcriptome suggest that TEs have appropriated existing sequence preferences of the RBP. Upon depletion of the RBPs, transcripts possessing TE-derived binding sites were similarly regulated as those bound in nonrepetitive sequence. However, in a few cases the effect of RBP binding depended on the specific TE family bound—e.g., the ubiquitously expressed RBP HuR conferred opposite effects on stability to transcripts when bound to Alu elements versus other families. Our meta-analysis suggests a widespread role for TEs in shaping RNA-protein regulatory networks in the human genome.
Project description:Protein-RNA interactions are integral components of nearly every aspect of biology including regulation of gene expression, assembly of cellular architectures, and pathogenesis of human diseases. However, studies in the past few decades have only uncovered a small fraction of the vast landscape of the protein-RNA interactome in any organism, and even less is known about the dynamics of protein-RNA interactions under changing developmental and environmental conditions. Here, we describe the gPAR-CLIP (global photoactivatable-ribonucleoside-enhanced crosslinking and immunopurification) approach for capturing regions of the transcriptome bound by RNA-binding proteins (RBPs) in budding yeast. We report over 13,000 RBP crosslinking sites in untranslated regions (UTR) covering 72% of protein-coding transcripts encoded in the genome, confirming 3M-bM-^@M-^Y UTRs as major sites for RBP interaction. Comparative genomic analyses reveal that RBP crosslinking sites are highly conserved, and RNA folding predictions indicate that secondary structural elements are constrained by protein binding and may serve as generalizable modes of RNA recognition. Finally, 38% of 3M-bM-^@M-^Y UTR crosslinking sites show changes in RBP occupancy upon glucose or nitrogen deprivation, with major impacts on metabolic pathways as well as mitochondrial and ribosomal gene expression. Our study offers an unprecedented view of the pervasiveness and dynamics of protein-RNA interactions in vivo. Duplicate gPAR-CLIP and mRNA-seq libraries were sequenced from yeast strains for each of three conditions: log-phase growth, growth after 2 hour glucose starvation, and growth after 2 hour nitrogen starvation. Additional duplicate mRNA-seq libraries were sequenced from yeast strains grown in the absence of 4-thiouracil. gPAR-CLIP libraries were used to determine regions of mRNA bound by proteins. mRNA-seq libraries served as controls for mRNA abundance. A Puf3p PAR-CLIP library was sequenced to determine how well gPAR-CLIP captured the binding signatures of a single RNA-binding protein.
Project description:Transposable elements (TEs) are threats to genome stability and thus small RNA-mediated heterochromatinization suppresses the transcription of TEs. Paradoxically, transcription of non-coding RNA (ncRNA) from TEs is needed for the production of TE-targeting small RNAs and/or recruiting the silencing machinery to TEs. Hence, specialized RNA polymerase II (Pol II) transcription machinery is required for such unconventional transcription in different organisms. Indeed, the developmental stage-specific Mediator complex (Med)-associated proteins play essential roles in the ncRNA transcription from TE-related sequences in Tetrahymena. Yet it remains unknown how those Med-associated proteins are linked to the TE transcription by Pol II. Here, have found that Pol II is regulated by Emit3, a stage-specific, TFIIB-like protein specialized in TE transcription. Hence, to find out potential interactions, we did LC-MS/MS analysis for immunoprecipitation samples of Emit3 and the zinc-ribbon mutated Emit3.
Project description:RNA-directed DNA methylation (RdDM) is a transcriptional silencing mechanism mediated by small and long noncoding RNAs produced by the plant-specific RNA polymerases Pol IV and Pol V, respectively. Through a chemical genetics screen with a luciferase-based DNA methylation reporter, LUCL, we found that camptothecin, a compound with anti-cancer properties that targets DNA topoisomerase 1a (TOP1a) was able to de-repress LUCL by reducing its DNA methylation and H3K9 dimethylation (H3K9me2) levels. Further studies with Arabidopsis top1a mutants showed that TOP1a promotes RdDM by facilitating the production of Pol V-dependent long non-coding RNAs, AGONAUTE4 recruitment and H3K9me2 deposition at transposable elements (TEs). 5 small RNA libraries were sequenced
Project description:Imprinted gene expression occurs during seed development in plants and is associated with differential DNA methylation of parental alleles, particularly at proximal transposable elements (TEs). Imprinting variability could contribute to observed parent-of-origin effects on seed development. We investigated intraspecific variation in imprinting, coupled with analysis of DNA methylation and small RNAs, among three Arabidopsis strains with diverse seed phenotypes. The majority of imprinted genes were parentally biased in the same manner among all strains. However, we identified several examples of allele-specific imprinting correlated with intraspecific epigenetic variation at a TE. We successfully predicted imprinting in additional strains based on methylation variability. We conclude that there is standing variation in imprinting even in recently diverged genotypes due to intraspecific epiallelic variation. These data demonstrate that epiallelic variation and genomic imprinting intersect to produce novel gene expression patterns in seeds. Whole genome bisulfite sequencing of embryo and endosperm (14 samples).
Project description:East African cichlid fishes have radiated in an explosive fashion. The (epi)genetic basis for the abundant phenotypic diversity of these fishes remains largely unknown. As transposable elements (TEs) contribute extensively to genome evolution, we reasoned that TEs may have fuelled cichlid radiations. While TE-derived genetic and epigenetic variability has been associated with phenotypic traits, TE expression and epigenetic silencing remain unexplored in cichlids. Here, we profiled TE expression in African cichlids, and describe dynamic expression patterns during embryogenesis and according to sex. Most TE silencing factors are conserved and expressed in cichlids. We describe an expansion of two truncated Piwil1 genes in Lake Malawi/Nyasa cichlids, encoding a Piwi domain with catalytic potential. To further dissect epigenetic silencing of TEs, we focused on small RNA-driven epigenetic silencing. We detect a small RNA population in gonads consistent with an active Piwi-interacting RNA (piRNA) pathway targeting TEs. We uncover fluid genomic origins of piRNAs in closely related cichlid species. This, along with signatures of positive selection in piRNA pathway factors, points towards fast co-evolution of TEs and the piRNA pathway. Our study is the first step to understand the contribution of ongoing TE-host arms races to the cichlid radiations in Africa.