Project description:Enhancers determine spatiotemporal gene expression programs by engaging with long-range promoters. However, it remains unknown how enhancers find their cognate promoters. We recently developed a RIC-seq technology to identify enhancer-promoter connectivity using pairwise interacting enhancer RNAs and promoter-derived noncoding RNAs in HeLa cells. Here, we apply this technology to generate high-confidence enhancer-promoter RNA interaction (EPRI) maps in six additional cell lines. Using these maps, we discover that 37.9% of the enhancer-promoter RNA interaction sites are overlapped with Alu sequences. These pairwise interacting Alu and non-Alu RNA sequences tend to be complementary and potentially form duplexes. Knockout of Alu elements compromises enhancer-promoter looping, whereas Alu insertion or CRISPR-dCasRx-mediated Alu tethering to unregulated promoter RNAs can create new loops to homologous enhancers. Importantly, mapping 535,404 noncoding risk variants back to the EPRI maps enabled us to construct variant-to-function maps for interpreting their molecular functions, including 15,318 deletions or insertions in 11,677 Alu elements that affect 6,497 protein-coding genes. We further demonstrate that polymorphic Alu insertion at PTK2 enhancer can promote tumorigenesis. Our study uncovers a principle for determining enhancer-promoter pairing specificity and provides a framework to link noncoding risk variants to their molecular functions.
Project description:Alu elements are major contributors to lineage-specific new exons in primate and human genomes. Recent studies indicate that some Alu exons have high transcript inclusion levels or tissue-specific splicing profiles, and may play important regulatory roles in modulating mRNA degradation or translational efficiency. However, the contribution of Alu exons to the human proteome remains unclear and controversial. The prevailing view is that exons derived from young repetitive elements, such as Alu elements, are restricted to regulatory functions and have not had adequate evolutionary time to be incorporated into stable, functional proteins. We adopt a proteotranscriptomics approach to systematically assess the contribution of Alu exons to the human proteome. Using RNA sequencing, ribosome profiling and proteomics data from human tissues and cell lines, we provide evidence for the translational activities of Alu exons and the presence of Alu exon derived peptides in human proteins. These Alu exon peptides represent species-specific protein differences between primates and other mammals, and in certain instances between humans and closely related primates. In the case of the RNA editing enzyme ADARB1, which contains an Alu exon peptide in its catalytic domain, RNA sequencing analyses of A-to-I editing demonstrate that both the Alu exon skipping and inclusion isoforms encode active enzymes. The Alu exon derived peptide may fine tune the overall editing activity and, in limited cases, the site selectivity of ADARB1 protein products. Our data indicate that Alu elements have contributed to the acquisition of novel protein sequences during primate and human evolution.
Project description:Adenosine to Inosine (A-to-I) RNA editing is a site-specific modification of RNA transcripts, catalyzed by members of the ADAR (Adenosine Deaminase Acting on RNA) protein family. RNA editing occurs in human RNA in thousands of different sites. Some of the sites are located in protein-coding regions but the majority is found in non-coding regions, such as 3âUTRs, 5âUTRs and introns - mainly in Alu elements. While editing is found in all tissues, the highest levels of editing are found in the brain. It was shown that editing levels within protein-coding regions are increased during embryogenesis and after birth and that RNA editing is crucial for organism viability as well as for normal development. In this study we characterized the A-to-I RNA editing phenomenon during neuronal and spontaneous differentiation of human embryonic stem cells (hESCs). We identified high editing levels of Alu repetitive elements in hESCs and demonstrated a global decrease in editing levels of non-coding Alu sites when hESCs are differentiating, particularly into the neural lineage. Using RNA interference, we showed that the elevated editing levels of Alu elements in undifferentiated hESCs are highly dependent on ADAR1. DNA microarray analysis showed that ADAR1 knockdown has a global effect on gene expression in hESCs and leads to a significant increase in RNA expression levels of genes involved in differentiation and development processes, including neurogenesis. Taken together, our data suggest that A-to-I editing of Alu sequences plays a role in the regulation of hESC early differentiation decisions. Two samples, One control and the second treated
Project description:While liganded nuclear receptors are well established to regulate Pol II protein-coding transcription units, their role in regulation of DNA repeats remains largely unknown. Here, we report that ~2-3% of the ~1-200,000 human DR2 Alu repeats, particularly those in proximity to retinoic acid-activated Pol II transcription units, are bound and activated by retinoic acid receptor in human embryonic stem cells, triggering their Pol III-dependent transcription. The non-coding DR2 Alu transcripts are processed in a Dicer-dependent fashion into a series of small RNA products with sizes ranging ~28-65nt and exhibit substantial co-localization with P bodies. These small RNAs cause degradation of a subset of mRNAs critical for the "stem cell" state, which harbor complimentary sequences in their 3' untranslated regions. This regulation requires Ago3- dependent stabilization of full-length and processed DR2 Alu transcripts, and recruitment of Ago3-associated decapping complexes to the target mRNAs. Thus, the RAR/Pol III-dependent DR2 Alu transcriptional program in stem cells serves as a functional complement to the RAR/Pol II-dependent counterpart. ChIP-seq of H3K36me3 samples before and after RA (retinoic acid) treatments.
Project description:Adenosine to Inosine (A-to-I) RNA editing is a site-specific modification of RNA transcripts, catalyzed by members of the ADAR (Adenosine Deaminase Acting on RNA) protein family. RNA editing occurs in human RNA in thousands of different sites. Some of the sites are located in protein-coding regions but the majority is found in non-coding regions, such as 3’UTRs, 5’UTRs and introns - mainly in Alu elements. While editing is found in all tissues, the highest levels of editing are found in the brain. It was shown that editing levels within protein-coding regions are increased during embryogenesis and after birth and that RNA editing is crucial for organism viability as well as for normal development. In this study we characterized the A-to-I RNA editing phenomenon during neuronal and spontaneous differentiation of human embryonic stem cells (hESCs). We identified high editing levels of Alu repetitive elements in hESCs and demonstrated a global decrease in editing levels of non-coding Alu sites when hESCs are differentiating, particularly into the neural lineage. Using RNA interference, we showed that the elevated editing levels of Alu elements in undifferentiated hESCs are highly dependent on ADAR1. DNA microarray analysis showed that ADAR1 knockdown has a global effect on gene expression in hESCs and leads to a significant increase in RNA expression levels of genes involved in differentiation and development processes, including neurogenesis. Taken together, our data suggest that A-to-I editing of Alu sequences plays a role in the regulation of hESC early differentiation decisions.
Project description:An extrachromosomal replication system was established to examine the perturbation of Alu-carrying genes in response to elevated Alu RNAs in the opposite direction. The null hypothesis is that the Alu-carrying RNA duplex cannot trigger subsequent post-transcriptional regulation, manifesting a random perturbation of expression levels. Comparing HEK293 cells transfected and not-transfected with pDR2-Alu vectors.
Project description:While liganded nuclear receptors are well established to regulate Pol II protein-coding transcription units, their role in regulation of DNA repeats remains largely unknown. Here, we report that ~2-3% of the ~1-200,000 human DR2 Alu repeats, particularly those in proximity to retinoic acid-activated Pol II transcription units, are bound and activated by retinoic acid receptor in human embryonic stem cells, triggering their Pol III-dependent transcription. The non-coding DR2 Alu transcripts are processed in a Dicer-dependent fashion into a series of small RNA products with sizes ranging ~28-65nt and exhibit substantial co-localization with P bodies. These small RNAs cause degradation of a subset of mRNAs critical for the "stem cell" state, which harbor complimentary sequences in their 3' untranslated regions. This regulation requires Ago3- dependent stabilization of full-length and processed DR2 Alu transcripts, and recruitment of Ago3-associated decapping complexes to the target mRNAs. Thus, the RAR/Pol III-dependent DR2 Alu transcriptional program in stem cells serves as a functional complement to the RAR/Pol II-dependent counterpart.
Project description:Alu element is a major contributor to lineage-specific new exons in the primate and human genomes. Recent studies indicate that some Alu exons have high transcript inclusion levels or tissue-specific splicing profiles, and may play important regulatory roles in modulating mRNA degradation or translational efficiency. However, the contribution of Alu exons to the human proteome remains unclear and controversial. The prevailing view is that exons derived from young repetitive elements (such as Alu) are restricted to regulatory functions but do not have adequate evolutionary time to be incorporated into stable, functional proteins. In this work, we adopt a proteotranscriptomics approach to systematically assess the contribution of Alu exons to the human proteome. Using RNA sequencing, ribosome profiling, and mass spectrometry data of diverse human tissues and cell lines, we provide evidence for the translational activities of Alu exons and the presence of Alu exon derived peptides in human proteins. These Alu exon peptides represent species-specific protein differences between primates and other mammals, and in certain instances even between humans and closely related nonhuman primates. In the RNA editing enzyme ADARB1, which contains an Alu exon peptide in its catalytic domain, RNA editing analyses of RNA-sequencing data demonstrate that both the Alu exon skipping and inclusion isoforms encode active RNA editing enzymes, while the Alu exon peptide may fine tune the editing activities of the ADARB1 protein products . Together, our data indicate that Alu elements have contributed to the acquisition of novel protein sequences during primate and human evolution. Comparing the A-I RNA editing levels during HEK293 (control), ADARB1 long isoform (with Alu exon) transfected, and short isoform (without Alu exon) transfected cells, each group has 3 replicates.
Project description:This SuperSeries is composed of the following subset Series: GSE33149: Substrate selectivity for semisynthetic CK2 proteins with various posttranslational modifications GSE33150: Substrate selectivity for semisynthetic CK2 proteins with Pin1 Refer to individual Series
Project description:An extrachromosomal replication system was established to examine the perturbation of Alu-carrying genes in response to elevated Alu RNAs in the opposite direction. The null hypothesis is that the Alu-carrying RNA duplex cannot trigger subsequent post-transcriptional regulation, manifesting a random perturbation of expression levels.