Project description:The cellular accumulation of short non-coding RNAs (ncRNAs) transcribed by RNA Polymerase III (Pol III) is a hallmark of various cellular stressors and inflammatory-associated diseases. Yet, the mechanisms driving the accumulation of these RNAs are largely undefined. Infection with several DNA viruses is known to significantly alter the cellular Pol III transcriptome, leading to the induction of a class of non-coding retrotransposons known as short interspersed nuclear elements (SINE) and tRNA genes. Here, we sought to define the mechanisms driving Pol III transcribed ncRNA abundance during viral infection, using the murine herpesvirus MHV68 as a model. Our findings reveal that while the expression of Pol III transcripts, such as the murine-specific family of B2 SINE ncRNAs and pre-tRNAs, significantly increase during MHV68 infection, Pol III genomic occupancy is enhanced at a much fewer subset of B2 SINE and tRNA genes. Using DNA motif analyses and a convolutional neural network (CNN) based model, we identified non-promoter sequence elements within B2 SINE genes that distinguish infection-induced loci. We found that infection-induced B2 SINE genes are enriched for signal sequences that confer polyadenylation, and endogenous B2 SINE ncRNA polyadenylation depends on mRNA cleavage and polyadenylation (CPSF) machinery. We discovered that mRNA CPSF components are recruited to sites of Pol III transcription in response to MHV68 infection in a manner dependent on Pol III occupancy. Chromatin-associated B2 SINE ncRNAs are also bound by the CPSF complex, suggesting an RNA-dependent, co-transcriptional polyadenylation of B2 SINE ncRNAs. This uncovers an inducible, coupled relationship between Pol III transcription and mRNA-like polyadenylation of ncRNAs. Also, CPSF recruitment to Pol III genes is not restricted to murine genomes but also occurs at human SINE and tRNA genes, suggesting that this previously unknown coupled relationship may be a widespread feature of Pol III transcription.
Project description:We identified a novel long non-coding RNA Lx8-SINE B2, that is a marker of pluripotency. Depletion of Lx8-SINE B2 impacts embryonic stem cell self-renewal. RNA-seq analysis of Lx8-SINE B2 depletion revealed that a number of glycolytic genes with decreased expression. Mechanistically, we found that the Lx8-SINE B2 activates the glycolysis pathway by binding to Eno1. Collectively, our data suggest that Lx8-SINE B2 maintains the self-renewal of mESCs through glycolysis.
Project description:Short interspersed nuclear elements (SINEs) are retrotransposons evolutionarily derived from endogenous RNA Polymerase III RNAs. Though SINE elements have undergone exaptation into gene regulatory elements, how transcribed SINE RNA impacts transcriptional and post-transcriptional regulation is largely unknown. This is partly due to a lack of information regarding which of the loci have transcriptional potential. Here, we present an approach (short interspersed nuclear element sequencing, SINE-seq), which selectively profiles RNA Polymerase III-derived SINE RNA, thereby identifying transcriptionally active SINE loci. Applying SINE-seq to monitor murine B2 SINE expression during a gammaherpesvirus infection revealed transcription from 28,270 SINE loci, with ~50% of active SINE elements residing within annotated RNA Polymerase II loci. Furthermore, B2 RNA can form intermolecular RNA-RNA interactions with complementary mRNAs, leading to nuclear retention of the targeted mRNA via a mechanism involving p54nrb. These findings illuminate a pathway for the selective regulation of mRNA export during stress via retrotransposon activation.
Project description:We report the comparison between SINE B2-AS transcriptome profiling and Dicer1-deficient-cell transcriptome profiling using RNA-seq analysis. We report that thousands of SINE B2 copies encode long B2-AS transcripts, which are constantly degraded by Dicer1. This new class of B2-AS transcripts regulates the expression of SINE B2 sense (B2-S) transcripts. Long B2-S is the main cause of cellular toxicity likely mediated by the multifunctional protein TSPO. Some B2-AS transcripts are putative miRNAs interconnected with the RNAi system. We propose that B2-AS transcripts have evolved as a self-defense mechanism to subvert the host RNAi system.
Project description:Prior analysis suggsted that that AP-1 TFs play a role in expression of specific B2-SINE following in-vivo nerve injury. We thus sought to experimnetally test the role of AP-1 transcription factors in upregulation of B2-SINE RNA expression in DRG neurons. Neurons were transduced with PHP.S-AAV vectors expressing either A-Fos (dominant negative construct that targets Fos-interacting transcription factors), GFP control or were left untransduced. RNA was extracted 7 days later and analyzed to identify effects on B2-SINE expression and known AP-1 targetted mRNAs.
Project description:Alzheimer's disease (AD) is characterized by early molecular responses to amyloid beta neuro-toxicity that remain poorly defined. RNA editing by adenosine-to-inosine (A-to-I) conversion is a major epitranscriptomic mechanism, yet its contribution to non-coding RNA regulation during neurodegeneration is largely unknown. Short Interspersed Nuclear Element (SINE)-derived RNAs, including mouse B2 RNAs, represent the dominant substrates of A-to-I editing and have recently been shown to regulate gene expression through ribozyme-mediated processing. Here, we introduce and validate a repeat-aware bioinformatics framework that enables position-specific quantification of A-to-I editing within highly repetitive SINE RNAs - an analysis that has been challenging using standard genome-based pipelines. Applying this approach, we uncover discrete editing hotspots in B2 RNAs whose modification is selectively increased during the earliest stages of amyloid beta pathology. Elevated B2 RNA editing is consistently observed in hippocampal neurons exposed to acute amyloid beta toxicity. Functional perturbation of ADAR activity alters both B2 RNA editing levels and expression of B2 RNA-regulated stress response genes, directly linking RNA editing to SINE-mediated transcriptional control. Independent validation using Nanopore direct RNA sequencing supports increased RNA modification signals at the same B2 RNA regions identified by short-read Illumina sequencing. Together, our findings establish a previously unrecognized epitranscriptomic response to amyloid beta neurotoxicity mediated by site-specific A-to-I editing of SINE RNAs. This work defines a new analytical paradigm for studying RNA editing in RNAs from repetitive elements and reveals a regulatory axis connecting amyloid beta toxicity, ADAR activity, SINE RNA editing, and stress-responsive gene expression, with implications for conserved mechanisms underlying Alzheimer's disease and related neurodegenerative disorders.
Project description:More than one million copies of short interspersed elements (SINEs), a class of retrotransposons, are present in the mammalian genomes, particularly within gene-rich genomic regions. Evidence has accumulated that ancient SINE sequences have acquired new binding sites for transcription factors (TFs) through multiple mutations following retrotransposition, and as a result have rewired the host regulatory network during the course of evolution. However, it remains unclear whether currently active SINEs contribute to the expansion of TF binding sites. To study the mobility, expression, and function of SINE copies, we first identified about 2,000 insertional polymorphisms of B1 and B2 SINE families within Mus musculus. Using a novel RNA sequencing method developed here, we detected the expression of SINEs in testes at both the subfamily and genomic copy levels: the vast majority of B1 RNAs originated from evolutionarily young subfamilies, whereas B2 RNAs contained transcripts from both young and old subfamilies. DNA methylation and chromatin immunoprecipitation-sequencing (ChIP-seq) analyses revealed that polymorphic B2 insertions served as a chromatin boundary element inhibiting the expansion of DNA hypomethylated and histone hyperacetylated regions, and decreased the expression of neighboring genes. Moreover, a total of > 100 polymorphic B2 insertions were bound by CTCF, a well-known chromatin boundary protein. These results suggest that the currently active B2 copies are mobile chromatin boundary elements that can modulate gene expression level, and are likely involved in epigenomic and phenotypic diversification of the mouse species.