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 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:B2_Mm2 acts as a STAT1 binding site and interferon inducible enhancer of the nearbby interferon-stimulated gene Dicer1 during an innate immune response (IFNG stimulated). J774 knockouts deficient of B2_Mm2 were also found to have downregulated expression of Serpina3f and Serpina3g, indicating that B2_Mm2 acts as an enhancer on these nearby genes likely due to its capability as a CTCF-binding site.
Project description:B2_Mm2 acts as a STAT1 binding site and interferon inducible enhancer of the nearbby interferon-stimulated gene Dicer1 during an innate immune response (IFNG stimulated). J774 knockouts deficient of B2_Mm2 were also found to have downregulated expression of Serpina3f and Serpina3g, indicating that B2_Mm2 acts as an enhancer on these nearby genes likely due to its capability as a CTCF-binding site.
Project description:More than 97% of the mammalian genome is non-protein coding, and repetitive elements account for more than 50% of noncoding space. However, the functional importance of many non-coding RNAs generated by these elements and their connection with pathologic processes remains elusive. We have previously shown that B2 RNAs, a class of non-coding RNAs that belong to the B2 family of SINE repeats, mediate the transcriptional activation of stress response genes (SRGs) upon application of a stimulus. Notably, B2 RNAs bind RNA Polymerase II (RNA Pol II) and suppress SRG transcription during pro-stimulation state. Upon application of a stimulus, B2 RNAs are processed into fragments and degraded, which in turn releases RNA Pol II from suppression and upregulates SRGs. Here, we demonstrate a novel role for B2 RNAs in transcriptome response to amyloid beta toxicity and pathology in mouse hippocampus. In healthy hippocampi, activation of SRGs is followed by a transient upregulation of pro-apoptotic factors, such as p53 and miRNA-34c, which target SRGs creating a negative feedback loop that facilitates return to the pro-stimulation state. Using an integrative RNA genomics approach, we show that in mouse hippocampi with amyloid pathology and in an in vitro cell culture model of amyloid beta toxicity, this regulatory loop is dysfunctional due to increased levels of B2 RNA processing, constitutively elevated SRG expression and high p53 levels. Evidence indicates that Hsf1, a master regulator of stress response, mediates B2 RNA processing in cells, and is upregulated during amyloid toxicity accelerating the processing of SINE RNAs and SRG hyper-activation. This data attributes a role to SINE RNA processing in a pathological process as well as a new function to Hsf1 that is independent of its transcription factor activity. Our study reveals that in mouse, SINE RNAs constitute a novel pathway deregulated in amyloid beta pathology, with potential implications for similar cases in the human brain, such as Alzheimer’s disease (AD).
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:Six methyltransferases divide labor in establishing genomic profiles of histone H3 lysine 9 methylation (H3K9me), an epigenomic modification involved in the formation of constitutive heterochromatin, gene repression and silencing of retroelements. Among them, SETDB1 is recruited to active chromatin compartments to silence the expression of endogenous retroviruses. In the context of experiments aimed at determining the role of SETDB1 in stimulus-inducible gene expression in macrophages, we unexpectedly found that upon SETDB1 depletion, loss of H3K9me3 in active compartments was associated with increased recruitment of CTCF to >1,600 DNA-binding motifs contained within SINE-B2 repeats, a previously unidentified target of SETDB1-mediated repression. CTCF is an essential regulator of chromatin folding that restrains DNA looping by cohesin, thus creating boundaries among adjacent topological domains. Increased CTCF binding to SINE-B2 repeats generated novel boundaries within topological domains containing lipopolysaccharide-inducible genes, correlating with their impaired regulation in response to stimulation. These data indicate a role of H3K9me3 in restraining genomic distribution and activity of CTCF, with impact on chromatin organization and gene regulation.