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Pabis K, Barardo D, Sirbu O, Selvarajoo K, Gruber J, Kennedy BK. A concerted increase in readthrough and intron retention drives transposon expression during aging and senescence. eLife 2024; 12:RP87811. [PMID: 38567944 PMCID: PMC10990488 DOI: 10.7554/elife.87811] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2024] Open
Abstract
Aging and senescence are characterized by pervasive transcriptional dysfunction, including increased expression of transposons and introns. Our aim was to elucidate mechanisms behind this increased expression. Most transposons are found within genes and introns, with a large minority being close to genes. This raises the possibility that transcriptional readthrough and intron retention are responsible for age-related changes in transposon expression rather than expression of autonomous transposons. To test this, we compiled public RNA-seq datasets from aged human fibroblasts, replicative and drug-induced senescence in human cells, and RNA-seq from aging mice and senescent mouse cells. Indeed, our reanalysis revealed a correlation between transposons expression, intron retention, and transcriptional readthrough across samples and within samples. Both intron retention and readthrough increased with aging or cellular senescence and these transcriptional defects were more pronounced in human samples as compared to those of mice. In support of a causal connection between readthrough and transposon expression, analysis of models showing induced transcriptional readthrough confirmed that they also show elevated transposon expression. Taken together, our data suggest that elevated transposon reads during aging seen in various RNA-seq dataset are concomitant with multiple transcriptional defects. Intron retention and transcriptional readthrough are the most likely explanation for the expression of transposable elements that lack a functional promoter.
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Affiliation(s)
- Kamil Pabis
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of SingaporeSingaporeSingapore
- Healthy Longevity Translational Research Programme, Yong Loo Lin School of Medicine, National University of SingaporeSingaporeSingapore
- Centre for Healthy Longevity, National University Health SystemSingaporeSingapore
| | - Diogo Barardo
- Healthy Longevity Translational Research Programme, Yong Loo Lin School of Medicine, National University of SingaporeSingaporeSingapore
- Centre for Healthy Longevity, National University Health SystemSingaporeSingapore
| | - Olga Sirbu
- Bioinformatics Institute, Agency for Science, Technology and Research (A*STAR)SingaporeSingapore
| | - Kumar Selvarajoo
- Bioinformatics Institute, Agency for Science, Technology and Research (A*STAR)SingaporeSingapore
- Singapore Institute of Food and Biotechnology Innovation, Agency for Science, Technology and Research (A*STAR)SingaporeSingapore
- NUS Synthetic Biology for Clinical and Technological Innovation (SynCTI), National University of SingaporeSingaporeSingapore
- School of Biological Sciences, Nanyang Technological UniversitySingaporeSingapore
| | - Jan Gruber
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of SingaporeSingaporeSingapore
- Science Divisions, Yale-NUS CollegeSingaporeSingapore
| | - Brian K Kennedy
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of SingaporeSingaporeSingapore
- Healthy Longevity Translational Research Programme, Yong Loo Lin School of Medicine, National University of SingaporeSingaporeSingapore
- Centre for Healthy Longevity, National University Health SystemSingaporeSingapore
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Liang Y, Qu X, Shah NM, Wang T. Towards targeting transposable elements for cancer therapy. Nat Rev Cancer 2024; 24:123-140. [PMID: 38228901 DOI: 10.1038/s41568-023-00653-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 12/04/2023] [Indexed: 01/18/2024]
Abstract
Transposable elements (TEs) represent almost half of the human genome. Historically deemed 'junk DNA', recent technological advancements have stimulated a wave of research into the functional impact of TEs on gene-regulatory networks in evolution and development, as well as in diseases including cancer. The genetic and epigenetic evolution of cancer involves the exploitation of TEs, whereby TEs contribute directly to cancer-specific gene activities. This Review provides a perspective on the role of TEs in cancer as being a 'double-edged sword', both promoting cancer evolution and representing a vulnerability that could be exploited in cancer therapy. We discuss how TEs affect transcriptome regulation and other cellular processes in cancer. We highlight the potential of TEs as therapeutic targets for cancer. We also summarize technical hurdles in the characterization of TEs with genomic assays. Last, we outline open questions and exciting future research avenues.
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Affiliation(s)
- Yonghao Liang
- Department of Genetics, Washington University School of Medicine, Saint Louis, MO, USA
- Center for Genome Sciences and Systems Biology, Washington University School of Medicine, Saint Louis, MO, USA
| | - Xuan Qu
- Department of Genetics, Washington University School of Medicine, Saint Louis, MO, USA
- Center for Genome Sciences and Systems Biology, Washington University School of Medicine, Saint Louis, MO, USA
| | - Nakul M Shah
- Division of Cancer Medicine, University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Ting Wang
- Department of Genetics, Washington University School of Medicine, Saint Louis, MO, USA.
- Center for Genome Sciences and Systems Biology, Washington University School of Medicine, Saint Louis, MO, USA.
- McDonnell Genome Institute, Washington University School of Medicine, Saint Louis, MO, USA.
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Spirito G, Filosi M, Domenici E, Mangoni D, Gustincich S, Sanges R. Exploratory analysis of L1 retrotransposons expression in autism. Mol Autism 2023; 14:22. [PMID: 37381037 DOI: 10.1186/s13229-023-00554-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Accepted: 06/15/2023] [Indexed: 06/30/2023] Open
Abstract
BACKGROUND Autism spectrum disorder (ASD) is a set of highly heterogeneous neurodevelopmental diseases whose genetic etiology is not completely understood. Several investigations have relied on transcriptome analysis from peripheral tissues to dissect ASD into homogenous molecular phenotypes. Recently, analysis of changes in gene expression from postmortem brain tissues has identified sets of genes that are involved in pathways previously associated with ASD etiology. In addition to protein-coding transcripts, the human transcriptome is composed by a large set of non-coding RNAs and transposable elements (TEs). Advancements in sequencing technologies have proven that TEs can be transcribed in a regulated fashion, and their dysregulation might have a role in brain diseases. METHODS We exploited published datasets comprising RNA-seq data from (1) postmortem brain of ASD subjects, (2) in vitro cell cultures where ten different ASD-relevant genes were knocked out and (3) blood of discordant siblings. We measured the expression levels of evolutionarily young full-length transposable L1 elements and characterized the genomic location of deregulated L1s assessing their potential impact on the transcription of ASD-relevant genes. We analyzed every sample independently, avoiding to pool together the disease subjects to unmask the heterogeneity of the molecular phenotypes. RESULTS We detected a strong upregulation of intronic full-length L1s in a subset of postmortem brain samples and in in vitro differentiated neurons from iPSC knocked out for ATRX. L1 upregulation correlated with an high number of deregulated genes and retained introns. In the anterior cingulate cortex of one subject, a small number of significantly upregulated L1s overlapped with ASD-relevant genes that were significantly downregulated, suggesting the possible existence of a negative effect of L1 transcription on host transcripts. LIMITATIONS Our analyses must be considered exploratory and will need to be validated in bigger cohorts. The main limitation is given by the small sample size and by the lack of replicates for postmortem brain samples. Measuring the transcription of locus-specific TEs is complicated by the repetitive nature of their sequence, which reduces the accuracy in mapping sequencing reads to the correct genomic locus. CONCLUSIONS L1 upregulation in ASD appears to be limited to a subset of subjects that are also characterized by a general deregulation of the expression of canonical genes and an increase in intron retention. In some samples from the anterior cingulate cortex, L1s upregulation seems to directly impair the expression of some ASD-relevant genes by a still unknown mechanism. L1s upregulation may therefore identify a group of ASD subjects with common molecular features and helps stratifying individuals for novel strategies of therapeutic intervention.
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Affiliation(s)
- Giovanni Spirito
- Scuola Internazionale Superiore di Studi Avanzati (SISSA), Area of Neuroscience, Via Bonomea 265, 34136, Trieste, Italy
- Central RNA Laboratory, Istituto Italiano di Tecnologia - IIT, Via Enrico Melen 83, Building B, 16152, Genoa, Italy
- CMP3vda, Via Lavoratori Vittime del Col Du Mont 28, Aosta, Italy
| | - Michele Filosi
- Department of Cellular, Computational and Integrative Biology (CIBIO), University of Trento, Trento, TN, Italy
- Eurac Research, Institute for Biomedicine, Bolzano, BZ, Italy
| | - Enrico Domenici
- Department of Cellular, Computational and Integrative Biology (CIBIO), University of Trento, Trento, TN, Italy
- Fondazione The Microsoft Research - University of Trento Centre for Computational and Systems Biology (COSBI), Rovereto, TN, Italy
| | - Damiano Mangoni
- Central RNA Laboratory, Istituto Italiano di Tecnologia - IIT, Via Enrico Melen 83, Building B, 16152, Genoa, Italy
| | - Stefano Gustincich
- Central RNA Laboratory, Istituto Italiano di Tecnologia - IIT, Via Enrico Melen 83, Building B, 16152, Genoa, Italy.
- CMP3vda, Via Lavoratori Vittime del Col Du Mont 28, Aosta, Italy.
| | - Remo Sanges
- Scuola Internazionale Superiore di Studi Avanzati (SISSA), Area of Neuroscience, Via Bonomea 265, 34136, Trieste, Italy.
- Central RNA Laboratory, Istituto Italiano di Tecnologia - IIT, Via Enrico Melen 83, Building B, 16152, Genoa, Italy.
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Esposito M, Gualandi N, Spirito G, Ansaloni F, Gustincich S, Sanges R. Transposons Acting as Competitive Endogenous RNAs: In-Silico Evidence from Datasets Characterised by L1 Overexpression. Biomedicines 2022; 10:biomedicines10123279. [PMID: 36552034 PMCID: PMC9776036 DOI: 10.3390/biomedicines10123279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2022] [Revised: 12/07/2022] [Accepted: 12/11/2022] [Indexed: 12/23/2022] Open
Abstract
LINE L1 are transposable elements that can replicate within the genome by passing through RNA intermediates. The vast majority of these element copies in the human genome are inactive and just between 100 and 150 copies are still able to mobilize. During evolution, they could have been positively selected for beneficial cellular functions. Nonetheless, L1 deregulation can be detrimental to the cell, causing diseases such as cancer. The activity of miRNAs represents a fundamental mechanism for controlling transcript levels in somatic cells. These are a class of small non-coding RNAs that cause degradation or translational inhibition of their target transcripts. Beyond this, competitive endogenous RNAs (ceRNAs), mostly made by circular and non-coding RNAs, have been seen to compete for the binding of the same set of miRNAs targeting protein coding genes. In this study, we have investigated whether autonomously transcribed L1s may act as ceRNAs by analyzing public dataset in-silico. We observed that genes sharing miRNA target sites with L1 have a tendency to be upregulated when L1 are overexpressed, suggesting the possibility that L1 might act as ceRNAs. This finding will help in the interpretation of transcriptomic responses in contexts characterized by the specific activation of transposons.
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Affiliation(s)
- Mauro Esposito
- Computational Genomics Laboratory, Area of Neuroscience, Scuola Internazionale Superiore di Studi Avanzati (SISSA), 34136 Trieste, Italy
| | - Nicolò Gualandi
- Computational Genomics Laboratory, Area of Neuroscience, Scuola Internazionale Superiore di Studi Avanzati (SISSA), 34136 Trieste, Italy
| | - Giovanni Spirito
- Computational Genomics Laboratory, Area of Neuroscience, Scuola Internazionale Superiore di Studi Avanzati (SISSA), 34136 Trieste, Italy
- CMP3vda, via Lavoratori Vittime del Col Du Mont 28, 11100 Aosta, Italy
| | - Federico Ansaloni
- Computational Genomics Laboratory, Area of Neuroscience, Scuola Internazionale Superiore di Studi Avanzati (SISSA), 34136 Trieste, Italy
- Central RNA Laboratory, Istituto Italiano di Tecnologia, 16132 Genova, Italy
| | - Stefano Gustincich
- CMP3vda, via Lavoratori Vittime del Col Du Mont 28, 11100 Aosta, Italy
- Central RNA Laboratory, Istituto Italiano di Tecnologia, 16132 Genova, Italy
| | - Remo Sanges
- Computational Genomics Laboratory, Area of Neuroscience, Scuola Internazionale Superiore di Studi Avanzati (SISSA), 34136 Trieste, Italy
- Central RNA Laboratory, Istituto Italiano di Tecnologia, 16132 Genova, Italy
- Correspondence:
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Das S, Jones AE, Abrams JM. Generalized nuclear localization of retroelement transcripts. Mob DNA 2022; 13:30. [PMID: 36461093 PMCID: PMC9717504 DOI: 10.1186/s13100-022-00287-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Accepted: 11/19/2022] [Indexed: 12/03/2022] Open
Abstract
BACKGROUND LINE-1s, Alus and SVAs are the only retrotransposition competent elements in humans. Their mobilization followed by insertional mutagenesis is often linked to disease. Apart from these rare integration events, accumulation of retrotransposition intermediates in the cytoplasm is potentially pathogenic due to induction of inflammatory response pathways. Although the retrotransposition of LINE-1 and Alu retroelements has been studied in considerable detail, there are mixed observations about the localization of their RNAs. RESULTS We undertook a comprehensive and unbiased approach to analyze retroelement RNA localization using common cell lines and publicly available datasets containing RNA-sequencing data from subcellular fractions. Using our customized analytic pipeline, we compared localization patterns of RNAs transcribed from retroelements and single-copy protein coding genes. Our results demonstrate a generalized characteristic pattern of retroelement RNA nuclear localization that is conserved across retroelement classes as well as evolutionarily young and ancient elements. Preferential nuclear enrichment of retroelement transcripts was consistently observed in cell lines, in vivo and across species. Moreover, retroelement RNA localization patterns were dynamic and subject to change during development, as seen in zebrafish embryos. CONCLUSION The pronounced nuclear localization of transcripts arising from ancient as well as de novo transcribed retroelements suggests that these transcripts are retained in the nucleus as opposed to being re-imported to the nucleus or degraded in the cytoplasm. This raises the possibility that there is adaptive value associated with this localization pattern to the host, the retroelements or possibly both.
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Affiliation(s)
- Simanti Das
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Amanda E Jones
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - John M Abrams
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA.
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Ansaloni F, Gualandi N, Esposito M, Gustincich S, Sanges R. TEspeX: consensus-specific quantification of transposable element expression preventing biases from exonized fragments. Bioinformatics 2022; 38:4430-4433. [PMID: 35876845 PMCID: PMC9477521 DOI: 10.1093/bioinformatics/btac526] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 07/08/2022] [Accepted: 07/12/2022] [Indexed: 12/24/2022] Open
Abstract
SUMMARY Transposable elements (TEs) play key roles in crucial biological pathways. Therefore, several tools enabling the quantification of their expression were recently developed. However, many of the existing tools lack the capability to distinguish between the transcription of autonomously expressed TEs and TE fragments embedded in canonical coding/non-coding non-TE transcripts. Consequently, an apparent change in the expression of a given TE may simply reflect the variation in the expression of the transcripts containing TE-derived sequences. To overcome this issue, we have developed TEspeX, a pipeline for the quantification of TE expression at the consensus level. TEspeX uses Illumina RNA-seq short reads to quantify TE expression avoiding counting reads deriving from inactive TE fragments embedded in canonical transcripts. AVAILABILITY AND IMPLEMENTATION The tool is implemented in python3, distributed under the GNU General Public License (GPL) and available on Github at https://github.com/fansalon/TEspeX (Zenodo URL: https://doi.org/10.5281/zenodo.6800331). SUPPLEMENTARY INFORMATION Supplementary data are available at Bioinformatics online.
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Affiliation(s)
- Federico Ansaloni
- Area of Neuroscience, Scuola Internazionale Superiore di Studi Avanzati (SISSA), Trieste 34136, Italy,Central RNA Laboratory, Istituto Italiano di Tecnologia, Genova 16163, Italy
| | - Nicolò Gualandi
- Area of Neuroscience, Scuola Internazionale Superiore di Studi Avanzati (SISSA), Trieste 34136, Italy
| | - Mauro Esposito
- Area of Neuroscience, Scuola Internazionale Superiore di Studi Avanzati (SISSA), Trieste 34136, Italy
| | | | - Remo Sanges
- To whom correspondence should be addressed. or
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