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Bravo JI, Zhang L, Benayoun BA. Multi-ancestry GWAS reveals loci linked to human variation in LINE-1- and Alu-copy numbers. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.09.10.612283. [PMID: 39314493 PMCID: PMC11419044 DOI: 10.1101/2024.09.10.612283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 09/25/2024]
Abstract
Long INterspersed Element-1 (LINE-1; L1) and Alu are two families of transposable elements (TEs) occupying ~17% and ~11% of the human genome, respectively. Though only a small fraction of L1 copies is able to produce the machinery to mobilize autonomously, Alu elements and degenerate L1 copies can hijack their functional machinery and mobilize in trans. The expression and subsequent copy number expansion of L1 and Alu can exert pathological effects on their hosts, promoting genome instability, inflammation, and cell cycle alterations. These features have made L1 and Alu promising focus subjects in studies of aging and aging diseases where they can become active. However, the mechanisms regulating variation in their expression and copy number remain incompletely characterized. Moreover, the relevance of known mechanisms to diverse human populations remains unclear, as mechanisms are often characterized in isogenic cell culture models. To address these gaps, we leveraged genomic data from the 1000 Genomes Project to carry out a trans-ethnic GWAS of L1 and Alu insertion global singletons. These singletons are rare insertions observed only once in a population, potentially reflecting recently acquired L1 and Alu integrants or structural variants, and which we used as proxies for L1/Alu-associated copy number variation. Our computational approach identified single nucleotide variants in genomic regions containing genes with potential and known TE regulatory properties, and it enriched for single nucleotide variants in regions containing known regulators of L1 expression. Moreover, we identified many reference TE copies and polymorphic structural variants that were associated with L1/Alu singletons, suggesting their potential contribution to TE copy number variation through transposition-dependent or transposition-independent mechanisms. Finally, a transcriptional analysis of lymphoblastoid cells highlighted potential cell cycle alterations in a subset of samples harboring L1/Alu singletons. Collectively, our results (i) suggest that known TE regulatory mechanisms may also play regulatory roles in diverse human populations, (ii) expand the list of genic and repetitive genomic loci implicated in TE copy number variation, and (iii) reinforce the links between TEs and disease.
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Affiliation(s)
- Juan I. Bravo
- Leonard Davis School of Gerontology, University of Southern California, Los Angeles, CA 90089, USA
| | - Lucia Zhang
- Leonard Davis School of Gerontology, University of Southern California, Los Angeles, CA 90089, USA
- Quantitative and Computational Biology Department, USC Dornsife College of Letters, Arts and Sciences, Los Angeles, California, USA
| | - Bérénice A. Benayoun
- Leonard Davis School of Gerontology, University of Southern California, Los Angeles, CA 90089, USA
- Molecular and Computational Biology Department, USC Dornsife College of Letters, Arts and Sciences, Los Angeles, CA 90089, USA
- Biochemistry and Molecular Medicine Department, USC Keck School of Medicine, Los Angeles, CA 90089, USA
- USC Norris Comprehensive Cancer Center, Epigenetics and Gene Regulation, Los Angeles, CA 90089, USA
- USC Stem Cell Initiative, Los Angeles, CA 90089, USA
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Wang ZY, Ge LP, Ouyang Y, Jin X, Jiang YZ. Targeting transposable elements in cancer: developments and opportunities. Biochim Biophys Acta Rev Cancer 2024; 1879:189143. [PMID: 38936517 DOI: 10.1016/j.bbcan.2024.189143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Revised: 05/23/2024] [Accepted: 06/19/2024] [Indexed: 06/29/2024]
Abstract
Transposable elements (TEs), comprising nearly 50% of the human genome, have transitioned from being perceived as "genomic junk" to key players in cancer progression. Contemporary research links TE regulatory disruptions with cancer development, underscoring their therapeutic potential. Advances in long-read sequencing, computational analytics, single-cell sequencing, proteomics, and CRISPR-Cas9 technologies have enriched our understanding of TEs' clinical implications, notably their impact on genome architecture, gene regulation, and evolutionary processes. In cancer, TEs, including long interspersed element-1 (LINE-1), Alus, and long terminal repeat (LTR) elements, demonstrate altered patterns, influencing both tumorigenic and tumor-suppressive mechanisms. TE-derived nucleic acids and tumor antigens play critical roles in tumor immunity, bridging innate and adaptive responses. Given their central role in oncology, TE-targeted therapies, particularly through reverse transcriptase inhibitors and epigenetic modulators, represent a novel avenue in cancer treatment. Combining these TE-focused strategies with existing chemotherapy or immunotherapy regimens could enhance efficacy and offer a new dimension in cancer treatment. This review delves into recent TE detection advancements, explores their multifaceted roles in tumorigenesis and immune regulation, discusses emerging diagnostic and therapeutic approaches centered on TEs, and anticipates future directions in cancer research.
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Affiliation(s)
- Zi-Yu Wang
- Department of Breast Surgery, Fudan University Shanghai Cancer Center; Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China
| | - Li-Ping Ge
- Department of Breast Surgery, Fudan University Shanghai Cancer Center; Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China
| | - Yang Ouyang
- Department of Breast Surgery, Fudan University Shanghai Cancer Center; Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China
| | - Xi Jin
- Department of Breast Surgery, Fudan University Shanghai Cancer Center; Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China
| | - Yi-Zhou Jiang
- Department of Breast Surgery, Fudan University Shanghai Cancer Center; Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China.
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Rodríguez TC, Yurkovetskiy L, Nagalekshmi K, Lam CHO, Jazbec E, Maitland SA, Wolfe SA, Sontheimer EJ, Luban J. PRC1.6 localizes on chromatin with the human silencing hub (HUSH) complex for promoter-specific silencing. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.07.12.603173. [PMID: 39026796 PMCID: PMC11257501 DOI: 10.1101/2024.07.12.603173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/20/2024]
Abstract
An obligate step in the life cycle of HIV-1 and other retroviruses is the establishment of the provirus in target cell chromosomes. Transcriptional regulation of proviruses is complex, and understanding the mechanisms underlying this regulation has ramifications for fundamental biology, human health, and gene therapy implementation. The three core components of the Human Silencing Hub (HUSH) complex, TASOR, MPHOSPH8 (MPP8), and PPHLN1 (Periphilin 1), were identified in forward genetic screens for host genes that repress provirus expression. Subsequent loss-of-function screens revealed accessory proteins that collaborate with the HUSH complex to silence proviruses in particular contexts. To identify proteins associated with a HUSH complex-repressed provirus in human cells, we developed a technique, Provirus Proximal Proteomics, based on proximity labeling with C-BERST (dCas9-APEX2 biotinylation at genomic elements by restricted spatial tagging). Our screen exploited a lentiviral reporter that is silenced by the HUSH complex in a manner that is independent of the integration site in chromatin. Our data reveal that proviruses silenced by the HUSH complex are associated with DNA repair, mRNA processing, and transcriptional silencing proteins, including L3MBTL2, a member of the non-canonical polycomb repressive complex 1.6 (PRC1.6). A forward genetic screen confirmed that PRC1.6 components L3MBTL2 and MGA contribute to HUSH complex-mediated silencing. PRC1.6 was then shown to silence HUSH-sensitive proviruses in a promoter-specific manner. Genome wide profiling showed striking colocalization of the PRC1.6 and HUSH complexes on chromatin, primarily at sites of active promoters. Finally, PRC1.6 binding at a subset of genes that are silenced by the HUSH complex was dependent on the core HUSH complex component MPP8. These studies offer new tools with great potential for studying the transcriptional regulation of proviruses and reveal crosstalk between the HUSH complex and PRC1.6.
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Affiliation(s)
- Tomás C. Rodríguez
- RNA Therapeutics Institute, University of Massachusetts Chan Medical School, Worcester, MA, 01605, USA
| | - Leonid Yurkovetskiy
- Program in Molecular Medicine, University of Massachusetts Chan Medical School, Worcester, MA, 01605, USA
| | - Karthika Nagalekshmi
- Program in Molecular Medicine, University of Massachusetts Chan Medical School, Worcester, MA, 01605, USA
| | - Chin Hung Oscar Lam
- Graduate School of Biomedical Sciences, University of Massachusetts Chan Medical School, Worcester, MA, 01605, USA
| | - Eva Jazbec
- Graduate School of Biomedical Sciences, University of Massachusetts Chan Medical School, Worcester, MA, 01605, USA
| | - Stacy A. Maitland
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Scot A. Wolfe
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, Worcester, MA, USA
- Li Weibo Institute for Rare Diseases Research, University of Massachusetts Chan Medical School, Worcester, MA, 01605, USA
- Department of Biochemistry and Molecular Biotechnology, University of Massachusetts Chan Medical School, Worcester, MA, 01605, USA
| | - Erik J. Sontheimer
- RNA Therapeutics Institute, University of Massachusetts Chan Medical School, Worcester, MA, 01605, USA
- Program in Molecular Medicine, University of Massachusetts Chan Medical School, Worcester, MA, 01605, USA
- Li Weibo Institute for Rare Diseases Research, University of Massachusetts Chan Medical School, Worcester, MA, 01605, USA
- Department of Biochemistry and Molecular Biotechnology, University of Massachusetts Chan Medical School, Worcester, MA, 01605, USA
| | - Jeremy Luban
- RNA Therapeutics Institute, University of Massachusetts Chan Medical School, Worcester, MA, 01605, USA
- Program in Molecular Medicine, University of Massachusetts Chan Medical School, Worcester, MA, 01605, USA
- Li Weibo Institute for Rare Diseases Research, University of Massachusetts Chan Medical School, Worcester, MA, 01605, USA
- Department of Biochemistry and Molecular Biotechnology, University of Massachusetts Chan Medical School, Worcester, MA, 01605, USA
- Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
- Ragon Institute of MGH, MIT, and Harvard, Cambridge, MA 02139, USA
- Massachusetts Consortium on Pathogen Readiness, Boston, MA 02115, USA
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Bravo JI, Mizrahi CR, Kim S, Zhang L, Suh Y, Benayoun BA. An eQTL-based approach reveals candidate regulators of LINE-1 RNA levels in lymphoblastoid cells. PLoS Genet 2024; 20:e1011311. [PMID: 38848448 PMCID: PMC11189215 DOI: 10.1371/journal.pgen.1011311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2023] [Revised: 06/20/2024] [Accepted: 05/21/2024] [Indexed: 06/09/2024] Open
Abstract
Long interspersed element 1 (LINE-1; L1) are a family of transposons that occupy ~17% of the human genome. Though a small number of L1 copies remain capable of autonomous transposition, the overwhelming majority of copies are degenerate and immobile. Nevertheless, both mobile and immobile L1s can exert pleiotropic effects (promoting genome instability, inflammation, or cellular senescence) on their hosts, and L1's contributions to aging and aging diseases is an area of active research. However, because of the cell type-specific nature of transposon control, the catalogue of L1 regulators remains incomplete. Here, we employ an eQTL approach leveraging transcriptomic and genomic data from the GEUVADIS and 1000Genomes projects to computationally identify new candidate regulators of L1 RNA levels in lymphoblastoid cell lines. To cement the role of candidate genes in L1 regulation, we experimentally modulate the levels of top candidates in vitro, including IL16, STARD5, HSD17B12, and RNF5, and assess changes in TE family expression by Gene Set Enrichment Analysis (GSEA). Remarkably, we observe subtle but widespread upregulation of TE family expression following IL16 and STARD5 overexpression. Moreover, a short-term 24-hour exposure to recombinant human IL16 was sufficient to transiently induce subtle, but widespread, upregulation of L1 subfamilies. Finally, we find that many L1 expression-associated genetic variants are co-associated with aging traits across genome-wide association study databases. Our results expand the catalogue of genes implicated in L1 RNA control and further suggest that L1-derived RNA contributes to aging processes. Given the ever-increasing availability of paired genomic and transcriptomic data, we anticipate this new approach to be a starting point for more comprehensive computational scans for regulators of transposon RNA levels.
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Affiliation(s)
- Juan I. Bravo
- Leonard Davis School of Gerontology, University of Southern California, Los Angeles, California, United States of America
- Graduate program in the Biology of Aging, University of Southern California, Los Angeles, California, United States of America
| | - Chanelle R. Mizrahi
- Leonard Davis School of Gerontology, University of Southern California, Los Angeles, California, United States of America
- USC Gerontology Enriching MSTEM to Enhance Diversity in Aging Program, University of Southern California, Los Angeles, California, United States of America
| | - Seungsoo Kim
- Department of Obstetrics and Gynecology, Columbia University Irving Medical Center, New York, New York, United States of America
| | - Lucia Zhang
- Leonard Davis School of Gerontology, University of Southern California, Los Angeles, California, United States of America
- Quantitative and Computational Biology Department, USC Dornsife College of Letters, Arts and Sciences, Los Angeles, California, United States of America
| | - Yousin Suh
- Department of Obstetrics and Gynecology, Columbia University Irving Medical Center, New York, New York, United States of America
- Department of Genetics and Development, Columbia University Irving Medical Center, New York, New York, United States of America
| | - Bérénice A. Benayoun
- Leonard Davis School of Gerontology, University of Southern California, Los Angeles, California, United States of America
- Molecular and Computational Biology Department, USC Dornsife College of Letters, Arts and Sciences, Los Angeles, California, United States of America
- Biochemistry and Molecular Medicine Department, USC Keck School of Medicine, Los Angeles, California, United States of America
- USC Norris Comprehensive Cancer Center, Epigenetics and Gene Regulation, Los Angeles, California, United States of America
- USC Stem Cell Initiative, Los Angeles, California, United States of America
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Lee M, Ahmad SF, Xu J. Regulation and function of transposable elements in cancer genomes. Cell Mol Life Sci 2024; 81:157. [PMID: 38556602 PMCID: PMC10982106 DOI: 10.1007/s00018-024-05195-2] [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] [Received: 12/03/2023] [Revised: 02/28/2024] [Accepted: 03/01/2024] [Indexed: 04/02/2024]
Abstract
Over half of human genomic DNA is composed of repetitive sequences generated throughout evolution by prolific mobile genetic parasites called transposable elements (TEs). Long disregarded as "junk" or "selfish" DNA, TEs are increasingly recognized as formative elements in genome evolution, wired intimately into the structure and function of the human genome. Advances in sequencing technologies and computational methods have ushered in an era of unprecedented insight into how TE activity impacts human biology in health and disease. Here we discuss the current views on how TEs have shaped the regulatory landscape of the human genome, how TE activity is implicated in human cancers, and how recent findings motivate novel strategies to leverage TE activity for improved cancer therapy. Given the crucial role of methodological advances in TE biology, we pair our conceptual discussions with an in-depth review of the inherent technical challenges in studying repeats, specifically related to structural variation, expression analyses, and chromatin regulation. Lastly, we provide a catalog of existing and emerging assays and bioinformatic software that altogether are enabling the most sophisticated and comprehensive investigations yet into the regulation and function of interspersed repeats in cancer genomes.
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Affiliation(s)
- Michael Lee
- Department of Pediatrics, Children's Medical Center Research Institute, University of Texas Southwestern Medical Center, 6000 Harry Hines Blvd., Dallas, TX, 75390, USA.
| | - Syed Farhan Ahmad
- Department of Pathology, Center of Excellence for Leukemia Studies, St. Jude Children's Research Hospital, 262 Danny Thomas Place - MS 345, Memphis, TN, 38105, USA
| | - Jian Xu
- Department of Pathology, Center of Excellence for Leukemia Studies, St. Jude Children's Research Hospital, 262 Danny Thomas Place - MS 345, Memphis, TN, 38105, USA.
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Tong B, Sun Y. Activation of Young LINE-1 Elements by CRISPRa. Int J Mol Sci 2023; 25:424. [PMID: 38203595 PMCID: PMC10778729 DOI: 10.3390/ijms25010424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 12/26/2023] [Accepted: 12/26/2023] [Indexed: 01/12/2024] Open
Abstract
Long interspersed element-1 (LINE-1; L1s) are mobile genetic elements that comprise nearly 20% of the human genome. L1s have been shown to have important functions in various biological processes, and their dysfunction is thought to be linked with diseases and cancers. However, the roles of the repetitive elements are largely not understood. While the CRISPR activation (CRISPRa) system based on catalytically deadCas9 (dCas9) is widely used for genome-wide interrogation of gene function and genetic interaction, few studies have been conducted on L1s. Here, we report using the CRISPRa method to efficiently activate L1s in human L02 cells, a derivative of the HeLa cancer cell line. After CRISPRa, the young L1 subfamilies such as L1HS/L1PA1 and L1PA2 are found to be expressed at higher levels than the older L1s. The L1s with high levels of transcription are closer to full-length and are more densely occupied by the YY1 transcription factor. The activated L1s can either be mis-spliced to form chimeric transcripts or act as alternative promoters or enhancers to facilitate the expression of neighboring genes. The method described here can be used for studying the functional roles of young L1s in cultured cells of interest.
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Affiliation(s)
- Bei Tong
- Key Laboratory of Breeding Biotechnology and Sustainable Aquaculture, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Yuhua Sun
- Key Laboratory of Breeding Biotechnology and Sustainable Aquaculture, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
- The Innovation of Seed Design, Chinese Academy of Sciences, Wuhan 430072, China
- Hubei Hongshan Laboratory, Wuhan 430070, China
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Fu J, Qin T, Li C, Zhu J, Ding Y, Zhou M, Yang Q, Liu X, Zhou J, Chen F. Research progress of LINE-1 in the diagnosis, prognosis, and treatment of gynecologic tumors. Front Oncol 2023; 13:1201568. [PMID: 37546391 PMCID: PMC10399582 DOI: 10.3389/fonc.2023.1201568] [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: 04/06/2023] [Accepted: 06/19/2023] [Indexed: 08/08/2023] Open
Abstract
The retrotransposon known as long interspersed nuclear element-1 (LINE-1), which is currently the sole autonomously mobile transposon in the human genome, can result in insertional mutations, chromosomal rearrangements, and genomic instability. In recent years, numerous studies have shown that LINE-1 is involved in the development of various diseases and also plays an important role in the immune regulation of the organism. The expression of LINE-1 in gynecologic tumors suggests that it is expected to be an independent indicator for early diagnosis and prognosis, and also, as a therapeutic target, LINE-1 is closely associated with gynecologic tumor prognosis. This article discusses the function of LINE-1 in the diagnosis, treatment, and prognosis of ovarian, cervical, and endometrial malignancies, as well as other gynecologic malignancies. It offers fresh perspectives on the early detection of tumors and the creation of novel anti-tumor medications.
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Affiliation(s)
- Jiaojiao Fu
- The First Clinical Medical College of Gansu University of Chinese Medicine, Gansu Provincial Hospital, Lanzhou, China
- Department of Obstetrics and Gynecology, Gansu Provincial Hospital, Lanzhou, Gansu, China
| | - Tiansheng Qin
- The First Clinical Medical College of Gansu University of Chinese Medicine, Gansu Provincial Hospital, Lanzhou, China
- Department of Obstetrics and Gynecology, Gansu Provincial Hospital, Lanzhou, Gansu, China
- The First Clinical Medical School, Lanzhou University, Lanzhou, Gansu, China
- National Health Commission (NHC) Key Laboratory of Diagnosis and Therapy of Gastrointestinal Tumor, Gansu Provincial Hospital, Lanzhou, Gansu, China
| | - Chaoming Li
- The First People’s Hospital of Longnan, Longnan City Hospital, Longnan, Gansu, China
| | - Jiaojiao Zhu
- The First Clinical Medical College of Gansu University of Chinese Medicine, Gansu Provincial Hospital, Lanzhou, China
- Department of Obstetrics and Gynecology, Gansu Provincial Hospital, Lanzhou, Gansu, China
| | - Yaoyao Ding
- The First Clinical Medical College of Gansu University of Chinese Medicine, Gansu Provincial Hospital, Lanzhou, China
- Department of Obstetrics and Gynecology, Gansu Provincial Hospital, Lanzhou, Gansu, China
| | - Meiying Zhou
- Department of Obstetrics and Gynecology, Gansu Provincial Hospital, Lanzhou, Gansu, China
| | - Qing Yang
- The First Clinical Medical College of Gansu University of Chinese Medicine, Gansu Provincial Hospital, Lanzhou, China
- Department of Obstetrics and Gynecology, Gansu Provincial Hospital, Lanzhou, Gansu, China
| | - Xiaofeng Liu
- The First Clinical Medical College of Gansu University of Chinese Medicine, Gansu Provincial Hospital, Lanzhou, China
- Department of Obstetrics and Gynecology, Gansu Provincial Hospital, Lanzhou, Gansu, China
| | - Juanhong Zhou
- The First Clinical Medical College of Gansu University of Chinese Medicine, Gansu Provincial Hospital, Lanzhou, China
- Department of Obstetrics and Gynecology, Gansu Provincial Hospital, Lanzhou, Gansu, China
| | - Fan Chen
- The First Clinical Medical College of Gansu University of Chinese Medicine, Gansu Provincial Hospital, Lanzhou, China
- Department of Obstetrics and Gynecology, Gansu Provincial Hospital, Lanzhou, Gansu, China
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Kong L, Saha K, Hu Y, Tschetter JN, Habben CE, Whitmore LS, Yao C, Ge X, Ye P, Newkirk SJ, An W. Subfamily-specific differential contribution of individual monomers and the tether sequence to mouse L1 promoter activity. Mob DNA 2022; 13:13. [PMID: 35443687 PMCID: PMC9022269 DOI: 10.1186/s13100-022-00269-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Accepted: 03/28/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The internal promoter in L1 5'UTR is critical for autonomous L1 transcription and initiating retrotransposition. Unlike the human genome, which features one contemporarily active subfamily, four subfamilies (A_I, Gf_I and Tf_I/II) have been amplifying in the mouse genome in the last one million years. Moreover, mouse L1 5'UTRs are organized into tandem repeats called monomers, which are separated from ORF1 by a tether domain. In this study, we aim to compare promoter activities across young mouse L1 subfamilies and investigate the contribution of individual monomers and the tether sequence. RESULTS We observed an inverse relationship between subfamily age and the average number of monomers among evolutionarily young mouse L1 subfamilies. The youngest subgroup (A_I and Tf_I/II) on average carry 3-4 monomers in the 5'UTR. Using a single-vector dual-luciferase reporter assay, we compared promoter activities across six L1 subfamilies (A_I/II, Gf_I and Tf_I/II/III) and established their antisense promoter activities in a mouse embryonic fibroblast cell line and a mouse embryonal carcinoma cell line. Using consensus promoter sequences for three subfamilies (A_I, Gf_I and Tf_I), we dissected the differential roles of individual monomers and the tether domain in L1 promoter activity. We validated that, across multiple subfamilies, the second monomer consistently enhances the overall promoter activity. For individual promoter components, monomer 2 is consistently more active than the corresponding monomer 1 and/or the tether for each subfamily. Importantly, we revealed intricate interactions between monomer 2, monomer 1 and tether domains in a subfamily-specific manner. Furthermore, using three-monomer 5'UTRs, we established a complex nonlinear relationship between the length of the outmost monomer and the overall promoter activity. CONCLUSIONS The laboratory mouse is an important mammalian model system for human diseases as well as L1 biology. Our study extends previous findings and represents an important step toward a better understanding of the molecular mechanism controlling mouse L1 transcription as well as L1's impact on development and disease.
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Affiliation(s)
- Lingqi Kong
- Department of Pharmaceutical Sciences, South Dakota State University, Brookings, SD, 57007, USA
| | - Karabi Saha
- Department of Pharmaceutical Sciences, South Dakota State University, Brookings, SD, 57007, USA
| | - Yuchi Hu
- Department of Pharmaceutical Sciences, South Dakota State University, Brookings, SD, 57007, USA
| | - Jada N Tschetter
- Department of Pharmaceutical Sciences, South Dakota State University, Brookings, SD, 57007, USA
| | - Chase E Habben
- Department of Pharmaceutical Sciences, South Dakota State University, Brookings, SD, 57007, USA
| | - Leanne S Whitmore
- Department of Immunology, University of Washington, Seattle, WA, 98109, USA
| | - Changfeng Yao
- Anhui University of Traditional Chinese Medicine, Hefei, 230012, Anhui, China
| | - Xijin Ge
- Department of Mathematics & Statistics, South Dakota State University, Brookings, SD, 57007, USA
| | - Ping Ye
- Department of Pharmacy Practice, South Dakota State University, Brookings, SD, 57007, USA
| | - Simon J Newkirk
- Department of Pharmaceutical Sciences, South Dakota State University, Brookings, SD, 57007, USA
| | - Wenfeng An
- Department of Pharmaceutical Sciences, South Dakota State University, Brookings, SD, 57007, USA.
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Factors Regulating the Activity of LINE1 Retrotransposons. Genes (Basel) 2021; 12:genes12101562. [PMID: 34680956 PMCID: PMC8535693 DOI: 10.3390/genes12101562] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Revised: 09/21/2021] [Accepted: 09/22/2021] [Indexed: 12/15/2022] Open
Abstract
LINE-1 (L1) is a class of autonomous mobile genetic elements that form somatic mosaicisms in various tissues of the organism. The activity of L1 retrotransposons is strictly controlled by many factors in somatic and germ cells at all stages of ontogenesis. Alteration of L1 activity was noted in a number of diseases: in neuropsychiatric and autoimmune diseases, as well as in various forms of cancer. Altered activity of L1 retrotransposons for some pathologies is associated with epigenetic changes and defects in the genes involved in their repression. This review discusses the molecular genetic mechanisms of the retrotransposition and regulation of the activity of L1 elements. The contribution of various factors controlling the expression and distribution of L1 elements in the genome occurs at all stages of the retrotransposition. The regulation of L1 elements at the transcriptional, post-transcriptional and integration into the genome stages is described in detail. Finally, this review also focuses on the evolutionary aspects of L1 accumulation and their interplay with the host regulation system.
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