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Blumenstiel JP. From the cauldron of conflict: Endogenous gene regulation by piRNA and other modes of adaptation enabled by selfish transposable elements. Semin Cell Dev Biol 2025; 164:1-12. [PMID: 38823219 DOI: 10.1016/j.semcdb.2024.05.001] [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: 10/10/2023] [Revised: 04/28/2024] [Accepted: 05/06/2024] [Indexed: 06/03/2024]
Abstract
Transposable elements (TEs) provide a prime example of genetic conflict because they can proliferate in genomes and populations even if they harm the host. However, numerous studies have shown that TEs, though typically harmful, can also provide fuel for adaptation. This is because they code functional sequences that can be useful for the host in which they reside. In this review, I summarize the "how" and "why" of adaptation enabled by the genetic conflict between TEs and hosts. In addition, focusing on mechanisms of TE control by small piwi-interacting RNAs (piRNAs), I highlight an indirect form of adaptation enabled by conflict. In this case, mechanisms of host defense that regulate TEs have been redeployed for endogenous gene regulation. I propose that the genetic conflict released by meiosis in early eukaryotes may have been important because, among other reasons, it spurred evolutionary innovation on multiple interwoven trajectories - on the part of hosts and also embedded genetic parasites. This form of evolution may function as a complexity generating engine that was a critical player in eukaryotic evolution.
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Affiliation(s)
- Justin P Blumenstiel
- Department of Ecology and Evolutionary Biology, University of Kansas, 1200 Sunnyside Avenue, Lawrence, KS 66045, United States.
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Dorador AP, Dalikova M, Cerbin S, Stillman CM, Zych MG, Hawley RS, Miller DE, Ray DA, Funikov SY, Evgen’ev MB, Blumenstiel JP. Paramutation-like Epigenetic Conversion by piRNA at the Telomere of Drosophila virilis. BIOLOGY 2022; 11:biology11101480. [PMID: 36290385 PMCID: PMC9598792 DOI: 10.3390/biology11101480] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Revised: 09/27/2022] [Accepted: 10/04/2022] [Indexed: 11/10/2022]
Abstract
First discovered in maize, paramutation is a phenomenon in which one allele can trigger an epigenetic conversion of an alternate allele. This conversion causes a genetically heterozygous individual to transmit alleles that are functionally the same, in apparent violation of Mendelian segregation. Studies over the past several decades have revealed a strong connection between mechanisms of genome defense against transposable elements by small RNA and the phenomenon of paramutation. For example, a system of paramutation in Drosophila melanogaster has been shown to be mediated by piRNAs, whose primary function is to silence transposable elements in the germline. In this paper, we characterize a second system of piRNA-mediated paramutation-like behavior at the telomere of Drosophila virilis. In Drosophila, telomeres are maintained by arrays of retrotransposons that are regulated by piRNAs. As a result, the telomere and sub-telomeric regions of the chromosome have unique regulatory and chromatin properties. Previous studies have shown that maternally deposited piRNAs derived from a sub-telomeric piRNA cluster can silence the sub-telomeric center divider gene of Drosophila virilis in trans. In this paper, we show that this silencing can also be maintained in the absence of the original silencing allele in a subsequent generation. The precise mechanism of this paramutation-like behavior may be explained by either the production of retrotransposon piRNAs that differ across strains or structural differences in the telomere. Altogether, these results show that the capacity for piRNAs to mediate paramutation in trans may depend on the local chromatin environment and proximity to the uniquely structured telomere regulated by piRNAs. This system promises to provide significant insights into the mechanisms of paramutation.
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Affiliation(s)
- Ana P. Dorador
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045, USA
| | - Martina Dalikova
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045, USA
| | - Stefan Cerbin
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045, USA
| | - Chris M. Stillman
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045, USA
| | - Molly G. Zych
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
- Divisions of Basic Sciences and Human Biology, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - R. Scott Hawley
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
- Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - Danny E. Miller
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
- Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160, USA
- Division of Genetic Medicine, Department of Pediatrics, University of Washington and Seattle Children’s Hospital, Seattle, WA 98195, USA
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA 98195, USA
| | - David A. Ray
- Department of Biological Sciences, Texas Tech University, Lubbock, TX 79409, USA
| | - Sergei Y. Funikov
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow 119991, Russia
| | - Michael B. Evgen’ev
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow 119991, Russia
| | - Justin P. Blumenstiel
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045, USA
- Correspondence:
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Ellison CE, Kagda MS, Cao W. Telomeric TART elements target the piRNA machinery in Drosophila. PLoS Biol 2020; 18:e3000689. [PMID: 33347429 PMCID: PMC7785250 DOI: 10.1371/journal.pbio.3000689] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 01/05/2021] [Accepted: 12/10/2020] [Indexed: 11/23/2022] Open
Abstract
Coevolution between transposable elements (TEs) and their hosts can be antagonistic, where TEs evolve to avoid silencing and the host responds by reestablishing TE suppression, or mutualistic, where TEs are co-opted to benefit their host. The TART-A TE functions as an important component of Drosophila telomeres but has also reportedly inserted into the Drosophila melanogaster nuclear export factor gene nxf2. We find that, rather than inserting into nxf2, TART-A has actually captured a portion of nxf2 sequence. We show that TART-A produces abundant Piwi-interacting small RNAs (piRNAs), some of which are antisense to the nxf2 transcript, and that the TART-like region of nxf2 is evolving rapidly. Furthermore, in D. melanogaster, TART-A is present at higher copy numbers, and nxf2 shows reduced expression, compared to the closely related species Drosophila simulans. We propose that capturing nxf2 sequence allowed TART-A to target the nxf2 gene for piRNA-mediated repression and that these 2 elements are engaged in antagonistic coevolution despite the fact that TART-A is serving a critical role for its host genome. Co-evolution between transposable elements (TEs) and their hosts can be antagonistic, where TEs evolve to avoid silencing and the host responds by re-establishing TE suppression, or mutualistic, where TEs are co-opted to benefit their host. This study shows that a specialized Drosophila retrotransposon that functions as a telomere has captured a portion of a host piRNA gene which may allow it to evade silencing.
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Affiliation(s)
- Christopher E. Ellison
- Department of Genetics, Human Genetics Institute of New Jersey, Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States of America
- * E-mail:
| | - Meenakshi S. Kagda
- Department of Genetics, Human Genetics Institute of New Jersey, Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States of America
| | - Weihuan Cao
- Department of Genetics, Human Genetics Institute of New Jersey, Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States of America
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Lakhotia SC. Non-coding RNAs demystify constitutive heterochromatin as essential modulator of epigenotype. THE NUCLEUS 2017. [DOI: 10.1007/s13237-017-0221-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
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Specific Localization of the Drosophila Telomere Transposon Proteins and RNAs, Give Insight in Their Behavior, Control and Telomere Biology in This Organism. PLoS One 2015; 10:e0128573. [PMID: 26068215 PMCID: PMC4467039 DOI: 10.1371/journal.pone.0128573] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Accepted: 04/28/2015] [Indexed: 01/02/2023] Open
Abstract
Drosophila telomeres constitute a remarkable exception to the telomerase mechanism. Although maintaining the same cytological and functional properties as telomerase maintain telomeres, Drosophila telomeres embed the telomere retrotransposons whose specific and highly regulated terminal transposition maintains the appropriate telomere length in this organism. Nevertheless, our current understanding of how the mechanism of the retrotransposon telomere works and which features are shared with the telomerase system is very limited. We report for the first time a detailed study of the localization of the main components that constitute the telomeres in Drosophila, HeT-A and TART RNAs and proteins. Our results in wild type and mutant strains reveal localizations of HeT-A Gag and TART Pol that give insight in the behavior of the telomere retrotransposons and their control. We find that TART Pol and HeT-A Gag only co-localize at the telomeres during the interphase of cells undergoing mitotic cycles. In addition, unexpected protein and RNA localizations with a well-defined pattern in cells such as the ovarian border cells and nurse cells, suggest possible strategies for the telomere transposons to reach the oocyte, and/or additional functions that might be important for the correct development of the organism. Finally, we have been able to visualize the telomere RNAs at different ovarian stages of development in wild type and mutant lines, demonstrating their presence in spite of being tightly regulated by the piRNA mechanism.
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Song J, Liu J, Schnakenberg SL, Ha H, Xing J, Chen KC. Variation in piRNA and transposable element content in strains of Drosophila melanogaster. Genome Biol Evol 2014; 6:2786-98. [PMID: 25267446 PMCID: PMC4224344 DOI: 10.1093/gbe/evu217] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Transposable elements (TEs) are one of the most important features of genome architecture, so their evolution and relationship with host defense mechanisms have been topics of intense study, especially in model systems such as Drosophila melanogaster. Recently, a novel small RNA-based defense mechanism in animals called the Piwi-interacting RNA (piRNA) pathway was discovered to form an adaptive defense mechanism against TEs. To investigate the relationship between piRNA and TE content between strains of a species, we sequenced piRNAs from 16 inbred lines of D. melanogaster from the Drosophila Genetic Reference Panel. Instead of a global correlation of piRNA expression and TE content, we found evidence for a host response through de novo piRNA production from novel TE insertions. Although approximately 20% of novel TE insertions induced de novo piRNA production, the abundance of de novo piRNAs was low and did not markedly affect the global pool of ovarian piRNAs. Our results provide new insights into the evolution of TEs and the piRNA system in an important model organism.
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Affiliation(s)
- Jimin Song
- Department of Genetics, Rutgers University BioMaPS Institute for Quantitative Biology, Rutgers University
| | - Jixia Liu
- Department of Genetics, Rutgers University BioMaPS Institute for Quantitative Biology, Rutgers University Human Genetics Institute of New Jersey, Rutgers University
| | - Sandra L Schnakenberg
- Department of Genetics, Rutgers University BioMaPS Institute for Quantitative Biology, Rutgers University Developmental Biology Program, Sloan-Kettering Institute, New York, NY
| | - Hongseok Ha
- Department of Genetics, Rutgers University Human Genetics Institute of New Jersey, Rutgers University
| | - Jinchuan Xing
- Department of Genetics, Rutgers University Human Genetics Institute of New Jersey, Rutgers University
| | - Kevin C Chen
- Department of Genetics, Rutgers University BioMaPS Institute for Quantitative Biology, Rutgers University
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Minakhina S, Changela N, Steward R. Zfrp8/PDCD2 is required in ovarian stem cells and interacts with the piRNA pathway machinery. Development 2014; 141:259-68. [PMID: 24381196 DOI: 10.1242/dev.101410] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The maintenance of stem cells is central to generating diverse cell populations in many tissues throughout the life of an animal. Elucidating the mechanisms involved in how stem cells are formed and maintained is crucial to understanding both normal developmental processes and the growth of many cancers. Previously, we showed that Zfrp8/PDCD2 is essential for the maintenance of Drosophila hematopoietic stem cells. Here, we show that Zfrp8/PDCD2 is also required in both germline and follicle stem cells in the Drosophila ovary. Expression of human PDCD2 fully rescues the Zfrp8 phenotype, underlining the functional conservation of Zfrp8/PDCD2. The piRNA pathway is essential in early oogenesis, and we find that nuclear localization of Zfrp8 in germline stem cells and their offspring is regulated by some piRNA pathway genes. We also show that Zfrp8 forms a complex with the piRNA pathway protein Maelstrom and controls the accumulation of Maelstrom in the nuage. Furthermore, Zfrp8 regulates the activity of specific transposable elements also controlled by Maelstrom and Piwi. Our results suggest that Zfrp8/PDCD2 is not an integral member of the piRNA pathway, but has an overlapping function, possibly competing with Maelstrom and Piwi.
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Affiliation(s)
- Svetlana Minakhina
- Rutgers University, Department of Molecular Biology, Waksman Institute, Cancer Institute of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ 08854, USA
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Castel SE, Martienssen RA. RNA interference in the nucleus: roles for small RNAs in transcription, epigenetics and beyond. Nat Rev Genet 2013; 14:100-12. [PMID: 23329111 DOI: 10.1038/nrg3355] [Citation(s) in RCA: 674] [Impact Index Per Article: 61.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A growing number of functions are emerging for RNA interference (RNAi) in the nucleus, in addition to well-characterized roles in post-transcriptional gene silencing in the cytoplasm. Epigenetic modifications directed by small RNAs have been shown to cause transcriptional repression in plants, fungi and animals. Additionally, increasing evidence indicates that RNAi regulates transcription through interaction with transcriptional machinery. Nuclear small RNAs include small interfering RNAs (siRNAs) and PIWI-interacting RNAs (piRNAs) and are implicated in nuclear processes such as transposon regulation, heterochromatin formation, developmental gene regulation and genome stability.
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Affiliation(s)
- Stephane E Castel
- Watson School of Biological Sciences, Cold Spring Harbor Laboratory, New York 11724, USA
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Abstract
Many aspects of gene regulation are mediated by RNA molecules. However, regulatory RNAs have remained elusive until very recently. At least three types of small regulatory RNAs have been characterized in Drosophila: microRNAs (miRNAs), piwi-interacting RNAs and endogenous siRNAs. A fourth class of regulatory RNAs includes known long non-coding RNAs such as roX1 or bxd. The initial sequencing of the Drosophila melanogaster genome has served as a scaffold to study the transcriptional profile of an animal, revealing the complexities of the function and biogenesis of regulatory RNAs. The comparative analysis of 12 Drosophila genomes has been crucial for the study of microRNA evolution. However, comparative genomics of other RNA regulators is confounded by technical problems: genomic loci are poorly conserved and frequently encoded in the heterochromatin. Future developments in genome sequencing and population genomics in Drosophila will continue to shed light on the conservation, evolution and function of regulatory RNAs.
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Affiliation(s)
- Antonio Marco
- University of Manchester, Michael Smith Building, Manchester, UK.
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