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Angel SO, Vanagas L, Alonso AM. Mechanisms of adaptation and evolution in Toxoplasma gondii. Mol Biochem Parasitol 2024; 258:111615. [PMID: 38354788 DOI: 10.1016/j.molbiopara.2024.111615] [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: 09/15/2023] [Revised: 12/28/2023] [Accepted: 02/06/2024] [Indexed: 02/16/2024]
Abstract
Toxoplasma has high host flexibility, infecting all nucleated cells of mammals and birds. This implies that during its infective process the parasite must constantly adapt to different environmental situations, which in turn leads to modifications in its metabolism, regulation of gene transcription, translation of mRNAs and stage specific factors. There are conserved pathways that support these adaptations, which we aim to elucidate in this review. We begin by exploring the widespread epigenetic mechanisms and transcription regulators, continue with the supportive role of Heat Shock Proteins (Hsp), the translation regulation, stress granules, and finish with the emergence of contingency genes in highly variable genomic domains, such as subtelomeres. Within epigenetics, the discovery of a new histone variant of the H2B family (H2B.Z), contributing to T. gondii virulence and differentiation, but also gene expression regulation and its association with the metabolic state of the parasite, is highlighted. Associated with the regulation of gene expression are transcription factors (TFs). An overview of the main findings on TF and development is presented. We also emphasize the role of Hsp90 and Tgj1 in T. gondii metabolic fitness and the regulation of protein translation. Translation regulation is also highlighted as a mechanism for adaptation to conditions encountered by the parasite as well as stress granules containing mRNA and proteins generated in the extracellular tachyzoite. Another important aspect in evolution and adaptability are the subtelomeres because of their high variability and gene duplication rate. Toxoplasma possess multigene families of membrane proteins and contingency genes that are associated with different metabolic stresses. Among them parasite differentiation and environmental stresses stand out, including those that lead tachyzoite to bradyzoite conversion. Finally, we are interested in positioning protozoa as valuable evolution models, focusing on research related to the Extended Evolutionary Synthesis, based on models recently generated, such as extracellular adaptation and ex vivo cyst recrudescence.
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Affiliation(s)
- Sergio O Angel
- Laboratorio de Parasitología Molecular, INTECH, CONICET-UNSAM, Av. Intendente Marino Km. 8.2, C.C 164, (B7130IIWA), Chascomús, Prov, Buenos Aires, Argentina.
| | - Laura Vanagas
- Laboratorio de Parasitología Molecular, INTECH, CONICET-UNSAM, Av. Intendente Marino Km. 8.2, C.C 164, (B7130IIWA), Chascomús, Prov, Buenos Aires, Argentina.
| | - Andres M Alonso
- Laboratorio de Parasitología Molecular, INTECH, CONICET-UNSAM, Av. Intendente Marino Km. 8.2, C.C 164, (B7130IIWA), Chascomús, Prov, Buenos Aires, Argentina.
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2
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Brann T, Beltramini A, Chaparro C, Berriman M, Doyle SR, Protasio AV. Subtelomeric plasticity contributes to gene family expansion in the human parasitic flatworm Schistosoma mansoni. BMC Genomics 2024; 25:217. [PMID: 38413905 PMCID: PMC10900676 DOI: 10.1186/s12864-024-10032-8] [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: 10/03/2023] [Accepted: 01/19/2024] [Indexed: 02/29/2024] Open
Abstract
BACKGROUND The genomic region that lies between the telomere and chromosome body, termed the subtelomere, is heterochromatic, repeat-rich, and frequently undergoes rearrangement. Within this region, large-scale structural changes enable gene diversification, and, as such, large multicopy gene families are often found at the subtelomere. In some parasites, genes associated with proliferation, invasion, and survival are often found in these regions, where they benefit from the subtelomere's highly plastic, rapidly changing nature. The increasing availability of complete (or near complete) parasite genomes provides an opportunity to investigate these typically poorly defined and overlooked genomic regions and potentially reveal relevant gene families necessary for the parasite's lifestyle. RESULTS Using the latest chromosome-scale genome assembly and hallmark repeat richness observed at chromosome termini, we have identified and characterised the subtelomeres of Schistosoma mansoni, a metazoan parasitic flatworm that infects over 250 million people worldwide. Approximately 12% of the S. mansoni genome is classified as subtelomeric, and, in line with other organisms, we find these regions to be gene-poor but rich in transposable elements. We find that S. mansoni subtelomeres have undergone extensive interchromosomal recombination and that these sites disproportionately contribute to the 2.3% of the genome derived from segmental duplications. This recombination has led to the expansion of subtelomeric gene clusters containing 103 genes, including the immunomodulatory annexins and other gene families with unknown roles. The largest of these is a 49-copy plexin domain-containing protein cluster, exclusively expressed in the tegument-the tissue located at the host-parasite physical interface-of intramolluscan life stages. CONCLUSIONS We propose that subtelomeric regions act as a genomic playground for trial-and-error of gene duplication and subsequent divergence. Owing to the importance of subtelomeric genes in other parasites, gene families implicated in this subtelomeric expansion within S. mansoni warrant further characterisation for a potential role in parasitism.
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Affiliation(s)
- T Brann
- Department of Pathology, University of Cambridge, Cambridge, CB1 2PQ, UK
| | - A Beltramini
- Department of Pathology, University of Cambridge, Cambridge, CB1 2PQ, UK
| | - C Chaparro
- IHPE, CNRS, IFREMER, UPVD, University Montpellier, Perpignan, F-66860, France
| | - M Berriman
- School of Infection and Immunity, University of Glasgow, Glasgow, G12 8TA, UK
| | - S R Doyle
- Wellcome Sanger Institute, Cambridge, CB10 1SA, UK
| | - A V Protasio
- Department of Pathology, University of Cambridge, Cambridge, CB1 2PQ, UK.
- Christ's College, Cambridge, CB2 3BU, UK.
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Čapková Frydrychová R, Mason JM, Peska V. Editorial: Telomere Flexibility and Versatility: A Role of Telomeres in Adaptive Potential. Front Genet 2021; 12:771938. [PMID: 34671387 PMCID: PMC8520972 DOI: 10.3389/fgene.2021.771938] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Accepted: 09/15/2021] [Indexed: 11/30/2022] Open
Affiliation(s)
- Radmila Čapková Frydrychová
- Institute of Entomology, Biology Centre of the Czech Academy of Sciences, České Budějovice, Czechia.,Faculty of Science, University of South Bohemia, České Budějovice, Czechia
| | | | - Vratislav Peska
- Department of Cell Biology and Radiobiology, Institute of Biophysics of the Czech Academy of Sciences, Brno, Czechia
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Rahnama M, Wang B, Dostart J, Novikova O, Yackzan D, Yackzan A, Bruss H, Baker M, Jacob H, Zhang X, Lamb A, Stewart A, Heist M, Hoover J, Calie P, Chen L, Liu J, Farman ML. Telomere Roles in Fungal Genome Evolution and Adaptation. Front Genet 2021; 12:676751. [PMID: 34434216 PMCID: PMC8381367 DOI: 10.3389/fgene.2021.676751] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Accepted: 06/28/2021] [Indexed: 11/27/2022] Open
Abstract
Telomeres form the ends of linear chromosomes and usually comprise protein complexes that bind to simple repeated sequence motifs that are added to the 3′ ends of DNA by the telomerase reverse transcriptase (TERT). One of the primary functions attributed to telomeres is to solve the “end-replication problem” which, if left unaddressed, would cause gradual, inexorable attrition of sequences from the chromosome ends and, eventually, loss of viability. Telomere-binding proteins also protect the chromosome from 5′ to 3′ exonuclease action, and disguise the chromosome ends from the double-strand break repair machinery whose illegitimate action potentially generates catastrophic chromosome aberrations. Telomeres are of special interest in the blast fungus, Pyricularia, because the adjacent regions are enriched in genes controlling interactions with host plants, and the chromosome ends show enhanced polymorphism and genetic instability. Previously, we showed that telomere instability in some P. oryzae strains is caused by novel retrotransposons (MoTeRs) that insert in telomere repeats, generating interstitial telomere sequences that drive frequent, break-induced rearrangements. Here, we sought to gain further insight on telomeric involvement in shaping Pyricularia genome architecture by characterizing sequence polymorphisms at chromosome ends, and surrounding internalized MoTeR loci (relics) and interstitial telomere repeats. This provided evidence that telomere dynamics have played historical, and likely ongoing, roles in shaping the Pyricularia genome. We further demonstrate that even telomeres lacking MoTeR insertions are poorly preserved, such that the telomere-adjacent sequences exhibit frequent presence/absence polymorphism, as well as exchanges with the genome interior. Using TERT knockout experiments, we characterized chromosomal responses to failed telomere maintenance which suggested that much of the MoTeR relic-/interstitial telomere-associated polymorphism could be driven by compromised telomere function. Finally, we describe three possible examples of a phenomenon known as “Adaptive Telomere Failure,” where spontaneous losses of telomere maintenance drive rapid accumulation of sequence polymorphism with possible adaptive advantages. Together, our data suggest that telomere maintenance is frequently compromised in Pyricularia but the chromosome alterations resulting from telomere failure are not as catastrophic as prior research would predict, and may, in fact, be potent drivers of adaptive polymorphism.
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Affiliation(s)
- Mostafa Rahnama
- Department of Plant Pathology, University of Kentucky, Lexington, KY, United States
| | - Baohua Wang
- Department of Plant Pathology, University of Kentucky, Lexington, KY, United States.,State Key Laboratory for Ecological Pest Control of Fujian and Taiwan Crops, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Jane Dostart
- Department of Biological Sciences, Eastern Kentucky University, Richmond, KY, United States
| | - Olga Novikova
- Department of Plant Pathology, University of Kentucky, Lexington, KY, United States
| | - Daniel Yackzan
- Department of Plant Pathology, University of Kentucky, Lexington, KY, United States
| | - Andrew Yackzan
- Department of Plant Pathology, University of Kentucky, Lexington, KY, United States
| | - Haley Bruss
- Department of Biological Sciences, Eastern Kentucky University, Richmond, KY, United States
| | - Maray Baker
- Department of Biological Sciences, Eastern Kentucky University, Richmond, KY, United States
| | - Haven Jacob
- Department of Biological Sciences, Eastern Kentucky University, Richmond, KY, United States
| | - Xiaofei Zhang
- Department of Computer Sciences, University of Kentucky, Lexington, KY, United States
| | - April Lamb
- Department of Plant Pathology, University of Kentucky, Lexington, KY, United States
| | - Alex Stewart
- Department of Plant Pathology, University of Kentucky, Lexington, KY, United States
| | - Melanie Heist
- Department of Plant Pathology, University of Kentucky, Lexington, KY, United States
| | - Joey Hoover
- Department of Plant Pathology, University of Kentucky, Lexington, KY, United States
| | - Patrick Calie
- Department of Biological Sciences, Eastern Kentucky University, Richmond, KY, United States
| | - Li Chen
- Department of Plant Pathology, University of Kentucky, Lexington, KY, United States
| | - Jinze Liu
- Department of Computer Sciences, University of Kentucky, Lexington, KY, United States
| | - Mark L Farman
- Department of Plant Pathology, University of Kentucky, Lexington, KY, United States
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5
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Li Y, Leveau A, Zhao Q, Feng Q, Lu H, Miao J, Xue Z, Martin AC, Wegel E, Wang J, Orme A, Rey MD, Karafiátová M, Vrána J, Steuernagel B, Joynson R, Owen C, Reed J, Louveau T, Stephenson MJ, Zhang L, Huang X, Huang T, Fan D, Zhou C, Tian Q, Li W, Lu Y, Chen J, Zhao Y, Lu Y, Zhu C, Liu Z, Polturak G, Casson R, Hill L, Moore G, Melton R, Hall N, Wulff BBH, Doležel J, Langdon T, Han B, Osbourn A. Subtelomeric assembly of a multi-gene pathway for antimicrobial defense compounds in cereals. Nat Commun 2021; 12:2563. [PMID: 33963185 PMCID: PMC8105312 DOI: 10.1038/s41467-021-22920-8] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Accepted: 04/07/2021] [Indexed: 02/06/2023] Open
Abstract
Non-random gene organization in eukaryotes plays a significant role in genome evolution. Here, we investigate the origin of a biosynthetic gene cluster for production of defence compounds in oat-the avenacin cluster. We elucidate the structure and organisation of this 12-gene cluster, characterise the last two missing pathway steps, and reconstitute the entire pathway in tobacco by transient expression. We show that the cluster has formed de novo since the divergence of oats in a subtelomeric region of the genome that lacks homology with other grasses, and that gene order is approximately colinear with the biosynthetic pathway. We speculate that the positioning of the late pathway genes furthest away from the telomere may mitigate against a 'self-poisoning' scenario in which toxic intermediates accumulate as a result of telomeric gene deletions. Our investigations reveal a striking example of adaptive evolution underpinned by remarkable genome plasticity.
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Affiliation(s)
- Yan Li
- National Centre for Gene Research, CAS-JIC Centre of Excellence for Plant and Microbial Science (CEPAMS), Centre of Excellence for Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences (CAS), Shanghai, China
| | | | - Qiang Zhao
- National Centre for Gene Research, CAS-JIC Centre of Excellence for Plant and Microbial Science (CEPAMS), Centre of Excellence for Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences (CAS), Shanghai, China
| | - Qi Feng
- National Centre for Gene Research, CAS-JIC Centre of Excellence for Plant and Microbial Science (CEPAMS), Centre of Excellence for Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences (CAS), Shanghai, China
| | - Hengyun Lu
- National Centre for Gene Research, CAS-JIC Centre of Excellence for Plant and Microbial Science (CEPAMS), Centre of Excellence for Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences (CAS), Shanghai, China
| | - Jiashun Miao
- National Centre for Gene Research, CAS-JIC Centre of Excellence for Plant and Microbial Science (CEPAMS), Centre of Excellence for Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences (CAS), Shanghai, China
| | - Zheyong Xue
- John Innes Centre, Norwich Research Park, Norwich, UK
| | | | - Eva Wegel
- John Innes Centre, Norwich Research Park, Norwich, UK
| | - Jing Wang
- John Innes Centre, Norwich Research Park, Norwich, UK
| | | | | | - Miroslava Karafiátová
- Institute of Experimental Botany of the Czech Academy of Sciences, Centre of the Region Haná for Biotechnological and Agricultural Research, Olomouc, Czech Republic
| | - Jan Vrána
- Institute of Experimental Botany of the Czech Academy of Sciences, Centre of the Region Haná for Biotechnological and Agricultural Research, Olomouc, Czech Republic
| | | | - Ryan Joynson
- Earlham Institute, Norwich Research Park, Norwich, UK
| | | | - James Reed
- John Innes Centre, Norwich Research Park, Norwich, UK
| | | | | | - Lei Zhang
- National Centre for Gene Research, CAS-JIC Centre of Excellence for Plant and Microbial Science (CEPAMS), Centre of Excellence for Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences (CAS), Shanghai, China
| | - Xuehui Huang
- National Centre for Gene Research, CAS-JIC Centre of Excellence for Plant and Microbial Science (CEPAMS), Centre of Excellence for Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences (CAS), Shanghai, China
| | - Tao Huang
- National Centre for Gene Research, CAS-JIC Centre of Excellence for Plant and Microbial Science (CEPAMS), Centre of Excellence for Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences (CAS), Shanghai, China
| | - Danling Fan
- National Centre for Gene Research, CAS-JIC Centre of Excellence for Plant and Microbial Science (CEPAMS), Centre of Excellence for Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences (CAS), Shanghai, China
| | - Congcong Zhou
- National Centre for Gene Research, CAS-JIC Centre of Excellence for Plant and Microbial Science (CEPAMS), Centre of Excellence for Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences (CAS), Shanghai, China
| | - Qilin Tian
- National Centre for Gene Research, CAS-JIC Centre of Excellence for Plant and Microbial Science (CEPAMS), Centre of Excellence for Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences (CAS), Shanghai, China
| | - Wenjun Li
- National Centre for Gene Research, CAS-JIC Centre of Excellence for Plant and Microbial Science (CEPAMS), Centre of Excellence for Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences (CAS), Shanghai, China
| | - Yiqi Lu
- National Centre for Gene Research, CAS-JIC Centre of Excellence for Plant and Microbial Science (CEPAMS), Centre of Excellence for Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences (CAS), Shanghai, China
| | - Jiaying Chen
- National Centre for Gene Research, CAS-JIC Centre of Excellence for Plant and Microbial Science (CEPAMS), Centre of Excellence for Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences (CAS), Shanghai, China
| | - Yan Zhao
- National Centre for Gene Research, CAS-JIC Centre of Excellence for Plant and Microbial Science (CEPAMS), Centre of Excellence for Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences (CAS), Shanghai, China
| | - Ying Lu
- National Centre for Gene Research, CAS-JIC Centre of Excellence for Plant and Microbial Science (CEPAMS), Centre of Excellence for Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences (CAS), Shanghai, China
| | - Chuanrang Zhu
- National Centre for Gene Research, CAS-JIC Centre of Excellence for Plant and Microbial Science (CEPAMS), Centre of Excellence for Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences (CAS), Shanghai, China
| | - Zhenhua Liu
- Joint Center for Single Cell Biology, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai, China
| | - Guy Polturak
- John Innes Centre, Norwich Research Park, Norwich, UK
| | | | - Lionel Hill
- John Innes Centre, Norwich Research Park, Norwich, UK
| | - Graham Moore
- John Innes Centre, Norwich Research Park, Norwich, UK
| | - Rachel Melton
- John Innes Centre, Norwich Research Park, Norwich, UK
| | - Neil Hall
- Earlham Institute, Norwich Research Park, Norwich, UK
| | | | - Jaroslav Doležel
- Institute of Experimental Botany of the Czech Academy of Sciences, Centre of the Region Haná for Biotechnological and Agricultural Research, Olomouc, Czech Republic
| | - Tim Langdon
- Institute of Biological, Environmental and Rural Sciences, Aberystwyth University, Gogerddan, Aberystwyth, Ceredigion, SY23 3EE, UK
| | - Bin Han
- National Centre for Gene Research, CAS-JIC Centre of Excellence for Plant and Microbial Science (CEPAMS), Centre of Excellence for Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences (CAS), Shanghai, China.
| | - Anne Osbourn
- John Innes Centre, Norwich Research Park, Norwich, UK.
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6
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Kim C, Sung S, Kim J, Lee J. Repair and Reconstruction of Telomeric and Subtelomeric Regions and Genesis of New Telomeres: Implications for Chromosome Evolution. Bioessays 2020; 42:e1900177. [PMID: 32236965 DOI: 10.1002/bies.201900177] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2019] [Revised: 02/20/2020] [Indexed: 12/12/2022]
Abstract
DNA damage repair within telomeres are suppressed to maintain the integrity of linear chromosomes, but the accidental activation of repairs can lead to genome instability. This review develops the concept that mechanisms to repair DNA damage in telomeres contribute to genetic variability and karyotype evolution, rather than catastrophe. Spontaneous breaks in telomeres can be repaired by telomerase, but in some cases DNA repair pathways are activated, and can cause chromosomal rearrangements or fusions. The resultant changes can also affect subtelomeric regions that are adjacent to telomeres. Subtelomeres are actively involved in such chromosomal changes, and are therefore the most variable regions in the genome. The case of Caenorhabditis elegans in the context of changes of subtelomeric structures revealed by long-read sequencing is also discussed. Theoretical and methodological issues covered in this review will help to explore the mechanism of chromosome evolution by reconstruction of chromosomal ends in nature.
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Affiliation(s)
- Chuna Kim
- Department of Biological Sciences, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul, 08827, Korea.,Aging Research Institute, Korea Research Institute of Bioscience and Biotechnology, Gwahak-ro 125, Daejeon, 34141, Korea
| | - Sanghyun Sung
- Department of Biological Sciences, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul, 08827, Korea
| | - Jun Kim
- Department of Biological Sciences, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul, 08827, Korea
| | - Junho Lee
- Department of Biological Sciences, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul, 08827, Korea
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7
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Saha A, Nanavaty VP, Li B. Telomere and Subtelomere R-loops and Antigenic Variation in Trypanosomes. J Mol Biol 2019; 432:4167-4185. [PMID: 31682833 DOI: 10.1016/j.jmb.2019.10.025] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2019] [Revised: 10/02/2019] [Accepted: 10/21/2019] [Indexed: 12/12/2022]
Abstract
Trypanosoma brucei is a kinetoplastid parasite that causes African trypanosomiasis, which is fatal if left untreated. T. brucei regularly switches its major surface antigen, VSG, to evade the host immune responses. VSGs are exclusively expressed from subtelomeric expression sites (ESs) where VSG genes are flanked by upstream 70 bp repeats and downstream telomeric repeats. The telomere downstream of the active VSG is transcribed into a long-noncoding RNA (TERRA), which forms RNA:DNA hybrids (R-loops) with the telomeric DNA. At an elevated level, telomere R-loops cause more telomeric and subtelomeric double-strand breaks (DSBs) and increase VSG switching rate. In addition, stabilized R-loops are observed at the 70 bp repeats and immediately downstream of ES-linked VSGs in RNase H defective cells, which also have an increased amount of subtelomeric DSBs and more frequent VSG switching. Although subtelomere plasticity is expected to be beneficial to antigenic variation, severe defects in subtelomere integrity and stability increase cell lethality. Therefore, regulation of the telomere and 70 bp repeat R-loop levels is important for the balance between antigenic variation and cell fitness in T. brucei. In addition, the high level of the active ES transcription favors accumulation of R-loops at the telomere and 70 bp repeats, providing an intrinsic mechanism for local DSB formation, which is a strong inducer of VSG switching.
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Affiliation(s)
- Arpita Saha
- Center for Gene Regulation in Health and Disease, Department of Biological, Geological, and Environmental Sciences, College of Science and Health Professions, Cleveland State University, 2121 Euclid Avenue, Cleveland, OH 44115, USA
| | - Vishal P Nanavaty
- Center for Gene Regulation in Health and Disease, Department of Biological, Geological, and Environmental Sciences, College of Science and Health Professions, Cleveland State University, 2121 Euclid Avenue, Cleveland, OH 44115, USA
| | - Bibo Li
- Center for Gene Regulation in Health and Disease, Department of Biological, Geological, and Environmental Sciences, College of Science and Health Professions, Cleveland State University, 2121 Euclid Avenue, Cleveland, OH 44115, USA; Case Comprehensive Cancer Center, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA; Department of Inflammation and Immunity, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA.
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8
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Bhandari J, Karg T, Golic KG. Homolog-Dependent Repair Following Dicentric Chromosome Breakage in Drosophila melanogaster. Genetics 2019; 212:615-630. [PMID: 31053594 PMCID: PMC6614899 DOI: 10.1534/genetics.119.302247] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Accepted: 04/29/2019] [Indexed: 12/11/2022] Open
Abstract
Double-strand DNA breaks are repaired by one of several mechanisms that rejoin two broken ends. However, cells are challenged when asked to repair a single broken end and respond by: (1) inducing programmed cell death; (2) healing the broken end by constructing a new telomere; (3) adapting to the broken end and resuming the mitotic cycle without repair; and (4) using information from the sister chromatid or homologous chromosome to restore a normal chromosome terminus. During one form of homolog-dependent repair in yeast, termed break-induced replication (BIR), a template chromosome can be copied for hundreds of kilobases. BIR efficiency depends on Pif1 helicase and Pol32, a nonessential subunit of DNA polymerase δ. To date, there is little evidence that BIR can be used for extensive chromosome repair in higher eukaryotes. We report that a dicentric chromosome broken in mitosis in the male germline of Drosophila melanogaster is usually repaired by healing, but can also be repaired in a homolog-dependent fashion, restoring at least 1.3 Mb of terminal sequence information. This mode of repair is significantly reduced in pif1 and pol32 mutants. Formally, the repaired chromosomes are recombinants. However, the absence of reciprocal recombinants and the dependence on Pif1 and Pol32 strongly support the hypothesis that BIR is the mechanism for restoration of the chromosome terminus. In contrast to yeast, pif1 mutants in Drosophila exhibit a reduced rate of chromosome healing, likely owing to fundamental differences in telomeres between these organisms.
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Affiliation(s)
- Jayaram Bhandari
- School of Biological Sciences, University of Utah, Salt Lake City, Utah 84112
| | - Travis Karg
- School of Biological Sciences, University of Utah, Salt Lake City, Utah 84112
| | - Kent G Golic
- School of Biological Sciences, University of Utah, Salt Lake City, Utah 84112
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9
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Fillinger RJ, Anderson MZ. Seasons of change: Mechanisms of genome evolution in human fungal pathogens. INFECTION, GENETICS AND EVOLUTION : JOURNAL OF MOLECULAR EPIDEMIOLOGY AND EVOLUTIONARY GENETICS IN INFECTIOUS DISEASES 2019; 70:165-174. [PMID: 30826447 DOI: 10.1016/j.meegid.2019.02.031] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Revised: 02/23/2019] [Accepted: 02/26/2019] [Indexed: 06/09/2023]
Abstract
Fungi are a diverse kingdom of organisms capable of thriving in various niches across the world including those in close association with multicellular eukaryotes. Fungal pathogens that contribute to human disease reside both within the host as commensal organisms of the microbiota and the environment. Their niche of origin dictates how infection initiates but also places specific selective pressures on the fungal pathogen that contributes to its genome organization and genetic repertoire. Recent efforts to catalogue genomic variation among major human fungal pathogens have unveiled evolutionary themes that shape the fungal genome. Mechanisms ranging from large scale changes such as aneuploidy and ploidy cycling as well as more targeted mutations like base substitutions and gene copy number variations contribute to the evolution of these species, which are often under multiple competing selective pressures with their host, environment, and other microbes. Here, we provide an overview of the major selective pressures and mechanisms acting to evolve the genome of clinically important fungal pathogens of humans.
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Affiliation(s)
- Robert J Fillinger
- Department of Microbial Infection and Immunity, The Ohio State University, Columbus, OH 43210, USA
| | - Matthew Z Anderson
- Department of Microbial Infection and Immunity, The Ohio State University, Columbus, OH 43210, USA; Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA.
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10
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Zhang X, Alexander N, Leonardi I, Mason C, Kirkman LA, Deitsch KW. Rapid antigen diversification through mitotic recombination in the human malaria parasite Plasmodium falciparum. PLoS Biol 2019; 17:e3000271. [PMID: 31083650 PMCID: PMC6532940 DOI: 10.1371/journal.pbio.3000271] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Revised: 05/23/2019] [Accepted: 04/30/2019] [Indexed: 11/18/2022] Open
Abstract
Malaria parasites possess the remarkable ability to maintain chronic infections that fail to elicit a protective immune response, characteristics that have stymied vaccine development and cause people living in endemic regions to remain at risk of malaria despite previous exposure to the disease. These traits stem from the tremendous antigenic diversity displayed by parasites circulating in the field. For Plasmodium falciparum, the most virulent of the human malaria parasites, this diversity is exemplified by the variant gene family called var, which encodes the major surface antigen displayed on infected red blood cells (RBCs). This gene family exhibits virtually limitless diversity when var gene repertoires from different parasite isolates are compared. Previous studies indicated that this remarkable genome plasticity results from extensive ectopic recombination between var genes during mitotic replication; however, the molecular mechanisms that direct this process to antigen-encoding loci while the rest of the genome remains relatively stable were not determined. Using targeted DNA double-strand breaks (DSBs) and long-read whole-genome sequencing, we show that a single break within an antigen-encoding region of the genome can result in a cascade of recombination events leading to the generation of multiple chimeric var genes, a process that can greatly accelerate the generation of diversity within this family. We also found that recombinations did not occur randomly, but rather high-probability, specific recombination products were observed repeatedly. These results provide a molecular basis for previously described structured rearrangements that drive diversification of this highly polymorphic gene family.
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Affiliation(s)
- Xu Zhang
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York, United States of America
| | - Noah Alexander
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, New York, United States of America
| | - Irina Leonardi
- Jill Roberts Center for Inflammatory Bowel Disease, Weill Cornell Medical College, New York, New York, United States of America
| | - Christopher Mason
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, New York, United States of America
- HRH Prince Alwaleed Bin Talal Bin Abdulaziz Alsaud Institute for Computational Biomedicine, Weill Cornell Medical College, New York, New York, United States of America
- Feil Family Brain and Mind Research Institute, Weill Cornell Medical College, New York, New York, United States of America
- WorldQuant Initiative for Quantitative Prediction, Weill Cornell Medical College, New York, New York, United States of America
| | - Laura A. Kirkman
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York, United States of America
- Department of Internal Medicine, Division of Infectious Diseases, Weill Cornell Medical College, New York, New York, United States of America
| | - Kirk W. Deitsch
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York, United States of America
- * E-mail:
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Lauer S, Gresham D. An evolving view of copy number variants. Curr Genet 2019; 65:1287-1295. [PMID: 31076843 DOI: 10.1007/s00294-019-00980-0] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Revised: 04/17/2019] [Accepted: 04/20/2019] [Indexed: 01/08/2023]
Abstract
Copy number variants (CNVs) are regions of the genome that vary in integer copy number. CNVs, which comprise both amplifications and deletions of DNA sequence, have been identified across all domains of life, from bacteria and archaea to plants and animals. CNVs are an important source of genetic diversity, and can drive rapid adaptive evolution and progression of heritable and somatic human diseases, such as cancer. However, despite their evolutionary importance and clinical relevance, CNVs remain understudied compared to single-nucleotide variants (SNVs). This is a consequence of the inherent difficulties in detecting CNVs at low-to-intermediate frequencies in heterogeneous populations of cells. Here, we discuss molecular methods used to detect CNVs, the limitations associated with using these techniques, and the application of new and emerging technologies that present solutions to these challenges. The goal of this short review and perspective is to highlight aspects of CNV biology that are understudied and define avenues for further research that address specific gaps in our knowledge of these complex alleles. We describe our recently developed method for CNV detection in which a fluorescent gene functions as a single-cell CNV reporter and present key findings from our evolution experiments in Saccharomyces cerevisiae. Using a CNV reporter, we found that CNVs are generated at a high rate and undergo selection with predictable dynamics across independently evolving replicate populations. Many CNVs appear to be generated through DNA replication-based processes that are mediated by the presence of short, interrupted, inverted-repeat sequences. Our results have important implications for the role of CNVs in evolutionary processes and the molecular mechanisms that underlie CNV formation. We discuss the possible extension of our method to other applications, including tracking the dynamics of CNVs in models of human tumors.
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Affiliation(s)
- Stephanie Lauer
- Institute for Systems Genetics, New York University Langone Health, New York, NY, USA
| | - David Gresham
- Center for Genomics and System Biology, Department of Biology, New York University, New York, NY, USA.
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TASks for subtelomeres: when nucleosome loss and genome instability are favored. Curr Genet 2019; 65:1153-1160. [DOI: 10.1007/s00294-019-00986-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 04/29/2019] [Accepted: 04/30/2019] [Indexed: 10/26/2022]
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13
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Botcinic acid biosynthesis in Botrytis cinerea relies on a subtelomeric gene cluster surrounded by relics of transposons and is regulated by the Zn2Cys6 transcription factor BcBoa13. Curr Genet 2019; 65:965-980. [DOI: 10.1007/s00294-019-00952-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Revised: 02/26/2019] [Accepted: 03/02/2019] [Indexed: 01/11/2023]
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14
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Role of Mediator in virulence and antifungal drug resistance in pathogenic fungi. Curr Genet 2019; 65:621-630. [DOI: 10.1007/s00294-019-00932-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Revised: 01/04/2019] [Accepted: 01/05/2019] [Indexed: 10/27/2022]
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15
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Juárez-Reyes A, Castaño I. Chromatin architecture and virulence-related gene expression in eukaryotic microbial pathogens. Curr Genet 2018; 65:435-443. [PMID: 30443783 DOI: 10.1007/s00294-018-0903-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Revised: 10/30/2018] [Accepted: 11/10/2018] [Indexed: 12/19/2022]
Abstract
A fundamental question in biology is to understand how appropriate transcriptional regulation and dense packaging of the genetic material within the eukaryotic nucleus are achieved. The exquisite gene expression control and other metabolic processes of DNA require a highly complex, multilayered, three-dimensional architecture of the chromatin and its specific compartmentalization within the nucleus. Some of these architectural and sub-nuclear positioning mechanisms have been extensively co-opted by eukaryotic pathogens to keep fine expression control and expansion of virulence-related gene families in Plasmodium falciparum, Trypanosoma brucei and Candida glabrata. For example non-linear interactions between distant cis-acting regions and the formation of chromatin loops are required for appropriate regulation of the expression of virulence-related multi-gene families encoding cell surface proteins. These gene families are located near the chromosome ends and tethered to the nuclear periphery. Consequently, only one or very few genes of the family are expressed at a time. These genes are involved in antigenic variation in parasites and the generation of subpopulations of cells with diverse antigenic proteins at the surface in some pathogenic fungi, making them highly efficient pathogens.
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Affiliation(s)
- Alejandro Juárez-Reyes
- División de Biología Molecular, IPICYT, Instituto Potosino de Investigación Científica y Tecnológica, Camino a la Presa San José 2055, 78216, San Luis Potosí, SLP, Mexico
| | - Irene Castaño
- División de Biología Molecular, IPICYT, Instituto Potosino de Investigación Científica y Tecnológica, Camino a la Presa San José 2055, 78216, San Luis Potosí, SLP, Mexico.
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