1
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Impact of alternative splicing on mechanisms of resistance to anticancer drugs. Biochem Pharmacol 2021; 193:114810. [PMID: 34673012 DOI: 10.1016/j.bcp.2021.114810] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 10/05/2021] [Accepted: 10/06/2021] [Indexed: 12/15/2022]
Abstract
A shared characteristic of many tumors is the lack of response to anticancer drugs. Multiple mechanisms of pharmacoresistance (MPRs) are involved in permitting cancer cells to overcome the effect of these agents. Pharmacoresistance can be primary (intrinsic) or secondary (acquired), i.e., triggered or enhanced in response to the treatment. Moreover, MPRs usually result in the lack of sensitivity to several agents, which accounts for diverse multidrug-resistant (MDR) phenotypes. MPRs are based on the dynamic expression of more than one hundred genes, constituting the so-called resistome. Alternative splicing (AS) during pre-mRNA maturation results in changes affecting proteins involved in the resistome. The resulting splicing variants (SVs) reduce the efficacy of anticancer drugs by lowering the intracellular levels of active agents, altering molecular targets, enhancing both DNA repair ability and defensive mechanism of tumors, inducing changes in the balance between pro-survival and pro-apoptosis signals, modifying interactions with the tumor microenvironment, and favoring malignant phenotypic transitions. Reasons accounting for cancer-associated aberrant splicing include mutations that create or disrupt splicing sites or splicing enhancers or silencers, abnormal expression of splicing factors, and impaired signaling pathways affecting the activity of the splicing machinery. Here we have reviewed the impact of AS on MPR in cancer cells.
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2
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Mayers CG, Harrington TC, Wai A, Hausner G. Recent and Ongoing Horizontal Transfer of Mitochondrial Introns Between Two Fungal Tree Pathogens. Front Microbiol 2021; 12:656609. [PMID: 34149643 PMCID: PMC8208691 DOI: 10.3389/fmicb.2021.656609] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Accepted: 04/09/2021] [Indexed: 11/23/2022] Open
Abstract
Two recently introduced fungal plant pathogens (Ceratocystis lukuohia and Ceratocystis huliohia) are responsible for Rapid ‘ōhi‘a Death (ROD) in Hawai‘i. Despite being sexually incompatible, the two pathogens often co-occur in diseased ‘ōhi‘a sapwood, where genetic interaction is possible. We sequenced and annotated 33 mitochondrial genomes of the two pathogens and related species, and investigated 35 total Ceratocystis mitogenomes. Ten mtDNA regions [one group I intron, seven group II introns, and two autonomous homing endonuclease (HE) genes] were heterogeneously present in C. lukuohia mitogenomes, which were otherwise identical. Molecular surveys with specific primers showed that the 10 regions had uneven geographic distribution amongst populations of C. lukuohia. Conversely, identical orthologs of each region were present in every studied isolate of C. huliohia regardless of geographical origin. Close relatives of C. lukuohia lacked or, rarely, had few and dissimilar orthologs of the 10 regions, whereas most relatives of C. huliohia had identical or nearly identical orthologs. Each region included or worked in tandem with HE genes or reverse transcriptase/maturases that could facilitate interspecific horizontal transfers from intron-minus to intron-plus alleles. These results suggest that the 10 regions originated in C. huliohia and are actively moving to populations of C. lukuohia, perhaps through transient cytoplasmic contact of hyphal tips (anastomosis) in the wound surface of ‘ōhi‘a trees. Such contact would allow for the transfer of mitochondria followed by mitochondrial fusion or cytoplasmic exchange of intron intermediaries, which suggests that further genomic interaction may also exist between the two pathogens.
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Affiliation(s)
- Chase G Mayers
- Department of Plant Pathology and Microbiology, Iowa State University, Ames, IA, United States
| | - Thomas C Harrington
- Department of Plant Pathology and Microbiology, Iowa State University, Ames, IA, United States
| | - Alvan Wai
- Department of Microbiology, University of Manitoba, Winnipeg, MB, Canada
| | - Georg Hausner
- Department of Microbiology, University of Manitoba, Winnipeg, MB, Canada
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3
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Zhang C, Ma H, Sanchez-Puerta MV, Li L, Xiao J, Liu Z, Ci X, Li J. Horizontal Gene Transfer has Impacted cox1 Gene Evolution in Cassytha filiformis. J Mol Evol 2020; 88:361-371. [DOI: 10.1007/s00239-020-09937-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Accepted: 03/06/2020] [Indexed: 11/30/2022]
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4
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Fan WW, Zhang S, Zhang YJ. The complete mitochondrial genome of the Chan-hua fungus Isaria cicadae: a tale of intron evolution in Cordycipitaceae. Environ Microbiol 2019; 21:864-879. [PMID: 30623556 DOI: 10.1111/1462-2920.14522] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Revised: 01/04/2019] [Accepted: 01/05/2019] [Indexed: 11/30/2022]
Abstract
Isaria cicadae is an entomogenous fungus of great medicinal value. Its nuclear genome has been reported, while its mitogenome remains unknown. Herein, we first described its mitogenome and then inferred intron evolution from both intraspecific and interspecific perspectives. The fungus represented the largest mitogenome (56.6 kb in strain CCAD02) known in Cordycipitaceae due to the presence of 25 introns interrupting nine genes. Comparison of three I. cicadae strains revealed intron presence/absence dynamics at six intron loci plus a few indels and single nucleotide polymorphisms. Phylogenetic analyses confirmed the placement of I. cicadae in Cordycipitaceae. Comparison of 10 Cordycipitaceae species revealed a high degree of synteny and conserved genetic content. They, however, varied in intron numbers (1-25 per species) with overall 34 intron loci identified, which resulted in more than twofold variations in mitogenome sizes (24.5-56.6 kb). An rnl intron encoding ribosomal protein S3 was present in all species, suggesting its early invasion in Cordycipitaceae, while further divergence occurred for this intron. The other introns identified in this study were present in some, but not all of the species and have undergone multiple gains and losses in Cordycipitaceae. This study greatly enhanced our understanding of intron evolution in Cordycipitaceae.
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Affiliation(s)
- Wen-Wen Fan
- School of Life Science, Shanxi University, Taiyuan 030006, China.,Institute of Biotechnology, Shanxi University, Taiyuan 030006, China
| | - Shu Zhang
- Institute of Applied Chemistry, Shanxi University, Taiyuan 030006, China
| | - Yong-Jie Zhang
- School of Life Science, Shanxi University, Taiyuan 030006, China
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Zhao L, Rosario K, Breitbart M, Duffy S. Eukaryotic Circular Rep-Encoding Single-Stranded DNA (CRESS DNA) Viruses: Ubiquitous Viruses With Small Genomes and a Diverse Host Range. Adv Virus Res 2018; 103:71-133. [PMID: 30635078 DOI: 10.1016/bs.aivir.2018.10.001] [Citation(s) in RCA: 123] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
While single-stranded DNA (ssDNA) was once thought to be a relatively rare genomic architecture for viruses, modern metagenomics sequencing has revealed circular ssDNA viruses in most environments and in association with diverse hosts. In particular, circular ssDNA viruses encoding a homologous replication-associated protein (Rep) have been identified in the majority of eukaryotic supergroups, generating interest in the ecological effects and evolutionary history of circular Rep-encoding ssDNA viruses (CRESS DNA) viruses. This review surveys the explosion of sequence diversity and expansion of eukaryotic CRESS DNA taxonomic groups over the last decade, highlights similarities between the well-studied geminiviruses and circoviruses with newly identified groups known only through their genome sequences, discusses the ecology and evolution of eukaryotic CRESS DNA viruses, and speculates on future research horizons.
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Affiliation(s)
- Lele Zhao
- Department of Ecology, Evolution and Natural Resources, Rutgers, the State University of New Jersey, New Brunswick, NJ, United States
| | - Karyna Rosario
- College of Marine Science, University of South Florida, Saint Petersburg, FL, United States
| | - Mya Breitbart
- College of Marine Science, University of South Florida, Saint Petersburg, FL, United States
| | - Siobain Duffy
- Department of Ecology, Evolution and Natural Resources, Rutgers, the State University of New Jersey, New Brunswick, NJ, United States.
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6
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Wang L, Zhang S, Li JH, Zhang YJ. Mitochondrial genome, comparative analysis and evolutionary insights into the entomopathogenic fungusHirsutella thompsonii. Environ Microbiol 2018; 20:3393-3405. [DOI: 10.1111/1462-2920.14379] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 08/08/2018] [Accepted: 08/09/2018] [Indexed: 12/19/2022]
Affiliation(s)
- Lin Wang
- School of Life Science; Shanxi University; Taiyuan 030006 China
- Institute of Biotechnology; Shanxi University; Taiyuan 030006 China
| | - Shu Zhang
- Institute of Applied Chemistry; Shanxi University; Taiyuan 030006 China
| | - Jian-Hui Li
- College of Animal Science and Veterinary Medicine; Shanxi Agricultural University; Taigu 030801 China
| | - Yong-Jie Zhang
- School of Life Science; Shanxi University; Taiyuan 030006 China
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Yan Z, Li Z, Yan L, Yu Y, Cheng Y, Chen J, Liu Y, Gao C, Zeng L, Sun X, Guo L, Xu J. Deletion of the sex-determining gene SXI1α enhances the spread of mitochondrial introns in Cryptococcus neoformans. Mob DNA 2018; 9:24. [PMID: 30026817 PMCID: PMC6048814 DOI: 10.1186/s13100-018-0129-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Accepted: 07/10/2018] [Indexed: 01/19/2023] Open
Abstract
Background Homing endonuclease genes (HEGs) are widely distributed genetic elements in the mitochondrial genomes of a diversity of eukaryotes. Due to their ability to self-propagate within and between genomes, these elements can spread rapidly in populations. Whether and how such elements are controlled in genomes remains largely unknown. Results Here we report that the HEG-containing introns in the mitochondrial COX1 gene in Cryptococcus neoformans are mobile and that their spread in sexual crosses is influenced by mating type (MAT) α-specific homeodomain gene SXI1α. C. neoformans has two mating types, MATa and MATα. In typical crosses between strains of the two mating types, only a small portion (< 7%) of diploid fusants inherited the HEGs from the MATα parent. However, disruption of the SXI1α gene resulted in the majority (> 95%) of the diploid fusants inheriting the HEG-containing introns from the MATα parent, a frequency significantly higher than those of intronless mitochondrial genes. Conclusions Our results suggest that SXI1α not only determines uniparental mitochondrial inheritance but also inhibits the spread of HEG-containing introns in the mitochondrial genome in C. neoformans.
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Affiliation(s)
- Zhun Yan
- 1Institute of Bast Fiber Crops, Chinese Academy of Agricultural Sciences, Changsha, 410205 Hunan China
| | - Zhimin Li
- 1Institute of Bast Fiber Crops, Chinese Academy of Agricultural Sciences, Changsha, 410205 Hunan China
| | - Li Yan
- 1Institute of Bast Fiber Crops, Chinese Academy of Agricultural Sciences, Changsha, 410205 Hunan China
| | - Yongting Yu
- 1Institute of Bast Fiber Crops, Chinese Academy of Agricultural Sciences, Changsha, 410205 Hunan China
| | - Yi Cheng
- 1Institute of Bast Fiber Crops, Chinese Academy of Agricultural Sciences, Changsha, 410205 Hunan China
| | - Jia Chen
- 1Institute of Bast Fiber Crops, Chinese Academy of Agricultural Sciences, Changsha, 410205 Hunan China
| | - Yunyun Liu
- 1Institute of Bast Fiber Crops, Chinese Academy of Agricultural Sciences, Changsha, 410205 Hunan China
| | - Chunsheng Gao
- 1Institute of Bast Fiber Crops, Chinese Academy of Agricultural Sciences, Changsha, 410205 Hunan China
| | - Liangbin Zeng
- 1Institute of Bast Fiber Crops, Chinese Academy of Agricultural Sciences, Changsha, 410205 Hunan China
| | - Xiangping Sun
- 1Institute of Bast Fiber Crops, Chinese Academy of Agricultural Sciences, Changsha, 410205 Hunan China
| | - Litao Guo
- 1Institute of Bast Fiber Crops, Chinese Academy of Agricultural Sciences, Changsha, 410205 Hunan China
| | - Jianping Xu
- 2Department of Biology, McMaster University, Hamilton, ON L8S 4K1 Canada
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Gomes FEES, Arantes TD, Fernandes JAL, Ferreira LC, Romero H, Bosco SMG, Oliveira MTB, Del Negro GMB, Theodoro RC. Polymorphism in Mitochondrial Group I Introns among Cryptococcus neoformans and Cryptococcus gattii Genotypes and Its Association with Drug Susceptibility. Front Microbiol 2018; 9:86. [PMID: 29467729 PMCID: PMC5808193 DOI: 10.3389/fmicb.2018.00086] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Accepted: 01/12/2018] [Indexed: 12/21/2022] Open
Abstract
Cryptococcosis, one of the most important systemic mycosis in the world, is caused by different genotypes of Cryptococcus neoformans and Cryptococcus gattii, which differ in their ecology, epidemiology, and antifungal susceptibility. Therefore, the search for new molecular markers for genotyping, pathogenicity and drug susceptibility is necessary. Group I introns fulfill the requisites for such task because (i) they are polymorphic sequences; (ii) their self-splicing is inhibited by some drugs; and (iii) their correct splicing under parasitic conditions is indispensable for pathogen survival. Here, we investigated the presence of group I introns in the mitochondrial LSU rRNA gene in 77 Cryptococcus isolates and its possible relation to drug susceptibility. Sequencing revealed two new introns in the LSU rRNA gene. All the introns showed high sequence similarity to other mitochondrial introns from distinct fungi, supporting the hypothesis of an ancient non-allelic invasion. Intron presence was statistically associated with those genotypes reported to be less pathogenic (p < 0.001). Further virulence assays are needed to confirm this finding. In addition, in vitro antifungal tests indicated that the presence of LSU rRNA introns may influence the minimum inhibitory concentration (MIC) of amphotericin B and 5-fluorocytosine. These findings point to group I introns in the mitochondrial genome of Cryptococcus as potential molecular markers for antifungal resistance, as well as therapeutic targets.
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Affiliation(s)
- Felipe E. E. S. Gomes
- Department of Biochemistry, Universidade Federal do Rio Grande do Norte, Natal, Brazil
- Institute of Tropical Medicine of Rio Grande do Norte, Universidade Federal do Rio Grande do Norte, Natal, Brazil
| | - Thales D. Arantes
- Department of Biochemistry, Universidade Federal do Rio Grande do Norte, Natal, Brazil
- Institute of Tropical Medicine of Rio Grande do Norte, Universidade Federal do Rio Grande do Norte, Natal, Brazil
| | - José A. L. Fernandes
- Institute of Tropical Medicine of Rio Grande do Norte, Universidade Federal do Rio Grande do Norte, Natal, Brazil
| | - Leonardo C. Ferreira
- Department of Biochemistry, Universidade Federal do Rio Grande do Norte, Natal, Brazil
- Institute of Tropical Medicine of Rio Grande do Norte, Universidade Federal do Rio Grande do Norte, Natal, Brazil
| | - Héctor Romero
- Laboratorio de Organizacion y Evolución del Genoma/Unidad de Genómica Evolutiva, Departamento de Ecología y Evolución, Facultad de Ciencias/CURE, Universidad de la República, Maldonado, Uruguay
| | - Sandra M. G. Bosco
- Department of Microbiology and Immunology, Institute of Biosciences, Universidade Estadual Paulista Julio de Mesquita Filho, São Paulo, Brazil
| | - Maria T. B. Oliveira
- Department of Microbiology and Parasitology, Universidade Federal do Rio Grande do Norte, Natal, Brazil
| | - Gilda M. B. Del Negro
- Institute of Tropical Medicine of São Paulo, Universidade de São Paulo, São Paulo, Brazil
| | - Raquel C. Theodoro
- Institute of Tropical Medicine of Rio Grande do Norte, Universidade Federal do Rio Grande do Norte, Natal, Brazil
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Sokolov AS, Latypov OR, Kolosov PM, Shlyapnikov MG, Bezlepkina TA, Kholod NS, Kadyrov FA, Granovsky IE. Phage T4 endonuclease SegD that is similar to group I intron endonucleases does not initiate homing of its own gene. Virology 2018; 515:215-222. [PMID: 29306059 DOI: 10.1016/j.virol.2017.12.031] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Revised: 12/25/2017] [Accepted: 12/26/2017] [Indexed: 11/30/2022]
Abstract
Homing endonucleases are a group of site-specific endonucleases that initiate homing, a nonreciprocal transfer of its own gene into a new allele lacking this gene. This work describes a novel phage T4 endonuclease, SegD, which is homologous to the GIY-YIG family of homing endonucleases. Like other T4 homing endonucleases SegD recognizes an extended, 16bp long, site, cleaves it asymmetrically to form 3'-protruding ends and digests both unmodified DNA and modified T-even phage DNA with similar efficiencies. Surprisingly, we revealed that SegD cleavage site was identical in the genomes of segD- and segD+ phages. We found that segD gene was expressed during the T4 developmental cycle. Nevertheless, endonuclease SegD was not able to initiate homing of its own gene as well as genetic recombination between phages in its site inserted into the rII locus.
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Affiliation(s)
- Andrey S Sokolov
- Laboratory of Genetic Enzymology, Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, 5 Prospekt Nauki, Pushchino 142290, Russia
| | - Oleg R Latypov
- Laboratory of Genetic Enzymology, Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, 5 Prospekt Nauki, Pushchino 142290, Russia
| | - Peter M Kolosov
- Laboratory of Genetic Enzymology, Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, 5 Prospekt Nauki, Pushchino 142290, Russia
| | - Michael G Shlyapnikov
- Laboratory of Genetic Enzymology, Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, 5 Prospekt Nauki, Pushchino 142290, Russia
| | - Tamara A Bezlepkina
- Laboratory of Genetic Enzymology, Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, 5 Prospekt Nauki, Pushchino 142290, Russia
| | - Natalia S Kholod
- Laboratory of Genetic Enzymology, Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, 5 Prospekt Nauki, Pushchino 142290, Russia
| | - Farid A Kadyrov
- Laboratory of Genetic Enzymology, Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, 5 Prospekt Nauki, Pushchino 142290, Russia
| | - Igor E Granovsky
- Laboratory of Genetic Enzymology, Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, 5 Prospekt Nauki, Pushchino 142290, Russia; Laboratory of Molecular and Cellular Biology, Pushchino State Institute of Natural Sciences, 3 Prospekt Nauki, Pushchino 142290, Russia.
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Abstract
Self-propagating gene drive technologies have a number of desirable characteristics that warrant their development for the control of insect pest and vector populations, such as the malaria-transmitting mosquitoes. Theoretically easy to deploy and self-sustaining, these tools may be used to generate cost-effective interventions that benefit society without obvious bias related to wealth, age or education. Their species-specific design offers the potential to reduce environmental risks and aim to be compatible and complementary with other control strategies, potentially expediting the elimination and eradication of malaria. A number of strategies have been proposed for gene-drive based control of the malaria mosquito and recent demonstrations have shown proof-of-principle in the laboratory. Though several technical, ethical and regulatory challenges remain, none appear insurmountable if research continues in a step-wise and open manner.
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Affiliation(s)
| | - Roberto Galizi
- Department of Life Sciences, Imperial College London, London, UK
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Zaccaron AZ, Woloshuk CP, Bluhm BH. Comparative genomics of maize ear rot pathogens reveals expansion of carbohydrate-active enzymes and secondary metabolism backbone genes in Stenocarpella maydis. Fungal Biol 2017; 121:966-983. [PMID: 29029703 DOI: 10.1016/j.funbio.2017.08.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Revised: 08/15/2017] [Accepted: 08/18/2017] [Indexed: 12/11/2022]
Abstract
Stenocarpella maydis is a plant pathogenic fungus that causes Diplodia ear rot, one of the most destructive diseases of maize. To date, little information is available regarding the molecular basis of pathogenesis in this organism, in part due to limited genomic resources. In this study, a 54.8 Mb draft genome assembly of S. maydis was obtained with Illumina and PacBio sequencing technologies, and analyzed. Comparative genomic analyses with the predominant maize ear rot pathogens Aspergillus flavus, Fusarium verticillioides, and Fusarium graminearum revealed an expanded set of carbohydrate-active enzymes for cellulose and hemicellulose degradation in S. maydis. Analyses of predicted genes involved in starch degradation revealed six putative α-amylases, four extracellular and two intracellular, and two putative γ-amylases, one of which appears to have been acquired from bacteria via horizontal transfer. Additionally, 87 backbone genes involved in secondary metabolism were identified, which represents one of the largest known assemblages among Pezizomycotina species. Numerous secondary metabolite gene clusters were identified, including two clusters likely involved in the biosynthesis of diplodiatoxin and chaetoglobosins. The draft genome of S. maydis presented here will serve as a useful resource for molecular genetics, functional genomics, and analyses of population diversity in this organism.
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Affiliation(s)
- Alex Z Zaccaron
- Department of Plant Pathology, University of Arkansas, Division of Agriculture, Fayetteville, AR 72701, USA
| | - Charles P Woloshuk
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN, USA
| | - Burton H Bluhm
- Department of Plant Pathology, University of Arkansas, Division of Agriculture, Fayetteville, AR 72701, USA.
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Schuster A, Lopez JV, Becking LE, Kelly M, Pomponi SA, Wörheide G, Erpenbeck D, Cárdenas P. Evolution of group I introns in Porifera: new evidence for intron mobility and implications for DNA barcoding. BMC Evol Biol 2017; 17:82. [PMID: 28320321 PMCID: PMC5360047 DOI: 10.1186/s12862-017-0928-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Accepted: 02/28/2017] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND Mitochondrial introns intermit coding regions of genes and feature characteristic secondary structures and splicing mechanisms. In metazoans, mitochondrial introns have only been detected in sponges, cnidarians, placozoans and one annelid species. Within demosponges, group I and group II introns are present in six families. Based on different insertion sites within the cox1 gene and secondary structures, four types of group I and two types of group II introns are known, which can harbor up to three encoding homing endonuclease genes (HEG) of the LAGLIDADG family (group I) and/or reverse transcriptase (group II). However, only little is known about sponge intron mobility, transmission, and origin due to the lack of a comprehensive dataset. We analyzed the largest dataset on sponge mitochondrial group I introns to date: 95 specimens, from 11 different sponge genera which provided novel insights into the evolution of group I introns. RESULTS For the first time group I introns were detected in four genera of the sponge family Scleritodermidae (Scleritoderma, Microscleroderma, Aciculites, Setidium). We demonstrated that group I introns in sponges aggregate in the most conserved regions of cox1. We showed that co-occurrence of two introns in cox1 is unique among metazoans, but not uncommon in sponges. However, this combination always associates an active intron with a degenerating one. Earlier hypotheses of HGT were confirmed and for the first time VGT and secondary losses of introns conclusively demonstrated. CONCLUSION This study validates the subclass Spirophorina (Tetractinellida) as an intron hotspot in sponges. Our analyses confirm that most sponge group I introns probably originated from fungi. DNA barcoding is discussed and the application of alternative primers suggested.
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Affiliation(s)
- Astrid Schuster
- Department of Earth- & Environmental Sciences, Palaeontology and Geobiology, Ludwig-Maximilians-Universität München, Richard-Wagner-Str. 10, 80333 Munich, Germany
| | - Jose V. Lopez
- Halmos College of Natural Sciences and Oceanography, Nova Southeastern University, Dania Beach, FL 33004 USA
| | - Leontine E. Becking
- Marine Animal Ecology, Wageningen University & Research Centre, P.O. Box 3700, AH, Wageningen, The Netherlands
- Naturalis Biodiversity Center, Marine Zoology Department, PO Box 9517, 2300 RA, Leiden, The Netherlands
| | - Michelle Kelly
- National Centre for Aquatic Biodiversity and Biosecurity, National Institute of Water and Atmospheric Research, P.O. Box 109–695, Newmarket, Auckland, New Zealand
| | - Shirley A. Pomponi
- Harbor Branch Oceanographic Institute-Florida Atlantic University, 5600 U.S. 1 North, Ft Pierce, FL 34946 USA
| | - Gert Wörheide
- Department of Earth- & Environmental Sciences, Palaeontology and Geobiology, Ludwig-Maximilians-Universität München, Richard-Wagner-Str. 10, 80333 Munich, Germany
- SNSB - Bavarian State Collections of Palaeontology and Geology, Richard-Wagner Str. 10, 80333 Munich, Germany
- GeoBio-CenterLMU, Ludwig-Maximilians-Universität München, Richard-Wagner Str. 10, 80333 Munich, Germany
| | - Dirk Erpenbeck
- Department of Earth- & Environmental Sciences, Palaeontology and Geobiology, Ludwig-Maximilians-Universität München, Richard-Wagner-Str. 10, 80333 Munich, Germany
- GeoBio-CenterLMU, Ludwig-Maximilians-Universität München, Richard-Wagner Str. 10, 80333 Munich, Germany
| | - Paco Cárdenas
- Department of Medicinal Chemistry, Division of Pharmacognosy, BioMedical Center, Uppsala University, Husargatan 3, 75123 Uppsala, Sweden
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Ruck EC, Linard SR, Nakov T, Theriot EC, Alverson AJ. Hoarding and horizontal transfer led to an expanded gene and intron repertoire in the plastid genome of the diatom, Toxarium undulatum (Bacillariophyta). Curr Genet 2016; 63:499-507. [PMID: 27655214 DOI: 10.1007/s00294-016-0652-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 09/12/2016] [Accepted: 09/16/2016] [Indexed: 11/25/2022]
Abstract
Although the plastid genomes of diatoms maintain a conserved architecture and core gene set, considerable variation about this core theme exists and can be traced to several different processes. Gene duplication, pseudogenization, and loss, as well as intracellular transfer of genes to the nuclear genome, have all contributed to variation in gene content among diatom species. In addition, some noncoding sequences have highly restricted phylogenetic distributions that suggest a recent foreign origin. We sequenced the plastid genome of the marine diatom, Toxarium undulatum, and found that the genome contains three genes (chlB, chlL, and chlN) involved in light-independent chlorophyll a biosynthesis that were not previously known from diatoms. Phylogenetic and syntenic data suggest that these genes were differentially retained in this one lineage as they were repeatedly lost from most other diatoms. Unique among diatoms and other heterokont algae sequenced so far, the genome also contains a large group II intron within an otherwise intact psaA gene. Although the intron is most similar to one in the plastid-encoded psaA gene of some green algae, high sequence divergence between the diatom and green algal introns rules out recent shared ancestry. We conclude that the psaA intron was likely introduced into the plastid genome of T. undulatum, or some earlier ancestor, by horizontal transfer from an unknown donor. This genome further highlights the myriad processes driving variation in gene and intron content in the plastid genomes of diatoms, one of the world's foremost primary producers.
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Affiliation(s)
- Elizabeth C Ruck
- Department of Biological Sciences, University of Arkansas, Fayetteville, AR, USA
| | - Samantha R Linard
- Department of Biological Sciences, University of Arkansas, Fayetteville, AR, USA
| | - Teofil Nakov
- Department of Biological Sciences, University of Arkansas, Fayetteville, AR, USA
| | - Edward C Theriot
- Section of Integrative Biology, University of Texas at Austin, Austin, TX, 78712, USA
| | - Andrew J Alverson
- Department of Biological Sciences, University of Arkansas, Fayetteville, AR, USA.
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Roy AC, Wilson GG, Edgell DR. Perpetuating the homing endonuclease life cycle: identification of mutations that modulate and change I-TevI cleavage preference. Nucleic Acids Res 2016; 44:7350-9. [PMID: 27387281 PMCID: PMC5009752 DOI: 10.1093/nar/gkw614] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Accepted: 06/27/2016] [Indexed: 11/14/2022] Open
Abstract
Homing endonucleases are sequence-tolerant DNA endonucleases that act as mobile genetic elements. The ability of homing endonucleases to cleave substrates with multiple nucleotide substitutions suggests a high degree of adaptability in that changing or modulating cleavage preference would require relatively few amino acid substitutions. Here, using directed evolution experiments with the GIY-YIG homing endonuclease I-TevI that targets the thymidylate synthase gene of phage T4, we readily isolated variants that dramatically broadened I-TevI cleavage preference, as well as variants that fine-tuned cleavage preference. By combining substitutions, we observed an ∼10 000-fold improvement in cleavage on some substrates not cleaved by the wild-type enzyme, correlating with a decrease in readout of information content at the cleavage site. Strikingly, we were able to change the cleavage preference of I-TevI to that of the isoschizomer I-BmoI which targets a different cleavage site in the thymidylate synthase gene, recapitulating the evolution of cleavage preference in this family of homing endonucleases. Our results define a strategy to isolate GIY-YIG nuclease domains with distinct cleavage preferences, and provide insight into how homing endonucleases may escape a dead-end life cycle in a population of saturated target sites by promoting transposition to different target sites.
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Affiliation(s)
- Alexander C Roy
- Department of Biochemistry, Schulich School of Medicine and Dentistry, Western University, London, ON, N6A 5C1, Canada
| | | | - David R Edgell
- Department of Biochemistry, Schulich School of Medicine and Dentistry, Western University, London, ON, N6A 5C1, Canada
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15
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Guha TK, Hausner G. Using Group II Introns for Attenuating the In Vitro and In Vivo Expression of a Homing Endonuclease. PLoS One 2016; 11:e0150097. [PMID: 26909494 PMCID: PMC4801052 DOI: 10.1371/journal.pone.0150097] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Accepted: 02/09/2016] [Indexed: 01/09/2023] Open
Abstract
In Chaetomium thermophilum (DSM 1495) within the mitochondrial DNA (mtDNA) small ribosomal subunit (rns) gene a group IIA1 intron interrupts an open reading frame (ORF) encoded within a group I intron (mS1247). This arrangement offers the opportunity to examine if the nested group II intron could be utilized as a regulatory element for the expression of the homing endonuclease (HEase). Constructs were generated where the codon-optimized ORF was interrupted with either the native group IIA1 intron or a group IIB type intron. This study showed that the expression of the HEase (in vivo) in Escherichia coli can be regulated by manipulating the splicing efficiency of the HEase ORF-embedded group II introns. Exogenous magnesium chloride (MgCl2) stimulated the expression of a functional HEase but the addition of cobalt chloride (CoCl2) to growth media antagonized the expression of HEase activity. Ultimately the ability to attenuate HEase activity might be useful in precision genome engineering, minimizing off target activities, or where pathways have to be altered during a specific growth phase.
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Affiliation(s)
- Tuhin Kumar Guha
- Department of Microbiology, University of Manitoba, Winnipeg, Canada
| | - Georg Hausner
- Department of Microbiology, University of Manitoba, Winnipeg, Canada
- * E-mail:
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16
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Kolondra A, Labedzka-Dmoch K, Wenda JM, Drzewicka K, Golik P. The transcriptome of Candida albicans mitochondria and the evolution of organellar transcription units in yeasts. BMC Genomics 2015; 16:827. [PMID: 26487099 PMCID: PMC4618339 DOI: 10.1186/s12864-015-2078-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 10/13/2015] [Indexed: 02/06/2023] Open
Abstract
Background Yeasts show remarkable variation in the organization of their mitochondrial genomes, yet there is little experimental data on organellar gene expression outside few model species. Candida albicans is interesting as a human pathogen, and as a representative of a clade that is distant from the model yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe. Unlike them, it encodes seven Complex I subunits in its mtDNA. No experimental data regarding organellar expression were available prior to this study. Methods We used high-throughput RNA sequencing and traditional RNA biology techniques to study the mitochondrial transcriptome of C. albicans strains BWP17 and SN148. Results The 14 protein-coding genes, two ribosomal RNA genes, and 24 tRNA genes are expressed as eight primary polycistronic transcription units. We also found transcriptional activity in the noncoding regions, and antisense transcripts that could be a part of a regulatory mechanism. The promoter sequence is a variant of the nonanucleotide identified in other yeast mtDNAs, but some of the active promoters show significant departures from the consensus. The primary transcripts are processed by a tRNA punctuation mechanism into the monocistronic and bicistronic mature RNAs. The steady state levels of various mature transcripts exhibit large differences that are a result of posttranscriptional regulation. Transcriptome analysis allowed to precisely annotate the positions of introns in the RNL (2), COB (2) and COX1 (4) genes, as well as to refine the annotation of tRNAs and rRNAs. Comparative study of the mitochondrial genome organization in various Candida species indicates that they undergo shuffling in blocks usually containing 2–3 genes, and that their arrangement in primary transcripts is not conserved. tRNA genes with their associated promoters, as well as GC-rich sequence elements play an important role in these evolutionary events. Conclusions The main evolutionary force shaping the mitochondrial genomes of yeasts is the frequent recombination, constantly breaking apart and joining genes into novel primary transcription units. The mitochondrial transcription units are constantly rearranged in evolution shaping the features of gene expression, such as the presence of secondary promoter sites that are inactive, or act as “booster” promoters, simplified transcriptional regulation and reliance on posttranscriptional mechanisms. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-2078-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Adam Kolondra
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106, Warsaw, Poland.
| | - Karolina Labedzka-Dmoch
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106, Warsaw, Poland.
| | - Joanna M Wenda
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106, Warsaw, Poland.
| | - Katarzyna Drzewicka
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106, Warsaw, Poland.
| | - Pawel Golik
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106, Warsaw, Poland. .,Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106, Warsaw, Poland.
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17
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Park S, Grewe F, Zhu A, Ruhlman TA, Sabir J, Mower JP, Jansen RK. Dynamic evolution of Geranium mitochondrial genomes through multiple horizontal and intracellular gene transfers. THE NEW PHYTOLOGIST 2015; 208:570-83. [PMID: 25989702 DOI: 10.1111/nph.13467] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Accepted: 04/15/2015] [Indexed: 05/20/2023]
Abstract
The exchange of genetic material between cellular organelles through intracellular gene transfer (IGT) or between species by horizontal gene transfer (HGT) has played an important role in plant mitochondrial genome evolution. The mitochondrial genomes of Geraniaceae display a number of unusual phenomena including highly accelerated rates of synonymous substitutions, extensive gene loss and reduction in RNA editing. Mitochondrial DNA sequences assembled for 17 species of Geranium revealed substantial reduction in gene and intron content relative to the ancestor of the Geranium lineage. Comparative analyses of nuclear transcriptome data suggest that a number of these sequences have been functionally relocated to the nucleus via IGT. Evidence for rampant HGT was detected in several Geranium species containing foreign organellar DNA from diverse eudicots, including many transfers from parasitic plants. One lineage has experienced multiple, independent HGT episodes, many of which occurred within the past 5.5 Myr. Both duplicative and recapture HGT were documented in Geranium lineages. The mitochondrial genome of Geranium brycei contains at least four independent HGT tracts that are absent in its nearest relative. Furthermore, G. brycei mitochondria carry two copies of the cox1 gene that differ in intron content, providing insight into contrasting hypotheses on cox1 intron evolution.
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Affiliation(s)
- Seongjun Park
- Department of Integrative Biology, University of Texas, Austin, TX, 78712, USA
| | - Felix Grewe
- Department of Agronomy and Horticulture, University of Nebraska, Lincoln, NE, 68588, USA
| | - Andan Zhu
- Department of Agronomy and Horticulture, University of Nebraska, Lincoln, NE, 68588, USA
| | - Tracey A Ruhlman
- Department of Integrative Biology, University of Texas, Austin, TX, 78712, USA
| | - Jamal Sabir
- Department of Biological Science, Biotechnology Research Group, King Abdulaziz University, Jeddah, 21589, Saudi Arabia
| | - Jeffrey P Mower
- Department of Agronomy and Horticulture, University of Nebraska, Lincoln, NE, 68588, USA
| | - Robert K Jansen
- Department of Integrative Biology, University of Texas, Austin, TX, 78712, USA
- Department of Biological Science, Biotechnology Research Group, King Abdulaziz University, Jeddah, 21589, Saudi Arabia
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18
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Comparison of mitochondrial genomes provides insights into intron dynamics and evolution in the caterpillar fungus Cordyceps militaris. Fungal Genet Biol 2015; 77:95-107. [PMID: 25896956 DOI: 10.1016/j.fgb.2015.04.009] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Revised: 04/09/2015] [Accepted: 04/11/2015] [Indexed: 12/16/2022]
Abstract
Intra-specific comparison of mitochondrial genomes can help elucidate the evolution of a species, however it has not been performed for hypocrealean fungi that form diverse symbiotic associations with other organisms. In this study, comparative analyses of three completely sequenced mitochondrial genomes of a hypocrealean fungus, Cordyceps militaris, the type species of Cordyceps genus, revealed that the introns were the main contributors to mitochondrial genome size variations among strains. Mitochondrial genes in C. militaris have been invaded by group I introns in at least eight positions. PCR assays of various C. militaris isolates showed abundant variations of intron presence/absence among strains at seven of the eight intronic loci. Although the ancestral intron pattern was inferred to contain all eight introns, loss and/or gain events occurred for seven of the eight introns. These introns invaded the C. militaris mitochondrial genome probably by horizontal transfer from other fungi, and intron insertions into intronless genes in C. militaris were accompanied by co-conversions of upstream exon sequences especially for those introns targeting protein-coding genes. We also detected phylogenetic congruence between the intron and exon trees at each individual locus, consistent with the ancestral mitochondria of C. militaris as having all eight introns. This study helps to explain the evolution of C. militaris mitochondrial genomes and will facilitate population genetic studies of this medicinally important fungus.
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19
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Mullany P, Allan E, Roberts AP. Mobile genetic elements in Clostridium difficile and their role in genome function. Res Microbiol 2015; 166:361-7. [PMID: 25576774 PMCID: PMC4430133 DOI: 10.1016/j.resmic.2014.12.005] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Revised: 12/10/2014] [Accepted: 12/13/2014] [Indexed: 11/25/2022]
Abstract
Approximately 11% the Clostridium difficile genome is made up of mobile genetic elements which have a profound effect on the biology of the organism. This includes transfer of antibiotic resistance and other factors that allow the organism to survive challenging environments, modulation of toxin gene expression, transfer of the toxin genes themselves and the conversion of non-toxigenic strains to toxin producers. Mobile genetic elements have also been adapted by investigators to probe the biology of the organism and the various ways in which these have been used are reviewed.
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Affiliation(s)
- Peter Mullany
- Department of Microbial Diseases, UCL Eastman Dental Institute, University College London, 256 Gray's Inn Road, London WC1X 8LD, UK.
| | - Elaine Allan
- Department of Microbial Diseases, UCL Eastman Dental Institute, University College London, 256 Gray's Inn Road, London WC1X 8LD, UK.
| | - Adam P Roberts
- Department of Microbial Diseases, UCL Eastman Dental Institute, University College London, 256 Gray's Inn Road, London WC1X 8LD, UK.
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20
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Moran JV. 2013 Curt Stern Award Address. Am J Hum Genet 2014; 94:340-8. [PMID: 24607386 DOI: 10.1016/j.ajhg.2014.01.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Accepted: 01/28/2014] [Indexed: 11/29/2022] Open
Affiliation(s)
- John V Moran
- Departments of Human Genetics and Internal Medicine, 1241 East Catherine Street, University of Michigan Medical School, Ann Arbor, MI 48109-5618, USA; Howard Hughes Medical Institute.
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21
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Epinat JC. A yeast-based recombination assay for homing endonuclease activity. Methods Mol Biol 2014; 1123:105-26. [PMID: 24510264 DOI: 10.1007/978-1-62703-968-0_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Homing endonucleases (HEs) are natural enzymes that cleave long DNA target with a high specificity and trigger homologous recombination at the exact site of the break. Such mechanisms can thus be used for all the applications covered today by the generic name of "genome engineering": targeted sequence insertion, removal, or editing. However, before being able to address those applications, the engineering of HEs must be mastered so that any potential target would be efficiently and specifically recognized and cleaved. Working on the I-CreI model, we have developed a very powerful platform to generate HEs with new tailored specificity. We have put in place the first in vivo, functional, high throughput assay to generate I-CreI variants and measure their activity. We use semi-rational design combined with proprietary in silico predictions to design and synthesize I-CreI mutants that are tested for their capacity to induce homologous recombination in a yeast cell. The process has been standardized and robotized so that we can generate thousands of I-CreI derivatives, characterize their cleavage profile, and deliver them for further applications in the research, therapeutic, or agrobusiness fields.
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22
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Roberts AP, Allan E, Mullany P. The impact of horizontal gene transfer on the biology of Clostridium difficile. Adv Microb Physiol 2014; 65:63-82. [PMID: 25476764 DOI: 10.1016/bs.ampbs.2014.08.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Clostridium difficile infection (CDI) is now recognised as the main cause of healthcare associated diarrhoea. Over the recent years there has been a change in the epidemiology of CDI with certain related strains dominating infection. These strains have been termed hyper-virulent and have successfully spread across the globe. Many C. difficile strains have had their genomes completely sequenced allowing researchers to build up a very detailed picture of the contribution of horizontal gene transfer to the adaptive potential, through the acquisition of mobile DNA, of this organism. Here, we review and discuss the contribution of mobile genetic elements to the biology of this clinically important pathogen.
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Abstract
The abundance of group I introns, intragenic RNA sequences capable of self-splicing, in Gram-positive bacteriophage genomes, is illustrated by various new group I introns recently described in Staphylococcus phage genomes. These introns were found to interrupt DNA metabolism genes as well as late genes. These group I introns often code for homing endonucleases, which promote lateral transfer of group I introns, thereby enabling spread through a population. Homing endonucleases encoded by group I introns in Staphylococcus phage genomes were predicted to belong to the GIY-YIG, LAGLIDADG, HNH or EDxHD family of endonucleases. The group I intron distribution in Staphylococcus phage genomes exemplifies the homology between these introns as well as the encoded endonucleases. Despite several suggested functions, the role of group I introns in bacteriophages remains unclear or might be nonexistent. However, transcriptome analysis might provide additional information to elucidate the possible purpose of group I introns in phage genomes.
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Affiliation(s)
- Rob Lavigne
- Katholieke Universiteit Leuven, Department of Biosystems, Kasteelpark Arenberg 21, Bus 2462, Leuven, Belgium
| | - Katrien Vandersteegen
- Katholieke Universiteit Leuven, Department of Biosystems, Kasteelpark Arenberg 21, Bus 2462, Leuven, Belgium
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24
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Xu C, Wang C, Sun X, Zhang R, Gleason ML, Eiji T, Sun G. Multiple group I introns in the small-subunit rDNA of Botryosphaeria dothidea: implication for intraspecific genetic diversity. PLoS One 2013; 8:e67808. [PMID: 23844098 PMCID: PMC3699495 DOI: 10.1371/journal.pone.0067808] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Accepted: 05/22/2013] [Indexed: 11/18/2022] Open
Abstract
Botryosphaeria dothidea is a widespread and economically important pathogen on various fruit trees, and it often causes die-back and canker on limbs and fruit rot. In characterizing intraspecies genetic variation within this fungus, group I introns, rich in rDNA of fungi, may provide a productive region for exploration. In this research, we analysed complete small subunit (SSU) ribosomal DNA (rDNA) sequences of 37 B. dothidea strains, and found four insertions, designated Bdo.S943, Bdo.S1199-A, Bdo.S1199-B and Bdo.S1506, at three positions. Sequence analysis and structure prediction revealed that both Bdo.S943 and Bdo.S1506 belonged to subgroup IC1 of group I introns, whereas Bdo.S1199-A and Bdo.S1199-B corresponded to group IE introns. Moreover, Bdo.S1199-A was found to host an open reading frame (ORF) for encoding the homing endonuclease (HE), whereas Bdo.S1199-B, an evolutionary descendant of Bdo.S1199-A, included a degenerate HE. The above four introns were novel, and were the first group I introns observed and characterized in this species. Differential distribution of these introns revealed that all strains could be separated into four genotypes. Genotype III (no intron) and genotype IV (Bdo.S1199-B) were each found in only one strain, whereas genotype I (Bdo.S1199-A) and genotype II (Bdo.S943 and Bdo.S1506) occurred in 95% of the strains. There is a correlation between B. dothidea genotypes and hosts or geographic locations. Thus, these newly discovered group I introns can help to advance understanding of genetic differentiation within B. dothidea.
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Affiliation(s)
- Chao Xu
- Key Laboratory of Crop Stress Biology in Arid Areas, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi, China
| | - Chunsheng Wang
- Key Laboratory of Crop Stress Biology in Arid Areas, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi, China
| | - Xinyao Sun
- Key Laboratory of Crop Stress Biology in Arid Areas, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi, China
| | - Rong Zhang
- Key Laboratory of Crop Stress Biology in Arid Areas, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi, China
| | - Mark L. Gleason
- Department of Plant Pathology and Microbiology, Iowa State University, Ames, Iowa, United States of America
| | - Tanaka Eiji
- Ishikawa Prefectural University, Ishikawa, Japan
| | - Guangyu Sun
- Key Laboratory of Crop Stress Biology in Arid Areas, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi, China
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Chakraborty C, George Priya Doss C, Bandyopadhyay S, Sarkar BK, Syed Haneef SA. Mapping the Structural Topology of IRS Family Cascades Through Computational Biology. Cell Biochem Biophys 2013; 67:1319-31. [DOI: 10.1007/s12013-013-9664-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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26
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Gaillardin C, Neuvéglise C, Kerscher S, Nicaud JM. Mitochondrial genomes of yeasts of the Yarrowia clade. FEMS Yeast Res 2012; 12:317-31. [PMID: 22188421 DOI: 10.1111/j.1567-1364.2011.00782.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2011] [Revised: 11/25/2011] [Accepted: 12/07/2011] [Indexed: 12/13/2022] Open
Abstract
Candida alimentaria, Candida deformans, Candida galli, and Candida phangngensis have been recently reported to be the close relatives of Yarrowia lipolytica. To explore this clade of yeasts, we sequenced the mitochondrial genome (mtDNA) of these four species and compared it with the mtDNA of Y. lipolytica. The five mtDNAs exhibit a similar architecture and a high level of similarity of protein coding sequences. Genome sizes are variable, ranging from 28 017 bp in C. phangngensis to 48 508 bp in C. galli, mainly because of the variations in intron size and number. All introns are of group I, except for a group II intron inserted in the cob gene of a single species, C. galli. Putative endonuclease coding sequences were present in most group I introns, but also twice as free-standing ORFs in C. galli. Phylogenetic relationships of the five species were explored using protein alignments. No close relative of the Yarrowia clade could be identified, but protein and rRNA gene orders were partially conserved in the mtDNA of Candida salmanticensis.
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27
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Li H, Ulge UY, Hovde BT, Doyle LA, Monnat RJ. Comprehensive homing endonuclease target site specificity profiling reveals evolutionary constraints and enables genome engineering applications. Nucleic Acids Res 2011; 40:2587-98. [PMID: 22121229 PMCID: PMC3315327 DOI: 10.1093/nar/gkr1072] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Homing endonucleases (HEs) promote the evolutionary persistence of selfish DNA elements by catalyzing element lateral transfer into new host organisms. The high site specificity of this lateral transfer reaction, termed homing, reflects both the length (14-40 bp) and the limited tolerance of target or homing sites for base pair changes. In order to better understand molecular determinants of homing, we systematically determined the binding and cleavage properties of all single base pair variant target sites of the canonical LAGLIDADG homing endonucleases I-CreI and I-MsoI. These Chlorophyta algal HEs have very similar three-dimensional folds and recognize nearly identical 22 bp target sites, but use substantially different sets of DNA-protein contacts to mediate site-specific recognition and cleavage. The site specificity differences between I-CreI and I-MsoI suggest different evolutionary strategies for HE persistence. These differences also provide practical guidance in target site finding, and in the generation of HE variants with high site specificity and cleavage activity, to enable genome engineering applications.
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Affiliation(s)
- Hui Li
- Department of Pathology, University of Washington, Box 357705, Seattle, WA 98195, USA
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28
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Taylor GK, Heiter DF, Pietrokovski S, Stoddard BL. Activity, specificity and structure of I-Bth0305I: a representative of a new homing endonuclease family. Nucleic Acids Res 2011; 39:9705-19. [PMID: 21890897 PMCID: PMC3239194 DOI: 10.1093/nar/gkr669] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Novel family of putative homing endonuclease genes was recently discovered during analyses of metagenomic and genomic sequence data. One such protein is encoded within a group I intron that resides in the recA gene of the Bacillus thuringiensis 0305ϕ8–36 bacteriophage. Named I-Bth0305I, the endonuclease cleaves a DNA target in the uninterrupted recA gene at a position immediately adjacent to the intron insertion site. The enzyme displays a multidomain, homodimeric architecture and footprints a DNA region of ∼60 bp. Its highest specificity corresponds to a 14-bp pseudopalindromic sequence that is directly centered across the DNA cleavage site. Unlike many homing endonucleases, the specificity profile of the enzyme is evenly distributed across much of its target site, such that few single base pair substitutions cause a significant decrease in cleavage activity. A crystal structure of its C-terminal domain confirms a nuclease fold that is homologous to very short patch repair (Vsr) endonucleases. The domain architecture and DNA recognition profile displayed by I-Bth0305I, which is the prototype of a homing lineage that we term the ‘EDxHD’ family, are distinct from previously characterized homing endonucleases.
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Affiliation(s)
- Gregory K Taylor
- Graduate Program in Molecular and Cellular Biology and the Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98019, USA
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29
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Harris LB, Rogers SO. Evolution of small putative group I introns in the SSU rRNA gene locus of Phialophora species. BMC Res Notes 2011; 4:258. [PMID: 21781325 PMCID: PMC3160393 DOI: 10.1186/1756-0500-4-258] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2011] [Accepted: 07/22/2011] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Group I introns (specifically subgroup IC1) are common in the nuclear ribosomal RNA genes of fungi. While most range in length from more than 200 to nearly 1800 nucleotides (nt) in length, several small putative (or degenerate) group I introns have been described that are between 56 and 81 nt. Although small, previously we demonstrated that the PaSSU intron in the rRNA small subunit gene of Phialophora americana isolate Wang 1046 is capable of in vitro splicing using a standard group I intron pathway, thus qualifying it as a functional ribozyme. FINDINGS Here, we describe eight short putative group I introns, ranging in length from 63 to 75 nt, in the rRNA small subunit genes of Phialophora isolates, a fungal genus that ranges from saprobic to pathogenic on plants and animals. All contain putative pairing regions P1, P7, and P10, as well as a pairing region formed between the middle of the intron and part of the 3' exon. The other pairing regions common in the core of standard group I introns are absent. However, parts of the 3' exon may aid in the stabilization of these small introns. Although the eight putative group I introns were from at least three species of Phialophora, phylogenetic analysis indicated that the eight are monophyletic. They are also monophyletic with the small introns of two lichen-forming fungi, Porpidia crustulata and Arthonia lapidicola. CONCLUSIONS The small putative group I introns in Phialophora have common features that may represent group I introns at their minima. They appear to have a single origin as indicated by their monophyly in phylogenetic analyses.
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Affiliation(s)
- Lorena B Harris
- Department of Biological Sciences, Bowling Green State University, Bowling Green, OH 43403, USA.
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30
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Petersen K, Schöttler MA, Karcher D, Thiele W, Bock R. Elimination of a group II intron from a plastid gene causes a mutant phenotype. Nucleic Acids Res 2011; 39:5181-92. [PMID: 21357608 PMCID: PMC3130276 DOI: 10.1093/nar/gkr105] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2010] [Revised: 01/24/2011] [Accepted: 02/08/2011] [Indexed: 12/21/2022] Open
Abstract
Group II introns are found in bacteria and cell organelles (plastids, mitochondria) and are thought to represent the evolutionary ancestors of spliceosomal introns. It is generally believed that group II introns are selfish genetic elements that do not have any function. Here, we have scrutinized this assumption by analyzing two group II introns that interrupt a plastid gene (ycf3) involved in photosystem assembly. Using stable transformation of the plastid genome, we have generated mutant plants that lack either intron 1 or intron 2 or both. Interestingly, the deletion of intron 1 caused a strong mutant phenotype. We show that the mutants are deficient in photosystem I and that this deficiency is directly related to impaired ycf3 function. We further show that, upon deletion of intron 1, the splicing of intron 2 is strongly inhibited. Our data demonstrate that (i) the loss of a group II intron is not necessarily phenotypically neutral and (ii) the splicing of one intron can depend on the presence of another.
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Affiliation(s)
| | | | | | | | - Ralph Bock
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, D-14476 Potsdam-Golm, Germany
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Stoddard BL. Homing endonucleases: from microbial genetic invaders to reagents for targeted DNA modification. Structure 2011; 19:7-15. [PMID: 21220111 DOI: 10.1016/j.str.2010.12.003] [Citation(s) in RCA: 214] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2010] [Revised: 12/14/2010] [Accepted: 12/15/2010] [Indexed: 12/23/2022]
Abstract
Homing endonucleases are microbial DNA-cleaving enzymes that mobilize their own reading frames by generating double strand breaks at specific genomic invasion sites. These proteins display an economy of size, and yet recognize long DNA sequences (typically 20 to 30 base pairs). They exhibit a wide range of fidelity at individual nucleotide positions in a manner that is strongly influenced by host constraints on the coding sequence of the targeted gene. The activity of these proteins leads to site-specific recombination events that can result in the insertion, deletion, mutation, or correction of DNA sequences. Over the past fifteen years, the crystal structures of representatives from several homing endonuclease families have been solved, and methods have been described to create variants of these enzymes that cleave novel DNA targets. Engineered homing endonucleases proteins are now being used to generate targeted genomic modifications for a variety of biotech and medical applications.
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Affiliation(s)
- Barry L Stoddard
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue N., A3-025, Seattle, WA 98109, USA.
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Jacobs J, Kück U. Function of chloroplast RNA-binding proteins. Cell Mol Life Sci 2011; 68:735-48. [PMID: 20848156 PMCID: PMC11115000 DOI: 10.1007/s00018-010-0523-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Revised: 08/25/2010] [Accepted: 08/30/2010] [Indexed: 12/18/2022]
Abstract
Chloroplasts are eukaryotic organelles which represent evolutionary chimera with proteins that have been derived from either a prokaryotic endosymbiont or a eukaryotic host. Chloroplast gene expression starts with transcription of RNA and is followed by multiple post-transcriptional processes which are mediated mainly by an as yet unknown number of RNA-binding proteins. Here, we review the literature to date on the structure and function of these chloroplast RNA-binding proteins. For example, the functional protein domains involved in RNA binding, such as the RNA-recognition motifs, the chloroplast RNA-splicing and ribosome maturation domains, and the pentatricopeptide-repeat motifs, are summarized. We also describe biochemical and forward genetic approaches that led to the identification of proteins modifying RNA stability or carrying out RNA splicing or editing. Such data will greatly contribute to a better understanding of the biogenesis of a unique organelle found in all photosynthetic organisms.
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Affiliation(s)
- Jessica Jacobs
- Department for General and Molecular Biology, Ruhr-University Bochum, Universitätsstraße 150, Bochum, Germany.
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33
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Expanding the definition of class 3 inteins and their proposed phage origin. J Bacteriol 2011; 193:2035-41. [PMID: 21317331 DOI: 10.1128/jb.01407-10] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Inteins are the protein equivalent of introns. Their protein splicing activity is essential for the host protein's maturation and function. Inteins are grouped into three classes based on sequence signature and splicing mechanism. The sequence signature of the recently characterized class 3 inteins is a noncontiguous Trp-Cys-Thr (WCT) motif and the absence of the standard class 1 Cys¹ or Ser¹ N-terminal nucleophile. The intein N-terminal Cys¹ or Ser¹ residue is essential for splicing in class 1 inteins. The mycobacteriophage Catera Gp206, Nocardioides sp. strain JS614 TOPRIM, and Thermobifida fusca YX Tfu2914 inteins have a mixture of class 1 and class 3 motifs. They carry the class 3 Trp-Cys-Thr motif and have the standard class 1 N-terminal Ser¹ or Cys¹. This study determined which class the mycobacteriophage Catera Gp206 and Nocardioides sp. JS614 TOPRIM inteins belong to based on catalytic mechanism. The mycobacteriophage Catera Gp206 intein (starting with Ser¹) is a class 3 intein, and its Ser¹ residue is not required for splicing. Based on phylogenetic analysis, we propose that class 3 inteins arose from a single mutated intein that was spread by phage into predominantly helicase genes in various phages and their hosts.
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Kreuzer KN, Brister JR. Initiation of bacteriophage T4 DNA replication and replication fork dynamics: a review in the Virology Journal series on bacteriophage T4 and its relatives. Virol J 2010; 7:358. [PMID: 21129203 PMCID: PMC3016281 DOI: 10.1186/1743-422x-7-358] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2010] [Accepted: 12/03/2010] [Indexed: 11/10/2022] Open
Abstract
Bacteriophage T4 initiates DNA replication from specialized structures that form in its genome. Immediately after infection, RNA-DNA hybrids (R-loops) occur on (at least some) replication origins, with the annealed RNA serving as a primer for leading-strand synthesis in one direction. As the infection progresses, replication initiation becomes dependent on recombination proteins in a process called recombination-dependent replication (RDR). RDR occurs when the replication machinery is assembled onto D-loop recombination intermediates, and in this case, the invading 3' DNA end is used as a primer for leading strand synthesis. Over the last 15 years, these two modes of T4 DNA replication initiation have been studied in vivo using a variety of approaches, including replication of plasmids with segments of the T4 genome, analysis of replication intermediates by two-dimensional gel electrophoresis, and genomic approaches that measure DNA copy number as the infection progresses. In addition, biochemical approaches have reconstituted replication from origin R-loop structures and have clarified some detailed roles of both replication and recombination proteins in the process of RDR and related pathways. We will also discuss the parallels between T4 DNA replication modes and similar events in cellular and eukaryotic organelle DNA replication, and close with some current questions of interest concerning the mechanisms of replication, recombination and repair in phage T4.
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Affiliation(s)
- Kenneth N Kreuzer
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710 USA
| | - J Rodney Brister
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894 USA
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A maturase that specifically stabilizes and activates its cognate group I intron at high temperatures. Biochimie 2010; 93:533-41. [PMID: 21129434 DOI: 10.1016/j.biochi.2010.11.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2010] [Accepted: 11/22/2010] [Indexed: 11/23/2022]
Abstract
Folding of large structured RNAs into their functional tertiary structures at high temperatures is challenging. Here we show that I-TnaI protein, a small LAGLIDADG homing endonuclease encoded by a group I intron from a hyperthermophilic bacterium, acts as a maturase that is essential for the catalytic activity of this intron at high temperatures and physiological cationic conditions. I-TnaI specifically binds to and induces tertiary packing of the P4-P6 domain of the intron; this RNA-protein complex might serve as a thermostable platform for active folding of the entire intron. Interestingly, the binding affinity of I-TnaI to its cognate intron RNA largely increases with temperature; over 30-fold stronger binding at higher temperatures relative to 37 °C correlates with a switch from an entropy-driven (37 °C) to an enthalpy-driven (55-60 °C) interaction mode. This binding mode may represent a novel strategy how an RNA binding protein can promote the function of its target RNA specifically at high temperatures.
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36
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Chan SH, Stoddard BL, Xu SY. Natural and engineered nicking endonucleases--from cleavage mechanism to engineering of strand-specificity. Nucleic Acids Res 2010; 39:1-18. [PMID: 20805246 PMCID: PMC3017599 DOI: 10.1093/nar/gkq742] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Restriction endonucleases (REases) are highly specific DNA scissors that have facilitated the development of modern molecular biology. Intensive studies of double strand (ds) cleavage activity of Type IIP REases, which recognize 4–8 bp palindromic sequences, have revealed a variety of mechanisms of molecular recognition and catalysis. Less well-studied are REases which cleave only one of the strands of dsDNA, creating a nick instead of a ds break. Naturally occurring nicking endonucleases (NEases) range from frequent cutters such as Nt.CviPII (^CCD; ^ denotes the cleavage site) to rare-cutting homing endonucleases (HEases) such as I-HmuI. In addition to these bona fida NEases, individual subunits of some heterodimeric Type IIS REases have recently been shown to be natural NEases. The discovery and characterization of more REases that recognize asymmetric sequences, particularly Types IIS and IIA REases, has revealed recognition and cleavage mechanisms drastically different from the canonical Type IIP mechanisms, and has allowed researchers to engineer highly strand-specific NEases. Monomeric LAGLIDADG HEases use two separate catalytic sites for cleavage. Exploitation of this characteristic has also resulted in useful nicking HEases. This review aims at providing an overview of the cleavage mechanisms of Types IIS and IIA REases and LAGLIDADG HEases, the engineering of their nicking variants, and the applications of NEases and nicking HEases.
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37
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Kerscher S, Durstewitz G, Casaregola S, Gaillardin C, Brandt U. The complete mitochondrial genome of yarrowia lipolytica. Comp Funct Genomics 2010; 2:80-90. [PMID: 18628906 PMCID: PMC2447202 DOI: 10.1002/cfg.72] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2001] [Accepted: 02/10/2001] [Indexed: 11/16/2022] Open
Abstract
We here report the complete nucleotide sequence of the 47.9 kb mitochondrial (mt) genome
from the obligate aerobic yeast Yarrowia lipolytica. It encodes, all on the same strand,
seven subunits of NADH: ubiquinone oxidoreductase (ND1-6, ND4L), apocytochrome
b (COB), three subunits of cytochrome oxidase (COX1, 2, 3), three subunits of ATP
synthetase (ATP6, 8 and 9), small and large ribosomal RNAs and an incomplete set of
tRNAs. The Y. lipolytica mt genome is very similar to the Hansenula wingei mt genome,
as judged from blocks of conserved gene order and from sequence homology. The extra
DNA in the Y. lipolytica mt genome consists of 17 group 1 introns and stretches of A+Trich
sequence, interspersed with potentially transposable GC clusters. The usual mould mt
genetic code is used. Interestingly, there is no tRNA able to read CGN (arginine) codons.
CGN codons could not be found in exonic open reading frames, whereas they do occur in
intronic open reading frames. However, several of the intronic open reading frames have
accumulated mutations and must be regarded as pseudogenes. We propose that this may
have been triggered by the presence of untranslatable CGN codons. This sequence is
available under EMBL Accession No. AJ307410.
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Affiliation(s)
- S Kerscher
- Universitätsklinikum Frankfurt, Institut für Biochemie I, Zentrum der Biologischen Chemie, Frankfurt am Main D-60590, Germany.
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38
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Ashworth J, Taylor GK, Havranek JJ, Quadri SA, Stoddard BL, Baker D. Computational reprogramming of homing endonuclease specificity at multiple adjacent base pairs. Nucleic Acids Res 2010; 38:5601-8. [PMID: 20435674 PMCID: PMC2938204 DOI: 10.1093/nar/gkq283] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Site-specific homing endonucleases are capable of inducing gene conversion via homologous recombination. Reprogramming their cleavage specificities allows the targeting of specific biological sites for gene correction or conversion. We used computational protein design to alter the cleavage specificity of I-MsoI for three contiguous base pair substitutions, resulting in an endonuclease whose activity and specificity for its new site rival that of wild-type I-MsoI for the original site. Concerted design for all simultaneous substitutions was more successful than a modular approach against individual substitutions, highlighting the importance of context-dependent redesign and optimization of protein–DNA interactions. We then used computational design based on the crystal structure of the designed complex, which revealed significant unanticipated shifts in DNA conformation, to create an endonuclease that specifically cleaves a site with four contiguous base pair substitutions. Our results demonstrate that specificity switches for multiple concerted base pair substitutions can be computationally designed, and that iteration between design and structure determination provides a route to large scale reprogramming of specificity.
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Affiliation(s)
- Justin Ashworth
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA.
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39
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Sethuraman J, Majer A, Friedrich NC, Edgell DR, Hausner G. Genes within Genes: Multiple LAGLIDADG Homing Endonucleases Target the Ribosomal Protein S3 Gene Encoded within an rnl Group I Intron of Ophiostoma and Related Taxa. Mol Biol Evol 2009; 26:2299-315. [DOI: 10.1093/molbev/msp145] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Hoshina R, Imamura N. Phylogenetically Close Group I Introns with Different Positions among Paramecium bursaria Photobionts Imply a Primitive Stage of Intron Diversification. Mol Biol Evol 2009; 26:1309-19. [DOI: 10.1093/molbev/msp044] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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41
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Li H, Pellenz S, Ulge U, Stoddard BL, Monnat RJ. Generation of single-chain LAGLIDADG homing endonucleases from native homodimeric precursor proteins. Nucleic Acids Res 2009; 37:1650-62. [PMID: 19153140 PMCID: PMC2655683 DOI: 10.1093/nar/gkp004] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Homing endonucleases (HEs) cut long DNA target sites with high specificity to initiate and target the lateral transfer of mobile introns or inteins. This high site specificity of HEs makes them attractive reagents for gene targeting to promote DNA modification or repair. We have generated several hundred catalytically active, monomerized versions of the well-characterized homodimeric I-CreI and I-MsoI LAGLIDADG family homing endonuclease (LHE) proteins. Representative monomerized I-CreI and I-MsoI proteins (collectively termed mCreIs or mMsoIs) were characterized in detail by using a combination of biochemical, biophysical and structural approaches. We also demonstrated that both mCreI and mMsoI proteins can promote cleavage-dependent recombination in human cells. The use of single chain LHEs should simplify gene modification and targeting by requiring the expression of a single small protein in cells, rather than the coordinate expression of two separate protein coding genes as is required when using engineered heterodimeric zinc finger or homing endonuclease proteins.
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Affiliation(s)
- Hui Li
- Department of Pathology, University of Washington, Box 357705, Seattle, WA 98195, USA
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42
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Zhao L, Pellenz S, Stoddard BL. Activity and specificity of the bacterial PD-(D/E)XK homing endonuclease I-Ssp6803I. J Mol Biol 2008; 385:1498-510. [PMID: 19038269 DOI: 10.1016/j.jmb.2008.10.096] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2008] [Revised: 10/28/2008] [Accepted: 10/31/2008] [Indexed: 10/21/2022]
Abstract
The restriction endonuclease fold [a three-layer alpha-beta sandwich containing variations of the PD-(D/E)XK nuclease motif] has been greatly diversified during evolution, facilitating its use for many biological functions. Here we characterize DNA binding and cleavage by the PD-(D/E)XK homing endonuclease I-Ssp6803I. Unlike most restriction endonucleases harboring the same core fold, the specificity profile of this enzyme extends over a long (17 bp) target site. The DNA binding and cleavage specificity profiles of this enzyme were independently determined and found to be highly correlated. However, the DNA target sequence contains several positions where binding and cleavage activities are not tightly coupled: individual DNA base-pair substitutions at those positions that significantly decrease cleavage activity have minor effects on binding affinity. These changes in the DNA target sequence appear to correspond to substitutions that uniquely increase the free energy change between the ground state and the transition state, rather than simply decreasing the overall DNA binding affinity. The specificity of the enzyme reflects constraints on its host gene and limitations imposed by the enzyme's quaternary structure and illustrate the highly diverse repertoire of DNA recognition specificities that can be adopted by the related folds surrounding the PD-(D/E)XK nuclease motif.
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Affiliation(s)
- Lei Zhao
- Graduate Program in Molecular Biophysics, Structure and Design, University of Washington, Seattle, WA 98195, USA
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Milstein D, Oliveira MC, Martins FM, Matioli SR. Group I introns and associated homing endonuclease genes reveals a clinal structure for Porphyra spiralis var. amplifolia (Bangiales, Rhodophyta) along the Eastern coast of South America. BMC Evol Biol 2008; 8:308. [PMID: 18992156 PMCID: PMC2585584 DOI: 10.1186/1471-2148-8-308] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2008] [Accepted: 11/07/2008] [Indexed: 11/24/2022] Open
Abstract
Background Group I introns are found in the nuclear small subunit ribosomal RNA gene (SSU rDNA) of some species of the genus Porphyra (Bangiales, Rhodophyta). Size polymorphisms in group I introns has been interpreted as the result of the degeneration of homing endonuclease genes (HEG) inserted in peripheral loops of intron paired elements. In this study, intron size polymorphisms were characterized for different Porphyra spiralis var. amplifolia (PSA) populations on the Southern Brazilian coast, and were used to infer genetic relationships and genetic structure of these PSA populations, in addition to cox2-3 and rbcL-S regions. Introns of different sizes were tested qualitatively for in vitro self-splicing. Results Five intron size polymorphisms within 17 haplotypes were obtained from 80 individuals representing eight localities along the distribution of PSA in the Eastern coast of South America. In order to infer genetic structure and genetic relationships of PSA, these polymorphisms and haplotypes were used as markers for pairwise Fst analyses, Mantel's test and median joining network. The five cox2-3 haplotypes and the unique rbcL-S haplotype were used as markers for summary statistics, neutrality tests Tajima's D and Fu's Fs and for median joining network analyses. An event of demographic expansion from a population with low effective number, followed by a pattern of isolation by distance was obtained for PSA populations with the three analyses. In vitro experiments have shown that introns of different lengths were able to self-splice from pre-RNA transcripts. Conclusion The findings indicated that degenerated HEGs are reminiscent of the presence of a full-length and functional HEG, once fixed for PSA populations. The cline of HEG degeneration determined the pattern of isolation by distance. Analyses with the other markers indicated an event of demographic expansion from a population with low effective number. The different degrees of degeneration of the HEG do not refrain intron self-splicing. To our knowledge, this was the first study to address intraspecific evolutionary history of a nuclear group I intron; to use nuclear, mitochondrial and chloroplast DNA for population level analyses of Porphyra; and intron size polymorphism as a marker for population genetics.
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Affiliation(s)
- Daniela Milstein
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, Rua do Matão, 277, cep 05508-900, Brazil.
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Pantou MP, Kouvelis VN, Typas MA. The complete mitochondrial genome of Fusarium oxysporum: Insights into fungal mitochondrial evolution. Gene 2008; 419:7-15. [DOI: 10.1016/j.gene.2008.04.009] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2007] [Revised: 04/21/2008] [Accepted: 04/21/2008] [Indexed: 11/26/2022]
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45
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Juhász A, Pfeiffer I, Keszthelyi A, Kucsera J, Vágvölgyi C, Hamari Z. Comparative analysis of the complete mitochondrial genomes of Aspergillus niger mtDNA type 1a and Aspergillus tubingensis mtDNA type 2b. FEMS Microbiol Lett 2008; 281:51-7. [PMID: 18318841 DOI: 10.1111/j.1574-6968.2008.01077.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
To understand the differences in the organization of mitochondrial genomes of the very closely related Aspergillus niger and Aspergillus tubingensis species, we determined the complete genome sequence of the 1a mtDNA type of A. niger and 2b mtDNA type of A. tubingensis and now we provide a comparative analysis of the two mtDNAs. We found that (1) the organization (gene content and order) of the two genomes is almost identical and (2) the size difference between them is principally attributed to the different intron content of their cox1, atp9 and ndh4L genes.
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Affiliation(s)
- Akos Juhász
- Department of Microbiology, Faculty of Sciences, University of Szeged, Szeged, Hungary
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46
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Ikuta K, Kawai H, Müller DG, Ohama T. Recurrent invasion of mitochondrial group II introns in specimens of Pylaiella littoralis (brown alga), collected worldwide. Curr Genet 2008; 53:207-16. [PMID: 18224322 DOI: 10.1007/s00294-008-0178-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2007] [Revised: 01/12/2008] [Accepted: 01/14/2008] [Indexed: 10/22/2022]
Abstract
The mitochondrial genome of a filamentous brown alga Pylaiella littoralis (strain CCMP 1907) has been reported to contain four group IIB introns in the LSU rRNA gene and three group IIA introns in the cox1 gene. We found extreme variability in the number of group II introns for these two genes by analyzing eight P. littoralis specimens collected at worldwide habitats. The first intron of the LSU rRNA gene from a specimen collected in France and the fourth intron from a specimen harvested in Japan exhibited an exceptionally long evolutionary distance when compared with the cognate introns found in P. littoralis specimens. Moreover, these introns harbored an intact or nearly intact tripartite ORF, suggesting they are the result of a recent invasion of cognate introns. Based on the fact that many of the target sites were intronless, we propose that opportunity of intron infection is the bottleneck step of the group II intron cycle which consists of invasion, degeneration, and complete loss from the target site.
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Affiliation(s)
- Kyosuke Ikuta
- Department of Biology, Osaka Kyoiku University, Kashiwara, Osaka 582-8582, Japan.
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47
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Brok-Volchanskaya VS, Kadyrov FA, Sivogrivov DE, Kolosov PM, Sokolov AS, Shlyapnikov MG, Kryukov VM, Granovsky IE. Phage T4 SegB protein is a homing endonuclease required for the preferred inheritance of T4 tRNA gene region occurring in co-infection with a related phage. Nucleic Acids Res 2008; 36:2094-105. [PMID: 18281701 PMCID: PMC2330249 DOI: 10.1093/nar/gkn053] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Homing endonucleases initiate nonreciprocal transfer of DNA segments containing their own genes and the flanking sequences by cleaving the recipient DNA. Bacteriophage T4 segB gene, which is located in a cluster of tRNA genes, encodes a protein of unknown function, homologous to homing endonucleases of the GIY-YIG family. We demonstrate that SegB protein is a site-specific endonuclease, which produces mostly 3′ 2-nt protruding ends at its DNA cleavage site. Analysis of SegB cleavage sites suggests that SegB recognizes a 27-bp sequence. It contains 11-bp conserved sequence, which corresponds to a conserved motif of tRNA TψC stem-loop, whereas the remainder of the recognition site is rather degenerate. T4-related phages T2L, RB1 and RB3 contain tRNA gene regions that are homologous to that of phage T4 but lack segB gene and several tRNA genes. In co-infections of phages T4 and T2L, segB gene is inherited with nearly 100% of efficiency. The preferred inheritance depends absolutely on the segB gene integrity and is accompanied by the loss of the T2L tRNA gene region markers. We suggest that SegB is a homing endonuclease that functions to ensure spreading of its own gene and the surrounding tRNA genes among T4-related phages.
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Affiliation(s)
- Vera S Brok-Volchanskaya
- Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, Nauki ave., 5, Pushchino, Moscow, Russia
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48
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Chien MF, Huang CC, Kusano T, Endo G. Facilities for transcription and mobilization of an exon-less bacterial group II intron nested in transposon TnMERI1. Gene 2008; 408:164-71. [DOI: 10.1016/j.gene.2007.10.032] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2007] [Revised: 10/17/2007] [Accepted: 10/24/2007] [Indexed: 10/22/2022]
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49
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Murugaiah AMS, Wallinder C, Mahalingam AK, Wu X, Wan Y, Plouffe B, Botros M, Karlén A, Hallberg M, Gallo-Payet N, Alterman M. Selective angiotensin II AT2 receptor agonists devoid of the imidazole ring system. Bioorg Med Chem 2007; 15:7166-83. [PMID: 17825570 DOI: 10.1016/j.bmc.2007.07.026] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2007] [Revised: 06/28/2007] [Accepted: 07/06/2007] [Indexed: 11/19/2022]
Abstract
A versatile parallel synthetic method to obtain three series of non-cyclic analogues of the first drug-like selective angiotensin II AT(2) receptor agonist (1) has been developed. In analogy with the transformation of losartan to valsartan it was demonstrated that a non-cyclic moiety could be employed as an imidazole replacement to obtain AT(2) selective compounds. In all the three series, AT(2) receptor ligands with affinities in the lower nanomolar range were found. None of the analogues exhibited any affinity for the AT(1) receptor. Four compounds, 17, 22, 39 and 51, were examined in a neurite outgrowth cell assay. All four compounds were found to exert a high agonistic effect as deduced from their capacity to induce neurite elongation in neuronal cells, as does angiotensin II.
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Affiliation(s)
- A M S Murugaiah
- Department of Medicinal Chemistry, BMC, Uppsala University, PO Box 574, SE-751 23 Uppsala, Sweden
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Scalley-Kim M, McConnell-Smith A, Stoddard BL. Coevolution of a homing endonuclease and its host target sequence. J Mol Biol 2007; 372:1305-19. [PMID: 17720189 PMCID: PMC2040299 DOI: 10.1016/j.jmb.2007.07.052] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2007] [Revised: 07/20/2007] [Accepted: 07/24/2007] [Indexed: 12/22/2022]
Abstract
We have determined the specificity profile of the homing endonuclease I-AniI and compared it to the conservation of its host gene. Homing endonucleases are encoded within intervening sequences such as group I introns. They initiate the transfer of such elements by cleaving cognate alleles lacking the intron, leading to their transfer via homologous recombination. Each structural homing endonuclease family has arrived at an appropriate balance of specificity and fidelity that avoids toxicity while maximizing target recognition and invasiveness. I-AniI recognizes a strongly conserved target sequence in a host gene encoding apocytochrome B and has fine-tuned its specificity to correlate with wobble versus nonwobble positions across that sequence and to the amount of degeneracy inherent in individual codons. The physiological target site in the host gene is not the optimal substrate for recognition and cleavage: at least one target variant identified during a screen is bound more tightly and cleaved more rapidly. This is a result of the periodic cycle of intron homing, which at any time can present nonoptimal combinations of endonuclease specificity and insertion site sequences in a biological host.
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Affiliation(s)
- Michelle Scalley-Kim
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave. N. A3-023, Seattle WA 98109
| | - Audrey McConnell-Smith
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave. N. A3-023, Seattle WA 98109
- Graduate Program in Molecular and Cellular Biology, University of Washington Seattle, WA 98105
| | - Barry L. Stoddard
- * To whom correspondence should be addressed 1-206-667-4031 (ph) -6877 (fax),
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