1
|
Wang R, Meng Q, Wang X, Xiao Y, Sun R, Zhang Z, Fu Y, Di Giuseppe G, Liang A. Comparative genomic analysis of symbiotic and free-living Fluviibacter phosphoraccumulans strains provides insights into the evolutionary origins of obligate Euplotes-bacterial endosymbioses. Appl Environ Microbiol 2024; 90:e0190023. [PMID: 38334408 PMCID: PMC10952467 DOI: 10.1128/aem.01900-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Accepted: 01/12/2024] [Indexed: 02/10/2024] Open
Abstract
Endosymbiosis is a widespread and important phenomenon requiring diverse model systems. Ciliates are a widespread group of protists that often form symbioses with diverse microorganisms. Endosymbioses between the ciliate Euplotes and heritable bacterial symbionts are common in nature, and four essential symbionts were described: Polynucleobacter necessarius, "Candidatus Protistobacter heckmanni," "Ca. Devosia symbiotica," and "Ca. Devosia euplotis." Among them, only the genus Polynucleobacter comprises very close free-living and symbiotic representatives, which makes it an excellent model for investigating symbiont replacements and recent symbioses. In this article, we characterized a novel endosymbiont inhabiting the cytoplasm of Euplotes octocarinatus and found that it is a close relative of the free-living bacterium Fluviibacter phosphoraccumulans (Betaproteobacteria and Rhodocyclales). We present the complete genome sequence and annotation of the symbiotic Fluviibacter. Comparative analyses indicate that the genome of symbiotic Fluviibacter is small in size and rich in pseudogenes when compared with free-living strains, which seems to fit the prediction for recently established endosymbionts undergoing genome erosion. Further comparative analysis revealed reduced metabolic capacities in symbiotic Fluviibacter, which implies that the symbiont relies on the host Euplotes for carbon sources, organic nitrogen and sulfur, and some cofactors. We also estimated substitution rates between symbiotic and free-living Fluviibacter pairs for 233 genes; the results showed that symbiotic Fluviibacter displays higher dN/dS mean value than free-living relatives, which suggested that genetic drift is the main driving force behind molecular evolution in endosymbionts. IMPORTANCE In the long history of symbiosis research, most studies focused mainly on organelles or bacteria within multicellular hosts. The single-celled protists receive little attention despite harboring an immense diversity of symbiotic associations with bacteria and archaea. One subgroup of the ciliate Euplotes species is strictly dependent on essential symbionts for survival and has emerged as a valuable model for understanding symbiont replacements and recent symbioses. However, almost all of our knowledge about the evolution and functions of Euplotes symbioses comes from the Euplotes-Polynucleobacter system. In this article, we report a novel essential symbiont, which also has very close free-living relatives. Genome analysis indicated that it is a recently established endosymbiont undergoing genome erosion and relies on the Euplotes host for many essential molecules. Our results provide support for the notion that essential symbionts of the ciliate Euplotes evolve from free-living progenitors in the natural water environment.
Collapse
Affiliation(s)
- Ruanlin Wang
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan, China
| | - Qingyao Meng
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan, China
| | - Xue Wang
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan, China
| | - Yu Xiao
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan, China
| | - Ruijuan Sun
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan, China
| | - Zhiyun Zhang
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan, China
| | - Yuejun Fu
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan, China
| | | | - Aihua Liang
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan, China
| |
Collapse
|
2
|
Xiao Y, Li J, Wang R, Fan Y, Han X, Fu Y, Alepuz P, Wang W, Liang A. eIF5A promotes +1 programmed ribosomal frameshifting in Euplotes octocarinatus. Int J Biol Macromol 2024; 254:127743. [PMID: 38287569 DOI: 10.1016/j.ijbiomac.2023.127743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Revised: 10/25/2023] [Accepted: 10/26/2023] [Indexed: 01/31/2024]
Abstract
Programmed ribosomal frameshifting (PRF) exists in all branches of life that regulate gene expression at the translational level. The single-celled eukaryote Euplotes exhibit high frequency of PRF. However, the molecular mechanism of modulating Euplotes PRF remains largely unknown. Here, we identified two novel eIF5A genes, eIF5A1 and eIF5A2, in Euplotes octocarinatus and found that the Eo-eIF5A2 gene requires a -1 PRF to produce complete protein product. Although both Eo-eIF5As showed significant structural similarity with yeast eIF5A, neither of them could functionally replace yeast eIF5A. Eo-eIF5A knockdown inhibited +1 PRF of the η-tubulin gene. Using an in vitro reconstituted translation system, we found that hypusinated Eo-eIF5A (Eo-eIF5AH) can promote +1 PRF at the canonical AAA_UAA frameshifting site of Euplotes. The results showed eIF5A is a novel trans-regulator of PRF in Euplotes and has an evolutionary conserved role in regulating +1 PRF in eukaryotes.
Collapse
Affiliation(s)
- Yu Xiao
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China
| | - Jia Li
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China
| | - Ruanlin Wang
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China.
| | - Yajiao Fan
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China
| | - Xiaxia Han
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China
| | - Yuejun Fu
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China
| | - Paula Alepuz
- Instituto de Biotecnología y Biomedicina (Biotecmed) and Departamento de Bioquímica y Biología Molecular, Universitat de València, Spain
| | - Wei Wang
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China.
| | - Aihua Liang
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China.
| |
Collapse
|
3
|
Candelori A, Di Giuseppe G, Villalobo E, Sjödin A, Vallesi A. Bipolar Biogeographical Distribution of Parafrancisella Bacteria Carried by the Ciliate Euplotes. Microb Ecol 2023; 86:3128-3132. [PMID: 37433980 DOI: 10.1007/s00248-023-02263-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Accepted: 07/05/2023] [Indexed: 07/13/2023]
Abstract
Parafrancisella adeliensis, a Francisella-like endosymbiont, was found to reside in the cytoplasm of an Antarctic strain of the bipolar ciliate species, Euplotes petzi. To inquire whether Euplotes cells collected from distant Arctic and peri-Antarctic sites host Parafrancisella bacteria, wild-type strains of the congeneric bipolar species, E. nobilii, were screened for Parafrancisella by in situ hybridization and 16S gene amplification and sequencing. Results indicate that all Euplotes strains analyzed contained endosymbiotic bacteria with 16S nucleotide sequences closely similar to the P. adeliensis 16S gene sequence. This finding suggests that Parafrancisella/Euplotes associations are not endemic to Antarctica, but are common in both the Antarctic and Arctic regions.
Collapse
Affiliation(s)
- Annalisa Candelori
- School of Biosciences and Veterinary Medicine, University of Camerino, Camerino, MC, Italy
| | | | - Eduardo Villalobo
- Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Seville, Spain
| | - Andreas Sjödin
- Division of CBRN Security and Defense, FOI - Swedish Defense Research Agency, Umeå, Sweden
| | - Adriana Vallesi
- School of Biosciences and Veterinary Medicine, University of Camerino, Camerino, MC, Italy.
| |
Collapse
|
4
|
Gaydukova SA, Moldovan MA, Vallesi A, Heaphy SM, Atkins JF, Gelfand MS, Baranov PV. Nontriplet feature of genetic code in Euplotes ciliates is a result of neutral evolution. Proc Natl Acad Sci U S A 2023; 120:e2221683120. [PMID: 37216548 PMCID: PMC10235951 DOI: 10.1073/pnas.2221683120] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Accepted: 04/12/2023] [Indexed: 05/24/2023] Open
Abstract
The triplet nature of the genetic code is considered a universal feature of known organisms. However, frequent stop codons at internal mRNA positions in Euplotes ciliates ultimately specify ribosomal frameshifting by one or two nucleotides depending on the context, thus posing a nontriplet feature of the genetic code of these organisms. Here, we sequenced transcriptomes of eight Euplotes species and assessed evolutionary patterns arising at frameshift sites. We show that frameshift sites are currently accumulating more rapidly by genetic drift than they are removed by weak selection. The time needed to reach the mutational equilibrium is several times longer than the age of Euplotes and is expected to occur after a several-fold increase in the frequency of frameshift sites. This suggests that Euplotes are at an early stage of the spread of frameshifting in expression of their genome. In addition, we find the net fitness burden of frameshift sites to be noncritical for the survival of Euplotes. Our results suggest that fundamental genome-wide changes such as a violation of the triplet character of genetic code can be introduced and maintained solely by neutral evolution.
Collapse
Affiliation(s)
- Sofya A. Gaydukova
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow199911, Russia
| | - Mikhail A. Moldovan
- A. A. Kharkevich Institute for Information Transmission Problems RAS, Moscow127051, Russia
| | - Adriana Vallesi
- Laboratory of Eukaryotic Microbiology and Animal Biology, School of Biosciences and Veterinary Medicine, University of Camerino, Camerino62032, Italy
| | - Stephen M. Heaphy
- School of Biochemistry and Cell Biology, University College Cork, CorkT12 XF62, Ireland
| | - John F. Atkins
- School of Biochemistry and Cell Biology, University College Cork, CorkT12 XF62, Ireland
- Department of Human Genetics, University of Utah, Salt Lake City, UT84112
| | - Mikhail S. Gelfand
- A. A. Kharkevich Institute for Information Transmission Problems RAS, Moscow127051, Russia
| | - Pavel V. Baranov
- School of Biochemistry and Cell Biology, University College Cork, CorkT12 XF62, Ireland
| |
Collapse
|
5
|
Somasundaram S, Abraham JS, Maurya S, Toteja R, Gupta R, Makhija S. Molecular characterization and transcriptional modulation of stress-responsive genes under heavy metal stress in freshwater ciliate, Euplotes aediculatus. Ecotoxicology 2022; 31:271-288. [PMID: 34982303 DOI: 10.1007/s10646-021-02518-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 12/24/2021] [Indexed: 06/14/2023]
Abstract
Heavy metal pollutants in the environment are increasing exponentially due to various anthropogenic factors including mining, industrial and agricultural wastes. Living organisms exposed to heavy metals above a certain threshold level induces deleterious effects in these organisms. To live in such severe environments, microbes have developed a range of tolerance mechanisms which include upregulation of stress-responsive genes and/or antioxidant enzymes to detoxify the metal stress. Single cell eukaryotic microorganisms, i.e., ciliates, are highly sensitive to environmental pollutants mainly due to the absence of cell wall, which make them suitable candidates for conducting ecotoxicological studies. Therefore, the present investigation describes the effects of heavy metals (cadmium and copper) on freshwater ciliate, Euplotes aediculatus. The activities of antioxidant enzymes, i.e., catalase and glutathione peroxidase in E. aediculatus were determined under heavy metal exposure. Besides, the expression of stress-responsive genes, namely, heat-shock protein 70 (hsp70) and catalase (cat), has also been determined in this freshwater ciliate species under metal stress. The present study showed that the enzyme activity and the expression of these genes increased with an increase in the heavy metal concentration and with the duration of metal exposure. Also, these stress-responsive genes were sequenced and characterized to comprehend their role in cell rescue.
Collapse
Affiliation(s)
- Sripoorna Somasundaram
- Ciliate Biology Laboratory, Acharya Narendra Dev College, University of Delhi, Delhi, India
| | - Jeeva Susan Abraham
- Ciliate Biology Laboratory, Acharya Narendra Dev College, University of Delhi, Delhi, India
| | - Swati Maurya
- Ciliate Biology Laboratory, Acharya Narendra Dev College, University of Delhi, Delhi, India
| | - Ravi Toteja
- Ciliate Biology Laboratory, Acharya Narendra Dev College, University of Delhi, Delhi, India
| | - Renu Gupta
- Zoology Department, Maitreyi College, University of Delhi, Delhi, India
| | - Seema Makhija
- Ciliate Biology Laboratory, Acharya Narendra Dev College, University of Delhi, Delhi, India.
| |
Collapse
|
6
|
Zou S, Fu R, Deng H, Zhang Q, Gentekaki E, Gong J. Coupling between Ribotypic and Phenotypic Traits of Protists across Life Cycle Stages and Temperatures. Microbiol Spectr 2021; 9:e0173821. [PMID: 34817220 PMCID: PMC8612162 DOI: 10.1128/spectrum.01738-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Accepted: 10/16/2021] [Indexed: 01/04/2023] Open
Abstract
Relationships between ribotypic and phenotypic traits of protists across life cycle stages remain largely unknown. Herein, we used single cells of two soil and two marine ciliate species to examine phenotypic and ribotypic traits and their relationships across lag, log, plateau, cystic stages and temperatures. We found that Colpoda inflata and Colpoda steinii demonstrated allometric relationships between 18S ribosomal DNA (rDNA) copy number per cell (CNPC), cell volume (CV), and macronuclear volume across all life cycle stages. Integrating previously reported data of Euplotes vannus and Strombidium sulcatum indicated taxon-dependent rDNA CNPC-CV functions. Ciliate and prokaryote data analysis revealed that the rRNA CNPC followed a unified power-law function only if the rRNA-deficient resting cysts were not considered. Hence, a theoretical framework was proposed to estimate the relative quantity of resting cysts in the protistan populations with total cellular rDNA and rRNA copy numbers. Using rDNA CNPC was a better predictor of growth rate at a given temperature than rRNA CNPC and CV, suggesting replication of redundant rDNA operons as a key factor that slows cell division. Single-cell high-throughput sequencing and analysis after correcting sequencing errors revealed multiple rDNA and rRNA variants per cell. Both encystment and temperature affected the number of rDNA and rRNA variants in several cases. The divergence of rDNA and rRNA sequence in a single cell ranged from 1% to 10% depending on species. These findings have important implications for inferring cell-based biological traits (e.g., species richness, abundance and biomass, activity, and community structure) of protists using molecular approaches. IMPORTANCE Based on phenotypic traits, traditional surveys usually characterize organismal richness, abundance, biomass, and growth potential to describe diversity, organization, and function of protistan populations and communities. The rRNA gene (rDNA) and its transcripts have been widely used as molecular markers in ecological studies of protists. Nevertheless, the manner in which these molecules relate to cellular (organismal) and physiological traits remains poorly understood, which could lead to misinterpretations of protistan diversity and ecology. The current research highlights the dynamic nature of cellular rDNA and rRNA contents, which tightly couple with multiple phenotypic traits in ciliated protists. We demonstrate that quantity of resting cysts and maximum growth rate of a population can be theoretically estimated using ribotypic trait-based models. The intraindividual sequence polymorphisms of rDNA and rRNA can be influenced by encystment and temperature, which should be considered when interpreting species-level diversity and community structure of microbial eukaryotes.
Collapse
Affiliation(s)
- Songbao Zou
- Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, China
- University of Chinese Academy of Sciences, Beijing, China
- Key Laboratory of Healthy Freshwater Aquaculture, Ministry of Agriculture and Rural Affairs, Huzhou, China
- Key Laboratory of Fish Health and Nutrition of Zhejiang Province, Zhejiang Institute of Freshwater Fisheries, Huzhou, China
| | - Rao Fu
- Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, China
- University of Chinese Academy of Sciences, Beijing, China
- Shandong Institute of Sericulture, Shandong Academy of Agricultural Sciences, Yantai, China
| | - Huiwen Deng
- School of Marine Sciences, Sun Yat-sen University, Zhuhai, China
- Southern Marine Science and Engineering Guangdong Laboratory, Zhuhai, China
| | - Qianqian Zhang
- Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Eleni Gentekaki
- School of Science, Mae Fah Luang University, Chiang Rai, Thailand
| | - Jun Gong
- School of Marine Sciences, Sun Yat-sen University, Zhuhai, China
- Southern Marine Science and Engineering Guangdong Laboratory, Zhuhai, China
| |
Collapse
|
7
|
Mozzicafreddo M, Pucciarelli S, Swart EC, Piersanti A, Emmerich C, Migliorelli G, Ballarini P, Miceli C. The macronuclear genome of the Antarctic psychrophilic marine ciliate Euplotes focardii reveals new insights on molecular cold adaptation. Sci Rep 2021; 11:18782. [PMID: 34548559 PMCID: PMC8455672 DOI: 10.1038/s41598-021-98168-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 09/05/2021] [Indexed: 11/23/2022] Open
Abstract
The macronuclear (MAC) genomes of ciliates belonging to the genus Euplotes species are comprised of numerous small DNA molecules, nanochromosomes, each typically encoding a single gene. These genomes are responsible for all gene expression during vegetative cell growth. Here, we report the analysis of the MAC genome from the Antarctic psychrophile Euplotes focardii. Nanochromosomes containing bacterial sequences were not found, suggesting that phenomena of horizontal gene transfer did not occur recently, even though this ciliate species has a substantial associated bacterial consortium. As in other euplotid species, E. focardii MAC genes are characterized by a high frequency of translational frameshifting. Furthermore, in order to characterize differences that may be consequent to cold adaptation and defense to oxidative stress, the main constraints of the Antarctic marine microorganisms, we compared E. focardii MAC genome with those available from mesophilic Euplotes species. We focussed mainly on the comparison of tubulin, antioxidant enzymes and heat shock protein (HSP) 70 families, molecules which possess peculiar characteristic correlated with cold adaptation in E. focardii. We found that α-tubulin genes and those encoding SODs and CATs antioxidant enzymes are more numerous than in the mesophilic Euplotes species. Furthermore, the phylogenetic trees showed that these molecules are divergent in the Antarctic species. In contrast, there are fewer hsp70 genes in E. focardii compared to mesophilic Euplotes and these genes do not respond to thermal stress but only to oxidative stress. Our results suggest that molecular adaptation to cold and oxidative stress in the Antarctic environment may not only be due to particular amino acid substitutions but also due to duplication and divergence of paralogous genes.
Collapse
Affiliation(s)
- Matteo Mozzicafreddo
- School of Biosciences and Veterinary Medicine, University of Camerino, 62032, Camerino, MC, Italy.
| | - Sandra Pucciarelli
- School of Biosciences and Veterinary Medicine, University of Camerino, 62032, Camerino, MC, Italy
| | - Estienne C Swart
- Max Planck Institute for Developmental Biology, Tübingen, Germany
| | - Angela Piersanti
- School of Biosciences and Veterinary Medicine, University of Camerino, 62032, Camerino, MC, Italy
| | | | - Giovanna Migliorelli
- School of Biosciences and Veterinary Medicine, University of Camerino, 62032, Camerino, MC, Italy
| | - Patrizia Ballarini
- School of Biosciences and Veterinary Medicine, University of Camerino, 62032, Camerino, MC, Italy
| | - Cristina Miceli
- School of Biosciences and Veterinary Medicine, University of Camerino, 62032, Camerino, MC, Italy
| |
Collapse
|
8
|
Yang G, Mozzicafreddo M, Ballarini P, Pucciarelli S, Miceli C. An In-Silico Comparative Study of Lipases from the Antarctic Psychrophilic Ciliate Euplotes focardii and the Mesophilic Congeneric Species Euplotes crassus: Insight into Molecular Cold-Adaptation. Mar Drugs 2021; 19:md19020067. [PMID: 33513970 PMCID: PMC7912073 DOI: 10.3390/md19020067] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 01/23/2021] [Accepted: 01/25/2021] [Indexed: 11/30/2022] Open
Abstract
Cold-adapted enzymes produced by psychrophilic organisms have elevated catalytic activities at low temperatures compared to their mesophilic counterparts. This is largely due to amino acids changes in the protein sequence that often confer increased molecular flexibility in the cold. Comparison of structural changes between psychrophilic and mesophilic enzymes often reveal molecular cold adaptation. In the present study, we performed an in-silico comparative analysis of 104 hydrolytic enzymes belonging to the family of lipases from two evolutionary close marine ciliate species: The Antarctic psychrophilic Euplotes focardii and the mesophilic Euplotes crassus. By applying bioinformatics approaches, we compared amino acid composition and predicted secondary and tertiary structures of these lipases to extract relevant information relative to cold adaptation. Our results not only confirm the importance of several previous recognized amino acid substitutions for cold adaptation, as the preference for small amino acid, but also identify some new factors correlated with the secondary structure possibly responsible for enhanced enzyme activity at low temperatures. This study emphasizes the subtle sequence and structural modifications that may help to transform mesophilic into psychrophilic enzymes for industrial applications by protein engineering.
Collapse
|
9
|
Serra V, Gammuto L, Nitla V, Castelli M, Lanzoni O, Sassera D, Bandi C, Sandeep BV, Verni F, Modeo L, Petroni G. Morphology, ultrastructure, genomics, and phylogeny of Euplotes vanleeuwenhoeki sp. nov. and its ultra-reduced endosymbiont "Candidatus Pinguicoccus supinus" sp. nov. Sci Rep 2020; 10:20311. [PMID: 33219271 PMCID: PMC7679464 DOI: 10.1038/s41598-020-76348-z] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Accepted: 09/30/2020] [Indexed: 01/30/2023] Open
Abstract
Taxonomy is the science of defining and naming groups of biological organisms based on shared characteristics and, more recently, on evolutionary relationships. With the birth of novel genomics/bioinformatics techniques and the increasing interest in microbiome studies, a further advance of taxonomic discipline appears not only possible but highly desirable. The present work proposes a new approach to modern taxonomy, consisting in the inclusion of novel descriptors in the organism characterization: (1) the presence of associated microorganisms (e.g.: symbionts, microbiome), (2) the mitochondrial genome of the host, (3) the symbiont genome. This approach aims to provide a deeper comprehension of the evolutionary/ecological dimensions of organisms since their very first description. Particularly interesting, are those complexes formed by the host plus associated microorganisms, that in the present study we refer to as "holobionts". We illustrate this approach through the description of the ciliate Euplotes vanleeuwenhoeki sp. nov. and its bacterial endosymbiont "Candidatus Pinguicoccus supinus" gen. nov., sp. nov. The endosymbiont possesses an extremely reduced genome (~ 163 kbp); intriguingly, this suggests a high integration between host and symbiont.
Collapse
Affiliation(s)
- Valentina Serra
- Department of Biology, University of Pisa, Via Volta 4/6, 56126, Pisa, Italy
| | - Leandro Gammuto
- Department of Biology, University of Pisa, Via Volta 4/6, 56126, Pisa, Italy
| | - Venkatamahesh Nitla
- Department of Biology, University of Pisa, Via Volta 4/6, 56126, Pisa, Italy
| | - Michele Castelli
- Department of Biosciences, Romeo and Enrica Invernizzi Pediatric Research Center, University of Milan, Milan, Italy
- Department of Biology and Biotechnology "Lazzaro Spallanzani", Pavia University, Pavia, Italy
| | - Olivia Lanzoni
- Department of Biology, University of Pisa, Via Volta 4/6, 56126, Pisa, Italy
| | - Davide Sassera
- Department of Biology and Biotechnology "Lazzaro Spallanzani", Pavia University, Pavia, Italy
| | - Claudio Bandi
- Department of Biosciences, Romeo and Enrica Invernizzi Pediatric Research Center, University of Milan, Milan, Italy
| | | | - Franco Verni
- Department of Biology, University of Pisa, Via Volta 4/6, 56126, Pisa, Italy
| | - Letizia Modeo
- Department of Biology, University of Pisa, Via Volta 4/6, 56126, Pisa, Italy.
- CIME, Centro Interdipartimentale di Microscopia Elettronica, Università di Pisa, Pisa, Italy.
- CISUP, Centro per l'Integrazione della Strumentazione dell'Università di Pisa, Pisa, India.
| | - Giulio Petroni
- Department of Biology, University of Pisa, Via Volta 4/6, 56126, Pisa, Italy.
- CIME, Centro Interdipartimentale di Microscopia Elettronica, Università di Pisa, Pisa, Italy.
- CISUP, Centro per l'Integrazione della Strumentazione dell'Università di Pisa, Pisa, India.
| |
Collapse
|
10
|
Pischedda A, Ramasamy KP, Mangiagalli M, Chiappori F, Milanesi L, Miceli C, Pucciarelli S, Lotti M. Antarctic marine ciliates under stress: superoxide dismutases from the psychrophilic Euplotes focardii are cold-active yet heat tolerant enzymes. Sci Rep 2018; 8:14721. [PMID: 30283056 PMCID: PMC6170424 DOI: 10.1038/s41598-018-33127-1] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 09/20/2018] [Indexed: 11/09/2022] Open
Abstract
Oxidative stress is a particularly severe threat to Antarctic marine polar organisms because they are exposed to high dissolved oxygen and to intense UV radiation. This paper reports the features of three superoxide dismutases from the Antarctic psychrophilic ciliate Euplotes focardii that faces two environmental challenges, oxidative stress and low temperature. Two out of these are Cu,Zn superoxide dismutases (named Ef-SOD1a and Ef-SOD1b) and one belongs to the Mn-containing group (Ef-SOD2). Ef-SOD1s and Ef-SOD2 differ in their evolutionary history, expression and overall structural features. Ef-SOD1 genes are expressed at different levels, with Ef-SOD1b mRNA 20-fold higher at the ciliate optimal temperature of growth (4 °C). All Ef-SOD enzymes are active at 4 °C, consistent with the definition of cold-adapted enzymes. At the same time, they display temperatures of melting in the range 50-70 °C and retain residual activity after incubation at 65-75 °C. Supported by data of molecular dynamics simulation, we conclude that the E. focardii SODs combine cold activity, local molecular flexibility and thermo tolerance.
Collapse
Affiliation(s)
- Alessandro Pischedda
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Piazza della Scienza 2, 20126, Milano, Italy
| | - Kesava Priyan Ramasamy
- School of Biosciences and Veterinary Medicine, University of Camerino, Via Gentile III da Varano, 1, 62032, Camerino (MC), Italy
| | - Marco Mangiagalli
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Piazza della Scienza 2, 20126, Milano, Italy
| | | | | | - Cristina Miceli
- School of Biosciences and Veterinary Medicine, University of Camerino, Via Gentile III da Varano, 1, 62032, Camerino (MC), Italy
| | - Sandra Pucciarelli
- School of Biosciences and Veterinary Medicine, University of Camerino, Via Gentile III da Varano, 1, 62032, Camerino (MC), Italy.
| | - Marina Lotti
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Piazza della Scienza 2, 20126, Milano, Italy
| |
Collapse
|
11
|
Chen F, Xue Y, Pan N, Bhatti MZ, Niu T, Chen J. New contribution to the morphology and molecular mechanism of Euplotes encysticus encystment. Sci Rep 2018; 8:12795. [PMID: 30143743 PMCID: PMC6109176 DOI: 10.1038/s41598-018-31160-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Accepted: 08/13/2018] [Indexed: 11/30/2022] Open
Abstract
Ciliated protists are a large group of single-cell eukaryotes, leading to the resting cysts in unfavorable environmental condition. However, the underlying molecular mechanism of encystment in the free-living ciliates is poorly understood. Here we show that the resting cysts are better than the vegetative cells of Euplotes encysticus in adverse survivor with respect to energy metabolism. Therefore scale identification of encystment-related proteins in Euplotes encysticus was investigated by iTRAQ analysis. We analyzed a total of 130 proteins, in which 19 proteins involving 12 upregulated and 7 downregulated proteins were associated with encystment in the resting cysts in comparison with the vegetative cells. Moreover, direct fluorescent labeling analysis showed that the vegetative cells treated with shRNA-β-tubulin recombinant E. coli accumulated a large number of granular materials, and dramatic cell morphology changes. Importantly, the cell membrane rupture phenomenon was observed after three weeks of shRNA-β-tubulin interference as compared to the control group. These results revealed that different proteins might play an important role in the process of the vegetative cells into the resting cysts. These results will help to reveal the morphological changes and molecular mechanism of resting cyst formation of ciliates.
Collapse
Affiliation(s)
- Fenfen Chen
- School of Life Sciences, East China Normal University, Shanghai, 200241, P. R. China
| | - Yanyan Xue
- School of Life Sciences, East China Normal University, Shanghai, 200241, P. R. China
| | - Nan Pan
- School of Life Sciences, East China Normal University, Shanghai, 200241, P. R. China
| | - Muhammad Zeeshan Bhatti
- Institute of Biomedical Sciences, School of Life Sciences, East China Normal University, Shanghai, 200241, P. R. China
- Department of Molecular Medicine, National University of Medical Sciences, Rawalpindi, Pakistan
| | - Tao Niu
- School of Life Sciences, East China Normal University, Shanghai, 200241, P. R. China
| | - Jiwu Chen
- School of Life Sciences, East China Normal University, Shanghai, 200241, P. R. China.
| |
Collapse
|
12
|
Kim JS, Kim H, Yim B, Rhee JS, Won EJ, Lee YM. Identification and molecular characterization of two Cu/Zn-SODs and Mn-SOD in the marine ciliate Euplotes crassus: Modulation of enzyme activity and transcripts in response to copper and cadmium. Aquat Toxicol 2018; 199:296-304. [PMID: 29605288 DOI: 10.1016/j.aquatox.2018.03.020] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Revised: 03/12/2018] [Accepted: 03/17/2018] [Indexed: 06/08/2023]
Abstract
The superoxide dismutase (SOD) family is a first line antioxidant enzyme group involved in transformation of the superoxide anion (O2-) into hydrogen peroxide (H2O2) and O2. SOD gene expression patterns and enzyme activities therefore have a role as molecular biomarkers in evaluating the oxidative stress status of aquatic organisms. However, antioxidant enzyme systems are yet to be fully explored in the marine ciliates. In this study, we identified and characterized two types of Cu/Zn SODs (Ec-Cu/ZnSOD1 and Ec-Cu/ZnSOD2) and Ec-Mn SOD in the marine ciliate Euplotes crassus. Subsequently, SOD activity and transcriptional modulation of the relevant genes were investigated after the exposure to Cd and Cu for 8 h. All Ec-SODs showed conserved domains and metal binding sites on their active sites. Total SOD activity was induced at 1 h after exposure to Cd (125 and 1000 μg/L), and showed a marginal increase at 1-h exposure to Cu (10 and 100 μg/L). However, SOD activity was maintained at a steady level under Cd and decreased under Cu exposure conditions at 3 h and 8 h. mRNA expression of both the Ec-Cu/Zn-SODs and Mn-SOD were remarkably elevated after the exposure to Cd (250-1000 μg/L, maximum 4-fold, p < 0.05) and, in particular, Cu (25-100 μg/L, maximum > 20-fold, p < 0.05), in a concentration - dependent manner. These findings suggest that Ec-SODs may be actively involved in cellular protection against metal - mediated oxidative stress. This study is therefore helpful in understanding the molecular responses for metal toxicity in the ciliates.
Collapse
Affiliation(s)
- Ji-Soo Kim
- Biosafety Research Team, Environmental Health Research Department, National Institute of Environmental Research, Kyungseo-Dong, Seo-gu, Incheon 22689, Republic of Korea
| | - Hokyun Kim
- Risk Assessment Division, National Institute of Environmental Research, Kyungseo-Dong, Seo-gu, Incheon 22689, Republic of Korea
| | - Bora Yim
- Department of Life Science, College of Natural Sciences, Sangmyung University, Seoul 03016, Republic of Korea
| | - Jae-Sung Rhee
- Department of Marine Science, College of Natural Sciences, Incheon National University, Incheon 22012, Republic of Korea
| | - Eun-Ji Won
- Department of Marine Science and Convergent Technology, Hanyang University, Ansan 15588, Republic of Korea
| | - Young-Mi Lee
- Department of Life Science, College of Natural Sciences, Sangmyung University, Seoul 03016, Republic of Korea.
| |
Collapse
|
13
|
Kim H, Yim B, Kim J, Kim H, Lee YM. Molecular characterization of ABC transporters in marine ciliate, Euplotes crassus: Identification and response to cadmium and benzo[a]pyrene. Mar Pollut Bull 2017; 124:725-735. [PMID: 28139231 DOI: 10.1016/j.marpolbul.2017.01.046] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Revised: 01/12/2017] [Accepted: 01/24/2017] [Indexed: 06/06/2023]
Abstract
ATP-binding cassette (ABC) transporters participate in transporting various substances, including xenobiotics, in or out of cells. However, their genetic information and function in ciliates remain still unclear. In this study, we sequenced and characterized two ABC transporter genes (EcABCB and EcABCC), and investigated the effect of cadmium (Cd) and benzo[a]pyrene (B[a]P) on their function and gene expression, using efflux assay and real-time reverse transcription-polymerase chain reaction (qRT-PCR), respectively, in the marine ciliate, Euplotes crassus. Sequencing analysis and efflux assay showed that EcABCB and EcABCC are typical ABC transporters, possessing conserved function. Exposure to Cd (≥5mg/L) and B[a]P (≥50.5μg/L) enhanced accumulation of a substrate. A significant increase in the expression of EcABCB and EcABC mRNA was observed at lower concentration in response to Cd and B[a]P. Our findings indicate that Cd and B[a]P could inhibit the efflux function of ABC transporters, leading to cellular toxicity in the ciliate.
Collapse
Affiliation(s)
- Hokyun Kim
- Department of Life Science, College of Natural Sciences, Sangmyung University, Seoul 03016, South Korea
| | - Bora Yim
- Department of Life Science, College of Natural Sciences, Sangmyung University, Seoul 03016, South Korea
| | - Jisoo Kim
- Department of Life Science, College of Natural Sciences, Sangmyung University, Seoul 03016, South Korea
| | - Haeyeon Kim
- Department of Life Science, College of Natural Sciences, Sangmyung University, Seoul 03016, South Korea
| | - Young-Mi Lee
- Department of Life Science, College of Natural Sciences, Sangmyung University, Seoul 03016, South Korea.
| |
Collapse
|
14
|
Lobanov AV, Heaphy SM, Turanov AA, Gerashchenko MV, Pucciarelli S, Devaraj RR, Xie F, Petyuk VA, Smith RD, Klobutcher LA, Atkins JF, Miceli C, Hatfield DL, Baranov PV, Gladyshev VN. Position-dependent termination and widespread obligatory frameshifting in Euplotes translation. Nat Struct Mol Biol 2017; 24:61-68. [PMID: 27870834 PMCID: PMC5295771 DOI: 10.1038/nsmb.3330] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Accepted: 10/31/2016] [Indexed: 11/09/2022]
Abstract
The ribosome can change its reading frame during translation in a process known as programmed ribosomal frameshifting. These rare events are supported by complex mRNA signals. However, we found that the ciliates Euplotes crassus and Euplotes focardii exhibit widespread frameshifting at stop codons. 47 different codons preceding stop signals resulted in either +1 or +2 frameshifts, and +1 frameshifting at AAA was the most frequent. The frameshifts showed unusual plasticity and rapid evolution, and had little influence on translation rates. The proximity of a stop codon to the 3' mRNA end, rather than its occurrence or sequence context, appeared to designate termination. Thus, a 'stop codon' is not a sufficient signal for translation termination, and the default function of stop codons in Euplotes is frameshifting, whereas termination is specific to certain mRNA positions and probably requires additional factors.
Collapse
Affiliation(s)
- Alexei V. Lobanov
- Division of Genetics, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusets, USA
| | - Stephen M. Heaphy
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - Anton A. Turanov
- Division of Genetics, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusets, USA
| | - Maxim V. Gerashchenko
- Division of Genetics, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusets, USA
| | - Sandra Pucciarelli
- School of Biosciences and Biotechnology, University of Camerino, Camerino, Italy
| | - Raghul R. Devaraj
- School of Biosciences and Biotechnology, University of Camerino, Camerino, Italy
| | - Fang Xie
- Pacific Northwest National Laboratory, Richland, Washington, USA
| | | | - Richard D. Smith
- Pacific Northwest National Laboratory, Richland, Washington, USA
| | - Lawrence A. Klobutcher
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, Connecticut, USA
| | - John F. Atkins
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - Cristina Miceli
- School of Biosciences and Biotechnology, University of Camerino, Camerino, Italy
| | - Dolph L. Hatfield
- Molecular Biology of Selenium Section, Mouse Cancer Genetics Program, Center for Cancer Research, National Institutes of Health, Bethesda, Maryland, USA
| | - Pavel V. Baranov
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - Vadim N. Gladyshev
- Division of Genetics, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusets, USA
| |
Collapse
|
15
|
Syberg-Olsen MJ, Irwin NAT, Vannini C, Erra F, Di Giuseppe G, Boscaro V, Keeling PJ. Biogeography and Character Evolution of the Ciliate Genus Euplotes (Spirotrichea, Euplotia), with Description of Euplotes curdsi sp. nov. PLoS One 2016; 11:e0165442. [PMID: 27828996 PMCID: PMC5102374 DOI: 10.1371/journal.pone.0165442] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2016] [Accepted: 10/06/2016] [Indexed: 01/08/2023] Open
Abstract
Ciliates comprise a diverse and ecologically important phylum of unicellular protists. One of the most specious and best-defined genera is Euplotes, which constitutes more than 70 morphospecies, many of which have never been molecularly tested. The increasing number of described Euplotes taxa emphasizes the importance for detailed characterizations of new ones, requiring standardized morphological observations, sequencing of molecular markers and careful comparison with previous literature. Here we describe Euplotes curdsi sp. nov., distinguishable by the combination of the following features: 45–65 μm length, oval or elongated shape with both ends rounded, narrow peristome with 25–34 adoral membranelles, conspicuous paroral membrane, double-eurystomus dorsal argyrome type, 6–7 dorsolateral kineties and 10 frontoventral cirri. Three populations of the novel species have been found in brackish and marine samples in the Mediterranean and the White Sea. We provide the SSU rRNA gene sequences of these populations, and an updated phylogeny of the genus Euplotes. Using the molecular phylogenetic tree, we inferred aspects of the biogeographical history of the genus and the evolution of its most important taxonomic characters in order to provide a frame for future descriptions. Ultimately, these data reveal recurrent trends of freshwater invasion and highlight the dynamic, yet convergent, morphological evolution of Euplotes.
Collapse
Affiliation(s)
- Mitchell J. Syberg-Olsen
- Canadian Institute for Advanced Research, Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada
| | - Nicholas A. T. Irwin
- Canadian Institute for Advanced Research, Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada
| | | | - Fabrizio Erra
- Dipartimento di Biologia, Università di Pisa, Pisa, Italy
| | | | - Vittorio Boscaro
- Canadian Institute for Advanced Research, Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada
- * E-mail:
| | - Patrick J. Keeling
- Canadian Institute for Advanced Research, Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada
| |
Collapse
|
16
|
Pucciarelli S, Devaraj RR, Mancini A, Ballarini P, Castelli M, Schrallhammer M, Petroni G, Miceli C. Microbial Consortium Associated with the Antarctic Marine Ciliate Euplotes focardii: An Investigation from Genomic Sequences. Microb Ecol 2015; 70:484-97. [PMID: 25704316 PMCID: PMC4494151 DOI: 10.1007/s00248-015-0568-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Accepted: 01/08/2015] [Indexed: 05/23/2023]
Abstract
We report the characterization of the bacterial consortium associated to Euplotes focardii, a strictly psychrophilic marine ciliate that was maintained in laboratory cultures at 4 °C after its first isolation from Terra Nova Bay, in Antarctica. By Illumina genome analyser, we obtained 11,179 contigs of potential prokaryotic origin and classified them according to the NCBI's prokaryotic attributes table. The majority of these sequences correspond to either Bacteroidetes (16 %) or Proteobacteria (78 %). The latter were dominated by gamma- (39 %, including sequences related to the pathogenic genus Francisella), and alpha-proteobacterial (30 %) sequences. Analysis of the Pfam domain family and Gene Ontology term variation revealed that the most frequent terms that appear unique to this consortium correspond to proteins involved in "transmembrane transporter activity" and "oxidoreductase activity". Furthermore, we identified genes that encode for enzymes involved in the catabolism of complex substance for energy reserves. We also characterized members of the transposase and integrase superfamilies, whose role in bacterial evolution is well documented, as well as putative antifreeze proteins. Antibiotic treatments of E. focardii cultures delayed the cell division of the ciliate. To conclude, our results indicate that this consortium is largely represented by bacteria derived from the original Antarctic sample and may contribute to the survival of E. focardii in laboratory condition. Furthermore, our results suggest that these bacteria may have a more general role in E. focardii survival in its natural cold and oxidative environment.
Collapse
Affiliation(s)
- Sandra Pucciarelli
- School of Biosciences and Veterinary Medicine, University of Camerino, Camerino, 62032, Italy,
| | | | | | | | | | | | | | | |
Collapse
|
17
|
Hong Y, Liu S, Lin X, Li J, Yi Z, Al-Rasheid KAS. Recognizing the importance of exposure-dose-response dynamics for ecotoxicity assessment: nitrofurazone-induced antioxidase activity and mRNA expression in model protozoan Euplotes vannus. Environ Sci Pollut Res Int 2015; 22:9544-9553. [PMID: 25628113 DOI: 10.1007/s11356-015-4096-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2014] [Accepted: 01/08/2015] [Indexed: 06/04/2023]
Abstract
The equivocality of dose-response relationships has, in practice, hampered the application of biomarkers as a means to evaluate environmental risk, yet this important issue has not yet been fully recognized or explored. This paper evaluates the potential of antioxidant enzymes in the ciliated protozoan Euplotes vannus for use as biomarkers. Dose-response dynamics, together with both the enzyme activity and the gene expression of the antioxidant enzymes, superoxide dismutase, and glutathione peroxidase, were investigated when E. vannus were exposed to graded doses of nitrofurazone for several discrete durations. Mathematical models were explored to characterize the dose-response profiles and, specifically, to identify any equivocality in terms of endpoint. Significant differences were found in both enzyme activity and messenger RNA (mRNA) expression in the E. vannus treated with nitrofurazone, and the interactions between exposure dosage and duration were significant. Correlations between enzyme activity, mRNA expression, and nitrofurazone dose varied with exposure duration. Particularly, the dose-responses showed different dynamics depending on either endpoint or exposure duration. Our findings suggest that both the enzyme activity and the gene expression of the tested antioxidant enzymes can be used as biomarkers for ecotoxicological assessment on the premise of ascertaining appropriate dosage scope, exposure duration, endpoint, etc., which can be achieved by using dose-response dynamics.
Collapse
Affiliation(s)
- Yazhen Hong
- Key Laboratory of Ecology and Environmental Science in Guangdong Higher Education, College of Life Science, South China Normal University, Guangzhou, 510631, Guangdong, China
| | | | | | | | | | | |
Collapse
|
18
|
Kim SH, Kim SJ, Lee JS, Lee YM. Acute effects of heavy metals on the expression of glutathione-related antioxidant genes in the marine ciliate Euplotes crassus. Mar Pollut Bull 2014; 85:455-462. [PMID: 24882442 DOI: 10.1016/j.marpolbul.2014.05.025] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Revised: 04/29/2014] [Accepted: 05/10/2014] [Indexed: 06/03/2023]
Abstract
Euplotes crassus, a single-celled eukaryote, is directly affected by environmental contaminants. Here, exponentially cultured E. crassus were exposed to cadmium, copper, lead, and zinc and then the reactive oxygen species (ROS) and total glutathione (GSH) levels were measured. Subsequently, the transcriptional modulation of glutathione peroxidase (GPx) and glutathione reductase (GR) were estimated by quantitative RT-PCR. After an 8-h exposure, significantly higher increases in the relative ROS and total GSH levels were observed in exposed group, compared to the controls. Real-time PCR data revealed that the expression levels of GPx and GR mRNA were sensitively modulated within 8h of exposure to all heavy metals. These findings suggest that these genes may be involved in cellular defense mechanisms by modulating their gene expression against heavy metal-induced oxidative stress. Thus, they may be useful as potential molecular biomarkers to assess sediment environments for contaminants.
Collapse
Affiliation(s)
- Se-Hun Kim
- Department of Life Science, College of Natural Science, Sangmyung University, Seoul 110-743, South Korea
| | - Se-Joo Kim
- Deep-sea and Seabed Resources Research Division, Korea Institute of Ocean Science and Technology (KIOST), Ansan 426-744, South Korea
| | - Jae-Seong Lee
- Department of Biological Sciences, College of Science, Sungkyunkwan University, Suwon 440-746, South Korea
| | - Young-Mi Lee
- Department of Life Science, College of Natural Science, Sangmyung University, Seoul 110-743, South Korea.
| |
Collapse
|
19
|
Li J, Zhou L, Lin X, Yi Z, Al-Rasheid KAS. Characterizing dose-responses of catalase to nitrofurazone exposure in model ciliated protozoan Euplotes vannus for ecotoxicity assessment: enzyme activity and mRNA expression. Ecotoxicol Environ Saf 2014; 100:294-302. [PMID: 24075098 DOI: 10.1016/j.ecoenv.2013.08.021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2013] [Revised: 08/21/2013] [Accepted: 08/24/2013] [Indexed: 06/02/2023]
Abstract
In environmental studies, some biological responses, known as biomarkers, have been used as a powerful bioassay tool for more than four decades. Disparity between enzyme activity and mRNA abundance leads to correlation equivocality, which makes the application of biomarkers for environmental risk assessment more complicated. This study investigates this disparity in the case of catalase when used as a biomarker for detecting ecotoxicity induced by antibiotics in aquatic ecosystems. In particular, dose-responses for catalase activity and mRNA expression abundance were investigated in Euplotes vannus which were exposed to graded doses of nitrofurazone for several discrete durations, and dose-response models were developed to characterize the dose-response dynamics. Significant differences were found in both catalase activity and mRNA expression abundance among the E. vannus treated with nitrofurazone. Catalase activity showed a hormetic-like effect in terms of dose-response, characterized by a biphasic relationship which was more clearly evident after a longer exposure period, while mRNA expression abundance increased linearly with the exposure duration. Additionally, the correlation between catalase activity and mRNA expression abundance reversed along with the duration of exposure to nitrofurazone. Taken together, our results demonstrate that catalase mRNA expression offers a more straightforward dose-response model than enzyme activity. Our findings suggest that both catalase enzyme activity and mRNA expression abundance can be used jointly as bioassay tools for detecting ecotoxicity induced by nitrofurazone in aquatic ecosystems.
Collapse
Affiliation(s)
- Jiqiu Li
- Guangdong Provincial Key Laboratory for Healthy and Safe Aquaculture, College of Life Science, South China Normal University, Guangzhou 510631, Guangdong, China.
| | - Liang Zhou
- Guangdong Provincial Key Laboratory for Healthy and Safe Aquaculture, College of Life Science, South China Normal University, Guangzhou 510631, Guangdong, China
| | - Xiaofeng Lin
- Guangdong Provincial Key Laboratory for Healthy and Safe Aquaculture, College of Life Science, South China Normal University, Guangzhou 510631, Guangdong, China
| | - Zhenzhen Yi
- Guangdong Provincial Key Laboratory for Healthy and Safe Aquaculture, College of Life Science, South China Normal University, Guangzhou 510631, Guangdong, China
| | | |
Collapse
|
20
|
Candelori A, Luporini P, Alimenti C, Vallesi A. Characterization and expression of the gene encoding En-MAPK1, an intestinal cell kinase (ICK)-like kinase activated by the autocrine pheromone-signaling loop in the Polar Ciliate, Euplotes nobilii. Int J Mol Sci 2013; 14:7457-67. [PMID: 23552830 PMCID: PMC3645696 DOI: 10.3390/ijms14047457] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2013] [Revised: 03/21/2013] [Accepted: 03/21/2013] [Indexed: 11/16/2022] Open
Abstract
In the protozoan ciliate Euplotes, a transduction pathway resulting in a mitogenic cell growth response is activated by autocrine receptor binding of cell type-specific, water-borne signaling protein pheromones. In Euplotes raikovi, a marine species of temperate waters, this transduction pathway was previously shown to involve the phosphorylation of a nuclear protein kinase structurally similar to the intestinal-cell and male germ cell-associated kinases described in mammals. In E. nobilii, which is phylogenetically closely related to E. raikovi but inhabits Antarctic and Arctic waters, we have now characterized a gene encoding a structurally homologous kinase. The expression of this gene requires +1 translational frameshifting and a process of intron splicing for the production of the active protein, designated En-MAPK1, which contains amino acid substitutions of potential significance for cold-adaptation.
Collapse
Affiliation(s)
- Annalisa Candelori
- Laboratory of Eukaryotic Microbiology and Animal Biology, Department of Environmental and Natural Sciences, University of Camerino, Camerino 62032, Italy.
| | | | | | | |
Collapse
|
21
|
Dobri N, Oumarou EEN, Alimenti C, Ortenzi C, Luporini P, Vallesi A. Methionine sulfoxide reduction in ciliates: characterization of the ready-to-use methionine sulfoxide-R-reductase genes in Euplotes. Gene 2013. [PMID: 23206970 DOI: 10.1016/j.gene.2012.11.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Genes encoding the enzyme methionine sulfoxide reductase type B, specific to the reduction of the oxidized methionine-R form, were characterized from the expressed (macronuclear) genome of two ecologically separate marine species of Euplotes, i.e. temperate water E. raikovi and polar water E. nobilii. Both species were found to contain a single msrB gene with a very simple structural organization encoding a protein of 127 (E. raikovi) or 126 (E. nobilii) amino acid residues that belongs to the group of zinc-containing enzymes. Both msrB genes are constitutively expressed, suggesting that the MsrB enzyme plays an essential role in repairing oxidative damages that appear to be primarily caused by physiological cell aging in E. raikovi and by interactions with an O(2) saturated environment in E. nobilii.
Collapse
Affiliation(s)
- Nicoleta Dobri
- Dipartimento di Scienze Ambientali e Naturali, University of Camerino, 62032 Camerino (MC), Italy
| | | | | | | | | | | |
Collapse
|
22
|
Chen J, Yang BS, Liang AH. Domain motions of class I release factor induced by binding with class II release factor from Euplotes octocarinatus. Biochemistry (Mosc) 2012; 77:896-900. [PMID: 22860911 DOI: 10.1134/s000629791208010x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The binding of both factors (eRF1 and eRF3) is essential for fast kinetics of the termination of protein translation. The C-terminal domain of eRF1 is known to interact with the C domain of eRF3. Eo-eRF1b contains two highly conserved tryptophan residues (W-11 and W-373), W-11 located in the Eo-eRF1b N domain and W-373 located in the Eo-eRF1b C domain. Fluorimetry was used to study the interactions of the proteins. When binding with Eo-eRF3Cm6, the emission peak of Eo-eRF1b is blue shifted, while the emission peak of Eo-eRF1bC has no notable change. Our results suggest that the eRF1-eRF3 interaction induces the N and C domain of eRF1b to become closer to each other.
Collapse
Affiliation(s)
- Jie Chen
- Institute of Biotechnology and Institute of Molecular Science, Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Shanxi University, Taiyuan 030006, China
| | | | | |
Collapse
|
23
|
Zhou L, Li J, Lin X, Al-Rasheid KAS. Use of RAPD to detect DNA damage induced by nitrofurazone in marine ciliate, Euplotes vannus (Protozoa, Ciliophora). Aquat Toxicol 2011; 103:225-232. [PMID: 21481819 DOI: 10.1016/j.aquatox.2011.03.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2010] [Revised: 03/02/2011] [Accepted: 03/07/2011] [Indexed: 05/30/2023]
Abstract
The random amplified polymorphic DNA (RAPD) assay was evaluated as a potential tool to detect the ecotoxicity induced by nitrofurazone in marine ciliate, Euplotes vannus. The data revealed a reduction in viability of the test ciliates with increasing nitrofurazone concentration in the range of 0-24 mgl(-1) and time of exposure from 24 to 96 h. The nitrofurazone treated ciliates were subjected to DNA damage analysis by RAPD assay. Among the 33 test RAPD primers used in this study, 11 primers with 60-70% GC content produced unique polymorphic band patterns. A total of 213 bands of 155-3317 bp in molecular size range were observed in the untreated cells. In comparison with the control ciliates, the nitrofurazone treated groups showed differences in RAPD profiles with respect to the band intensity, disappearance of bands and appearance of new bands of amplified DNA. The variation of RAPD profiles showed both the time- and concentration-dependent relationships. The data suggested significant genomic template instability, which corresponds well with the viability of the test ciliates. Thus the results demonstrated the potential of the RAPD assay for application as a powerful tool for detecting genotoxicity induced by fishy drugs in aquatic environment.
Collapse
Affiliation(s)
- Liang Zhou
- Laboratory of Protozoology, Key Laboratory of Ecology and Environmental Science in Guangdong Higher Education, Guangdong Provincial Key Laboratory for Healthy and Safe Aquaculture, College of Life Science, South China Normal University, Guangzhou 510631, Guangdong, China
| | | | | | | |
Collapse
|
24
|
Chai B, Hao Y, Li C, Shen Q, Liang A. [Construction of cDNA library of protozoan ciliates Euplotes octocarinatus]. Wei Sheng Wu Xue Bao 2010; 50:316-321. [PMID: 20499635] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
UNLABELLED The protein biosynthesis in cells is an open process cooperatively regulated by many protein factors and enzymes, which form a complicated protein network and signal transduction pathway for mRNA metabolism and protein translation. OBJECTIVE To provide a platform for studying on the function of proteins involving in process of translation termination and the relationship among these proteins in ciliates. METHODS We constructed the cDNA library of protozoan ciliates Euplotes octocarinatus strictly following the procedure of BD Matchmaker Library Construction & Screening kit from Clontech. RESULTS We obtained a cDNA library of ciliates Euplotes, the titer of which was about 2.437 x 10(7) cfu/mL, which could suffice for functional gene screen. By using the class II polypeptide release factor (eRF3) as bait protein, we obtained some putative genes, including a partial cDNA putatively encoding RNA helicase. CONCLUSION This library will provide a convenient platform for identifying the functional genes in ciliates.
Collapse
Affiliation(s)
- Baofeng Chai
- Key Laboratory of Chemical Biology and Molecular Engineering of The Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China.
| | | | | | | | | |
Collapse
|
25
|
Vallabhaneni H, Fan-Minogue H, Bedwell DM, Farabaugh PJ. Connection between stop codon reassignment and frequent use of shifty stop frameshifting. RNA 2009; 15:889-897. [PMID: 19329535 PMCID: PMC2673066 DOI: 10.1261/rna.1508109] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2008] [Accepted: 02/05/2009] [Indexed: 05/27/2023]
Abstract
Ciliated protozoa of the genus Euplotes have undergone genetic code reassignment, redefining the termination codon UGA to encode cysteine. In addition, Euplotes spp. genes very frequently employ shifty stop frameshifting. Both of these phenomena involve noncanonical events at a termination codon, suggesting they might have a common cause. We recently demonstrated that Euplotes octocarinatus peptide release factor eRF1 ignores UGA termination codons while continuing to recognize UAA and UAG. Here we show that both the Tetrahymena thermophila and E. octocarinatus eRF1 factors allow efficient frameshifting at all three termination codons, suggesting that UGA redefinition also impaired UAA/UAG recognition. Mutations of the Euplotes factor restoring a phylogenetically conserved motif in eRF1 (TASNIKS) reduced programmed frameshifting at all three termination codons. Mutation of another conserved residue, Cys124, strongly reduces frameshifting at UGA while actually increasing frameshifting at UAA/UAG. We will discuss these results in light of recent biochemical characterization of these mutations.
Collapse
Affiliation(s)
- Haritha Vallabhaneni
- Program in Molecular and Cell Biology, Department of Biological Sciences, University of Maryland Baltimore County, Baltimore,Maryland 21250, USA
| | | | | | | |
Collapse
|
26
|
Xu J, Wang W, Chai BF, Liang AH. [Cloning and characterization of a novel trinucleotide repeat-containing gene GARP from Euplotes octocarinatus]. Yi Chuan 2009; 29:87-91. [PMID: 17284430 DOI: 10.1360/yc-007-0087] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The expansion of trinucleotide repeats in genome is related to the phthogenesis of several neurodegenerative diseases. A GARP (glutamic acid-rich protein) gene was isolated from the macronuclear plasmid mini library of Euplotes octocarinatus. A micronuclear version of the GARP gene was amplified by polymerase chain reaction. The macronuclear DNA molecule carrying the GARP gene is 460 bp long and shows the characteristics of macronuclear chromosomes of hypotrichous ciliates. One of the three cysteines is encoded by the opal codon TGA(88-90). The predicted open reading frame encodes a 112-amino acid polypeptide, with a predicted molecular mass of 13 kDa and an isoelectric point of 3.82. Micronuclear version of the GARP gene contains two internal eliminated sequences (IES), IES1 and IES2. IES1 is 41 bp long and is flanked by 5'-GA-3' direct repeats. IES2 is 41 bp long and flanked by 5'-TA-3' direct repeats. Transcriptional activity of GARP gene was confirmed by reverse transcription polymerase chain reaction (RT-PCR).
Collapse
Affiliation(s)
- Jing Xu
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan, China.
| | | | | | | |
Collapse
|
27
|
Li JJ, Nie Y, Liaing AH, Dang XH, Wang W. [EoRab43 regulating vesicular transport around the macronucleus in Euplotes octocarinatus]. Fen Zi Xi Bao Sheng Wu Xue Bao 2009; 42:35-42. [PMID: 19306687] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Rab family proteins play a crucial role in regulating vesicular traffic in eukaryotic cells. EoRab43 is an atypical Rab gene identified in Euplotes octocarinatus. In order to understand the function of EoRab43, the 153bp fragment of the 3'-end of EoRab43 gene was subcloned into expression vector pGEX-6P-1, and the recombinant plasmid pGEX-EoRab43(153bp) was transfered into E.coli BL21 (DE3) to express the fusion protein. The fusion protein GST-EoRab43C was expressed and purified by affinity chromatography. BALB/c mice were immunolized by purified GST-EoRab43C. The titer of anti-EoRab43C polyclonal antibody was detected by indirect ELISA assay and the specificity of the antibody was detected by Western blot. Immunofluorescence experiments were performed using anti-EoRab43C antibody in the cells of Euplotes. The results showed that EoRab43 displayed a punctuate pattern in the cytoplasm around the macronuclear chromosome of Euplotes.
Collapse
Affiliation(s)
- Jiang Jiao Li
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China
| | | | | | | | | |
Collapse
|
28
|
Turanov AA, Lobanov AV, Fomenko DE, Morrison HG, Sogin ML, Klobutcher LA, Hatfield DL, Gladyshev VN. Genetic code supports targeted insertion of two amino acids by one codon. Science 2009; 323:259-61. [PMID: 19131629 PMCID: PMC3088105 DOI: 10.1126/science.1164748] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Strict one-to-one correspondence between codons and amino acids is thought to be an essential feature of the genetic code. However, we report that one codon can code for two different amino acids with the choice of the inserted amino acid determined by a specific 3' untranslated region structure and location of the dual-function codon within the messenger RNA (mRNA). We found that the codon UGA specifies insertion of selenocysteine and cysteine in the ciliate Euplotes crassus, that the dual use of this codon can occur even within the same gene, and that the structural arrangements of Euplotes mRNA preserve location-dependent dual function of UGA when expressed in mammalian cells. Thus, the genetic code supports the use of one codon to code for multiple amino acids.
Collapse
MESH Headings
- 3' Untranslated Regions
- Amino Acid Sequence
- Animals
- Base Sequence
- Cell Line
- Codon/genetics
- Codon, Terminator/genetics
- Cysteine/genetics
- Cysteine/metabolism
- Euplotes/chemistry
- Euplotes/genetics
- Genetic Code
- Humans
- Molecular Sequence Data
- Mutation
- Protozoan Proteins/biosynthesis
- Protozoan Proteins/chemistry
- Protozoan Proteins/genetics
- RNA, Protozoan/genetics
- RNA, Protozoan/metabolism
- RNA, Transfer, Amino Acid-Specific/chemistry
- RNA, Transfer, Amino Acid-Specific/genetics
- RNA, Transfer, Cys/chemistry
- RNA, Transfer, Cys/genetics
- Recombinant Fusion Proteins/metabolism
- Selenocysteine/genetics
- Selenocysteine/metabolism
- Selenoproteins/biosynthesis
- Selenoproteins/chemistry
- Selenoproteins/genetics
Collapse
Affiliation(s)
- Anton A. Turanov
- Department of Biochemistry and Redox Biology Center, University of Nebraska, Lincoln, NE 68588
| | - Alexey V. Lobanov
- Department of Biochemistry and Redox Biology Center, University of Nebraska, Lincoln, NE 68588
| | - Dmitri E. Fomenko
- Department of Biochemistry and Redox Biology Center, University of Nebraska, Lincoln, NE 68588
| | - Hilary G. Morrison
- Josephine Bay Paul Center, Marine Biological Laboratory, Woods Hole, MA 02543
| | - Mitchell L. Sogin
- Josephine Bay Paul Center, Marine Biological Laboratory, Woods Hole, MA 02543
| | - Lawrence A. Klobutcher
- Department of Molecular, Microbial and Structural Biology, University of Connecticut Health Center, Farmington, CT 06032
| | - Dolph L. Hatfield
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892 USA
| | - Vadim N. Gladyshev
- Department of Biochemistry and Redox Biology Center, University of Nebraska, Lincoln, NE 68588
| |
Collapse
|
29
|
Lekomtsev SA, Kolosov PM, Frolova LI, Bidou L, Rousset JP, Kiselev LL. [How translation termination factor eRF1 Euplotes does not recognise UGA stop codon]. Mol Biol (Mosk) 2007; 41:1014-1022. [PMID: 18318120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
In universal-code eukaryotes, a single class-1 translation termination factor eRF1 decodes all three stop codons, UAA, UAG, and UGA. In some ciliates with variant genetic codes one or two stop codons are used to encode amino acid(s) and are not recognized by eRF1. In Stylonychia, UAG and UAA codons are reassigned as glutamine codons, and in Euplotes, UGA is reassigned as cysteine codon. In omnipotent eRF1s, stop codon recognition is associated with the N-terminal domain of eRF1. Because variant-code ciliates most likely evolved from universal code ancestor(s), structural features should exist in ciliate eRF1s that restrict their stop codon recognition. To find out amino acid residues which confer UAR-only specificity to Euplotes aediculatus eRF1, eRFI chimeras were constructed by swapping eRF1 E. aediculatus N-terminal domain sequences with the matching ones from the human protein. In these chimeras the MC-domain was from human eRF1. Functional analysis of these chimeric eRFI highlighted the crucial role of the two regions (positions 38-50 and 123-145) in the N-terminal domain of E. aediculatus eRF1 that restrict E. aediculatus eRF1 specificity toward UAR codons. Possibly, restriction of eRF1 specificity to UAR codons might have been an early event occurring in independent instances in ciliate evolutionary history, possibly facilitating the reassignment of UGA to sense codons.
Collapse
|
30
|
Julian Schwarz MV, Zuendorf A, Stoeck T. Morphology, Ultrastructure, Molecular Phylogeny, and Autecology of Euplotes elegans Kahl, 1932 (Hypotrichida; Euplotidae) Isolated from the Anoxic Mariager Fjord, Denmark. J Eukaryot Microbiol 2007; 54:125-36. [PMID: 17403153 DOI: 10.1111/j.1550-7408.2007.00243.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The morphology, autecology, and molecular phylogeny of an euryhaline Euplotes isolate collected from the anoxic water column of the Mariager Fjord in Denmark were investigated. The isolate matches the original description of Euplotes elegans Kahl, 1932 very well. However, its dorsal silverline system is clearly distinct from the redescription of this species by Tuffrau. Thus, a neotypification is proposed for E. elegans Kahl, 1932. The oval-shaped cell has a mean size of 107 x 51 microm and is characterized by 9.4 dorsolateral kineties, seven prominent dorsal ridges, large elongated ampullae, which encircle the dorsal kinetids, 18 kinetids in the middorsal row, nine frontoventral cirri, five transversal cirri, and three caudal cirri (two right caudal cirri and one left marginal cirrus). The dorsal silverline system is of the double type with the narrow polygons located on the right side of the dorsal kinetids. The ecological tolerances of this species to pH, salinity, temperature, and oxygen match the ambient environmental conditions of the sampling site. Molecular phylogeny was studied using small subunit rRNA (SSU rRNA) gene sequences. The molecular data cluster E. elegans with Euplotes raikovi, a member of the Euplotopsis group. The data suggest that the E. elegans-E. raikovi clade represents an isolated and deep branch at the base of the Euplotes tree.
Collapse
Affiliation(s)
- M V Julian Schwarz
- TU Kaiserslautern, School of Biology, Erwin-Schroedinger-Strasse 14, D-67663 Kaiserslautern, Germany.
| | | | | |
Collapse
|
31
|
Song L, Chai BF, Wang W, Liang AH. Identification of translational release factor eRF1a binding sites on eRF3 in Euplotes octocarinatus. Res Microbiol 2006; 157:842-50. [PMID: 16963230 DOI: 10.1016/j.resmic.2006.07.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2006] [Revised: 07/24/2006] [Accepted: 07/25/2006] [Indexed: 11/19/2022]
Abstract
Translation termination in eukaryotes is mediated by two polypeptide chain-release factors, eRF1 and eRF3. eRF1 recognizes stop signals, while eRF3 is a ribosome-dependent and eRF1-dependent GTPase. eRF1 forms a stable complex with eRF3 in vivo and in vitro. In the present study, a variety of truncated forms of Euplotes octocarinatus eRF3 were created, and systematic analysis of the interaction between E. octocarinatus eRF1a and these eRF3 mutants was performed by employing both in vivo a yeast two-hybrid assay and in vitro a pull-down assay. The results demonstrated that a short portion of the C-terminal domain of eRF3 is sufficient for eRF1a binding in E. octocarinatus. Specifically, the eRF1a-binding sites on eRF3 are located at a region containing amino acid residues 640-723 in E. octocarinatus eRF3. Amino acid sequence analysis of eRF3 from E. octocarinatus, humans and yeast showed that the eRF1a binding domain on E. octocarinatus eRF3 was similar to that of yeast eRF3 but different from that of human eRF3.
Collapse
Affiliation(s)
- Li Song
- Institute of Biotechnology, Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Shanxi University, Taiyuan 030006, China
| | | | | | | |
Collapse
|
32
|
Li LY, Chai BF, Liang AH, Sun YH, Wang W. [Cloning and sequence analysis of a novel member of the rab gene family from Euplotes octocarinatus]. Yi Chuan 2006; 28:437-42. [PMID: 16606597] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Rab proteins belong to a subfamily of small GTP-binding proteins of the Ras superfamily, which play an important role in intracellular vesicular traffic. In this study, a rab gene was obtained from Euplotes octocarinatus by polymerase chain reaction (PCR) and RT-PCR. The rab gene from macronucleic DNA was 884 bp in length, including non-coding regions and telomeric sequences at both ends. The rab gene from micronuclear DNA (723 bp), lacking of internal eliminated sequences, was identical to rab gene from macronuclear DNA. RT-PCR showed that the opening reading frame of the rab gene was 663 bp long. The rab gene from macronuclear DNA contained an intron of 60 bp at the position from 153 bp to 212 bp of macronuclear DNA. The rab gene had two in-frame TGAs encoding for cysteine in Euplotes octocarinatus. The rab gene used TAG as stop codon, which was the first report in Euplotes octocarinatus. The result of BLAST in NCBI demonstrates that the Rab shares a homology of 49-52% at the amino acid level with Rab1 proteins from a number of other eukaryote, which suggesting that the Rab is a Rab1 homolog. The rab gene was therefore designated Eo-rab-1N (GenBank accession number: DQ105562). The evolution of Eo-rab-1N was analyzed using phylogenetic tree of amino acids sequences of Rab1 obtained from GenBank.
Collapse
Affiliation(s)
- Ling-Yan Li
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China.
| | | | | | | | | |
Collapse
|
33
|
Abstract
Programmed translational frameshifts have been identified in genes from a broad range of organisms, but typically only a very few genes in a given organism require a frameshift for expression. In contrast, a recent analysis of gene sequences available in GenBank from ciliates in the genus Euplotes indicated that >5% required one or more +1 translational frameshifts to produce their predicted protein products. However, this sample of genes was nonrandom, biased, and derived from multiple Euplotes species. To test whether there truly is an abundance of frameshift genes in Euplotes, and to more accurately assess their frequency, we sequenced a random sample of 25 cloned genes/macronuclear DNA molecules from Euplotes crassus. Three new candidate +1 frameshift genes were identified in the sample that encode a membrane occupation and recognition nexus (MORN) repeat protein, a C(2)H(2)-type zinc finger protein, and a Ser/Thr protein kinase. Reverse transcription-PCR analyses indicate that all three genes are expressed in vegetatively proliferating cells and that the mRNAs retain the requirement of a frameshift. Although the sample of sequenced genes is relatively small, the results indicate that the frequency of genes requiring frameshifts in E. crassus is between 3.7% and 31.7% (at a 95% confidence interval). The current and past data also indicate that frameshift sites are found predominantly in genes that likely encode nonabundant proteins in the cell.
Collapse
Affiliation(s)
- Lawrence A Klobutcher
- Department of Molecular, Microbial and Structural Biology, University of Connecticut Health Center, Farmington, CT 06032, USA.
| |
Collapse
|
34
|
Salas-Marco J, Fan-Minogue H, Kallmeyer AK, Klobutcher LA, Farabaugh PJ, Bedwell DM. Distinct paths to stop codon reassignment by the variant-code organisms Tetrahymena and Euplotes. Mol Cell Biol 2006; 26:438-47. [PMID: 16382136 PMCID: PMC1346903 DOI: 10.1128/mcb.26.2.438-447.2006] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The reassignment of stop codons is common among many ciliate species. For example, Tetrahymena species recognize only UGA as a stop codon, while Euplotes species recognize only UAA and UAG as stop codons. Recent studies have shown that domain 1 of the translation termination factor eRF1 mediates stop codon recognition. While it is commonly assumed that changes in domain 1 of ciliate eRF1s are responsible for altered stop codon recognition, this has never been demonstrated in vivo. To carry out such an analysis, we made hybrid proteins that contained eRF1 domain 1 from either Tetrahymena thermophila or Euplotes octocarinatus fused to eRF1 domains 2 and 3 from Saccharomyces cerevisiae. We found that the Tetrahymena hybrid eRF1 efficiently terminated at all three stop codons when expressed in yeast cells, indicating that domain 1 is not the sole determinant of stop codon recognition in Tetrahymena species. In contrast, the Euplotes hybrid facilitated efficient translation termination at UAA and UAG codons but not at the UGA codon. Together, these results indicate that while domain 1 facilitates stop codon recognition, other factors can influence this process. Our findings also indicate that these two ciliate species used distinct approaches to diverge from the universal genetic code.
Collapse
Affiliation(s)
- Joe Salas-Marco
- Department of Microbiology, BBRB 432/Box 8, 1530 Third Avenue South, The University of Alabama at Birmingham, Birmingham, Alabama 35294-2170, USA
| | | | | | | | | | | |
Collapse
|
35
|
Wang W, Zhi H, Chai B, Liang A. Cloning and sequence analysis of the micronuclear and macronuclear gene encoding Rab protein of Euplotes octocarinatus. Biosci Biotechnol Biochem 2005; 69:649-52. [PMID: 15785000 DOI: 10.1271/bbb.69.649] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The DNA in a micronucleus undergoes remarkable rearrangements when it develops into a macronucleus after cell mating in the hypotrichous ciliate. A Rab gene was isolated from the macronuclear plasmid mini-library of Euplotes octocarinatus. A micronuclear version of the Rab gene was amplified by polymerase chain reaction (PCR). The macronuclear DNA molecule carrying the Rab gene is 767 bp long and shows characteristics typical of macronuclear chromosomes of hypotrichous ciliates. Three of the five cysteines are encoded by the opal codon UGA. The deduced protein is a 207-amino acid (aa) with a molecular mass of 23 kDa. The protein shares 36% identity with Rab 1 protein of Plasmodium and yeast. Analysis of the sequences indicated that the micronuclear version of the Rab gene contains two internal eliminated sequences, internal eliminated sequence (IES)1 and IES2. IES1 is flanked by a pair of hepta-nucleotide 5'-AAATTTT-3' direct repeats, and IES2 is flanked by 5'-TA-3' direct repeats.
Collapse
Affiliation(s)
- Wei Wang
- Institute of Biotechnology, Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Shanxi University, Taiyuan, P.R. China
| | | | | | | |
Collapse
|
36
|
Zhi H, Wang W, Li L, Chai B, Sun Y, Liang A. Cloning and analysis of 16 Rab genes from macronuclear DNA of Euplotes octocarinatus. ACTA ACUST UNITED AC 2005; 16:260-5. [PMID: 16147885 DOI: 10.1080/10425170500087793] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Rab proteins belong to the largest family of the Ras superfamily of small GTPase that play an important role in intracellular vesicular traffic. So far, almost 60 members of Rab family have been identified in mammalian cells. To further study the diversity and function of Rab protein in evolution, unicellular protozoa ciliates, Euplotes octocarinatus, were used in this study, Rab genes were screened by PCR method from macronuclear DNA of E. octocarinatus. Sixteen Rab genes were obtained. They share 87.6-99.5% identities. Highly conserved GTP-binding domains were found. There are some hot regions that diverse sharply in these genes as well.
Collapse
Affiliation(s)
- Hui Zhi
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, People's Republic of China
| | | | | | | | | | | |
Collapse
|
37
|
Pucciarelli S, Marziale F, Di Giuseppe G, Barchetta S, Miceli C. Ribosomal cold-adaptation: characterization of the genes encoding the acidic ribosomal P0 and P2 proteins from the Antarctic ciliate Euplotes focardii. Gene 2005; 360:103-10. [PMID: 16143466 DOI: 10.1016/j.gene.2005.06.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2004] [Revised: 04/14/2005] [Accepted: 06/02/2005] [Indexed: 10/25/2022]
Abstract
Molecular adaptation at low temperature requires specificities represented mainly by modifications in the gene sequence and consequently in the protein primary structure. To characterize the molecular mechanisms responsible for ribosome cold-adaptation, we compared the ribosomal P0 and P2 genes from the Antarctic ciliate Euplotes focardii with homologous genes from mesophilic organisms, including the ciliates Tetrahymena thermophila and non cold-adapted Euplotes species. This analysis revealed the presence of non synonymous mutations unique to E. focardii. In the P0 protein the mutations produced amino acid substitutions that increased the molecular flexibility that may facilitate a conformational adjustment associated with the interaction with the GTPase center of the large subunit rRNA, and increased the hydrophobicity of the region involved in the interaction with P1/P2 heterodimer, probably to keep associated the ribosomal stalk in the cold. In the P2 protein the mutations produced amino acid substitutions that increased the N-terminus flexibility, which may facilitate interactions with P1 protein in the formation of the heterodimer, and reduced the mobility of the C-terminus, to stabilize the stalk during ribosomal activity. Finally, P proteins appeared to be valid markers for investigating the phylogenetic origin of early eukaryotes.
Collapse
Affiliation(s)
- Sandra Pucciarelli
- Dipartimento di Biologia Molecolare, Cellulare e Animale, University of Camerino, Via F Camerini 2, 62032 Camerino (MC), Italy
| | | | | | | | | |
Collapse
|
38
|
Sfeir AJ, Chai W, Shay JW, Wright WE. Telomere-end processing the terminal nucleotides of human chromosomes. Mol Cell 2005; 18:131-8. [PMID: 15808515 DOI: 10.1016/j.molcel.2005.02.035] [Citation(s) in RCA: 154] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2004] [Revised: 02/17/2005] [Accepted: 02/28/2005] [Indexed: 10/25/2022]
Abstract
Mammalian telomeres end in single-stranded, G-rich 3' overhangs resulting from both the "end-replication problem" (the inability of DNA polymerase to replicate the very end of the telomeres) and postreplication processing. Telomeric G-rich overhangs are precisely defined in ciliates; the length and the terminal nucleotides are fixed. Human telomeres have very long overhangs that are heterogeneous in size (35-600 nt), indicating that their processing must differ in some respects from model organisms. We developed telomere-end ligation protocols that allowed us to identify the terminal nucleotides of both the C-rich and the G-rich telomere strands. Up to approximately 80% of the C-rich strands terminate in CCAATC-5', suggesting that after replication a nuclease with high specificity or constrained action acts on the C strand. In contrast, the G-terminal nucleotide was less precise than Tetrahymena and Euplotes but still had a bias that changed as a function of telomerase expression.
Collapse
Affiliation(s)
- Agnel J Sfeir
- Department of Cell Biology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390, USA
| | | | | | | |
Collapse
|
39
|
Abstract
A number of recent studies indicate that programmed + 1 ribosomal frameshifting is frequently required for the expression of genes in species of the genus Euplotes. In E. crassus, three genes encoding the telomerase reverse transcriptase (TERT) subunit have been previously found to possess one or two + 1 frameshift sites. To examine the origin of frameshift sites within the Euplotes group, we have isolated segments of the TERT gene from five Euplotes species. Coupled with phylogenetic analysis, the results indicate that one frameshift site in the TERT gene arose late in the evolution of the group. In addition, a novel frameshift site was identified in the TERT gene of E. minuta, a species where frameshifting has not been previously reported. Coupled with other studies, the results indicate that frameshift sites have arisen during the diversification of the euplotids. The results also are discussed in regard to the mutations necessary to generate frameshift sites, and the specialization of TERT protein function that has apparently occurred in E. crassus.
Collapse
Affiliation(s)
- Matthias Möllenbeck
- Institute of Cell Biology, University Witten/Herdecke, Stockumer Str. 10, 58453 Witten, Germany.
| | | | | |
Collapse
|
40
|
Aigner S, Cech TR. The Euplotes telomerase subunit p43 stimulates enzymatic activity and processivity in vitro. RNA 2004; 10:1108-18. [PMID: 15208446 PMCID: PMC1370601 DOI: 10.1261/rna.7400704] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2004] [Accepted: 04/29/2004] [Indexed: 05/19/2023]
Abstract
Telomerase is a reverse transcriptase that synthesizes telomeric DNA repeats at the ends of eukaryotic chromosomes. Although it is minimally composed of a conserved catalytic protein subunit (TERT) and an RNA component, additional accessory factors present in the holoenzyme play crucial roles in the biogenesis and function of the enzyme complex. Telomerase from the ciliate Tetrahymena can be reconstituted in active form in vitro. Using this system, we show that p43, a telomerase-specific La-motif protein from the ciliate Euplotes, stimulates activity and increases repeat addition processivity of telomerase. Activity enhancement by p43 requires its incorporation into a TERT.RNA.p43 ternary complex but is independent of other dissociable protein factors functioning in telomerase complex assembly. Stimulation is enhanced at elevated temperatures, supporting a role for p43 in structural stabilization of a critical region of the RNA subunit. To our knowledge, this represents the first demonstration that an authentic telomerase accessory protein can directly affect the enzymatic activity of the core enzyme in vitro.
Collapse
Affiliation(s)
- Stefan Aigner
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309-0215, USA
| | | |
Collapse
|
41
|
Chai BF, Song L, Fu YJ, Wang W, Liang AH. Interaction of two classes of release factors from Euplotes octocarinatus. Yi Chuan Xue Bao 2004; 31:460-7. [PMID: 15478605] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 04/30/2023]
Abstract
Translation termination on the ribosome is an essential process for cell viability. This process is maintained by two classes of peptide release factors (RF1/RF2, RF3 and eRF1, eRF3 in prokaryotes and eukaryotes, respectively). In protozoa ciliates Euplotes octocarinatus, an unicellular eukaryotes, universal stop codon UGA is reassigned for cysteine suggesting the specificity of evolution of translation termination system. We cloned two classes of release factors from Euplotes octocarinatus previously. In this paper, three in-frame stop codons UGA in Eo-eRF3 gene were mutated mediated by PCR site directed mutagenesis method. The interaction between eRF1 and eRF3 from E. octocarinatus was assayed in vivo using Yeast Two-hybrid System, which has an advantage of highly sensitivity. The results showed that the eRF1 x eRF3 complex was formed in living cells to function in the process of translation termination, differing from that in prokaryotes in which RF1/RF2 and RF3 function separately. The evolution of translation termination of life-form was analyzed using phylogenetic tree of amino acids sequences of RFs (32 (e) RF1s and 24 (e) RF3s) obtained from GenBank. Two classes of RFs are useful information in analysis of evolution of life-form and further elucidation of mechanism of translation termination of protein synthesis on ribosome.
Collapse
Affiliation(s)
- Bao-Feng Chai
- Key Laboratory of Chemical Biology and Molecular Engineering of Education Ministry, Shanxi University, Taiyuan 030006, China.
| | | | | | | | | |
Collapse
|
42
|
Khlebovich VV, Degtyarev AV. Mechanism of defensive morph formation in Euplites aediculatus (Ciliate, Hypotrichida). Dokl Biol Sci 2003; 392:445-6. [PMID: 14650882 DOI: 10.1023/a:1026196309596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- V V Khlebovich
- Zoological Institute, Russian Academy of Sciences, Universitetskaya nab. 1, St. Petersburg, 199034 Russia
| | | |
Collapse
|
43
|
Abstract
Telomerase-mediated healing of broken chromosomes gives rise to terminal deletions and is repressed in most organisms. In ciliated protozoa, however, chromosome fragmentation and de novo telomere addition are part of the developmental program. Work by in this issue of Cell indicates that in Euplotes crassus, this is mediated through switching between different telomerase reverse transcriptase isoforms.
Collapse
Affiliation(s)
- Gaël Cristofari
- Swiss Institute for Experimental Cancer Research (ISREC), CH-1066 Epalinges, Switzerland
| | | |
Collapse
|
44
|
Karamysheva Z, Wang L, Shrode T, Bednenko J, Hurley LA, Shippen DE. Developmentally programmed gene elimination in Euplotes crassus facilitates a switch in the telomerase catalytic subunit. Cell 2003; 113:565-76. [PMID: 12787498 DOI: 10.1016/s0092-8674(03)00363-5] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The primary function of telomerase is to maintain preexisting telomere tracts. In the ciliate Euplotes crassus, however, telomerase RNP structure and substrate recognition are altered during macronuclear development to facilitate de novo telomere addition. We found that E. crassus harbors three TERT genes encoding the telomerase catalytic subunit that not only vary in their nucleotide and predicted protein sequences, but also in their expression profiles. Expression of EcTERT-1 and -3 correlates with the requirement for telomere maintenance, while that of EcTERT-2 correlates with de novo telomere synthesis. All three genes appear to require ribosomal frameshifting for expression of catalytically active protein. The transcriptionally active form of EcTERT-2 exists only transiently in mated cells and is absent from the vegetative macronucleus. Thus, telomerase expression in Euplotes is controlled by unique regulatory mechanisms that culminate in a developmental switch to a different catalytic subunit with properties suited to de novo telomere addition.
Collapse
Affiliation(s)
- Zemfira Karamysheva
- Department of Biochemistry and Biophysics, Texas A&M University, 2128 TAMU, College Station, TX 77843, USA
| | | | | | | | | | | |
Collapse
|
45
|
Abstract
Telomerase is a specialized reverse transcriptase synthesizing DNA repeats at telomeres. In addition to the RNA and catalytic protein components, telomerase from the ciliate Euplotes aediculatus contains the subunit p43. This protein is homologous to the La autoantigen, functioning in maturation of RNA polymerase III transcripts. Here we provide evidence that p43 is primarily associated with the telomerase ribonucleoprotein in vivo. Recombinant p43 binds telomerase RNA with low-nanomolar affinity in vitro, recognizing stem I and adjacent nucleotides or structures in the core of the RNA. Unlike authentic La proteins, p43 does not bind strongly to RNA polymerase III precursor transcripts and does not exhibit a marked binding preference for 3'-terminal oligouridylate residues. In isolated macronuclei, p43 largely colocalizes with telomerase RNA in discrete foci. These findings suggest that p43 is not the Euplotes La protein but instead plays a dedicated role in telomerase assembly and/or function. Thus, p43 joins the telomerase reverse transcriptase and the yeast proteins Est1p and Est3p as the only telomerase-specific proteins identified so far.
Collapse
Affiliation(s)
- Stefan Aigner
- Department of Chemistry and Biochemistry and Howard Hughes Medical Institute, University of Colorado, Boulder, Colorado 80309-0215, USA
| | | | | | | |
Collapse
|
46
|
Möllenbeck M, Postberg J, Paeschke K, Rossbach M, Jönsson F, Lipps HJ. The telomerase-associated protein p43 is involved in anchoring telomerase in the nucleus. J Cell Sci 2003; 116:1757-61. [PMID: 12665556 DOI: 10.1242/jcs.00351] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Telomere replication of eukaryotic chromosomes is achieved by a specialized enzyme, the telomerase. Although the biochemistry of end-replication is well understood, little is known about the organization of the end-replication machinery, its regulation throughout the cell cycle or the biological function of the telomerase-associated proteins. Here we investigate the function of the telomerase-associated protein p43 within the macronucleus of the ciliated protozoa Euplotes. It has been shown that p43 binds in vitro to the RNA subunit of telomerase and shares homology with the La autoantigen family. It therefore has been suggested that it is involved in the assembly and/or nuclear retention of telomerase. We show that the p43-telomerase complex is bound to a subnuclear structure in vivo and is resistant to electroelution. Upon inhibition of p43 or telomerase expression by RNAi, which in this study was used for the first time in spirotrichs, this complex is no longer retained in the nucleus. Further analysis revealed that the p43-telomerase complex is bound to the nuclear matrix in vivo and that after inhibition of p43 expression, telomerase is released from this structure, strongly suggesting that p43 is involved in anchoring of telomerase in the nucleus. This is the first in vivo demonstration of the biological function of this telomerase-associated component involved in telomere replication and allows us to propose a model for the organization of the end-replication machinery in the eukaryotic cell.
Collapse
Affiliation(s)
- Matthias Möllenbeck
- Institute of Cell Biology, University Witten/Herdecke, Stockumer Strasse 10, D-58453 Witten, Germany
| | | | | | | | | | | |
Collapse
|
47
|
Sharp SI, Pickrell JK, Jahn CL. Identification of a novel "chromosome scaffold" protein that associates with Tec elements undergoing en masse elimination in Euplotes crassus. Mol Biol Cell 2003; 14:571-84. [PMID: 12589055 PMCID: PMC149993 DOI: 10.1091/mbc.e02-08-0542] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
During macronuclear development in the ciliate Euplotes crassus, the highly repetitive, transposon-like Tec elements possess an unusual chromatin structure. We observed that the Tec element chromatin is highly resistant to salt extraction and behaves like a nuclear matrix/chromosome scaffold-associated structure. Standard matrix/scaffold extraction procedures identified two major proteins: 1) an ~140-kDa protein that seems to be topoisomerase II based on its reactivity with anti-topoisomerase II antibodies, and 2) an 85-kDa protein that we further purified by acid extraction and have shown to be a novel protein by sequence analysis of its gene. The 85-kDa protein (p85) is a developmental stage-specific protein and is located exclusively in the developing macronucleus. Immunolocalization studies of p85 show that it colocalizes with topoisomerase II in chromatin. In addition, in situ hybridization combined with immunofluorescence localization of the proteins indicates that 100% of the Tec elements colocalize with 70% of the p85, whereas no significant colocalization with a total macronuclear sequence-specific probe is observed. p85 is the first developmental stage-specific protein identified as being specifically associated with sequences undergoing elimination in E. crassus.
Collapse
Affiliation(s)
- Suzanne I Sharp
- Department of Cell and Molecular Biology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois 60611-3008, USA
| | | | | |
Collapse
|
48
|
Petroni G, Rosati G, Vannini C, Modeo L, Dini F, Verni F. In situ identification by fluorescently labeled oligonucleotide probes of morphologically similar, closely related ciliate species. Microb Ecol 2003; 45:156-162. [PMID: 12491024 DOI: 10.1007/s00248-002-2016-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Ciliate protozoa are important members of microbial communities in which they play specific ecological roles. The determination of single species distribution is fundamental for food web analysis, but species recognition, which is mainly based on morphological characters, is often difficult between closely related species. The use of species-specific, purposely designed, fluorescently labeled probes for in situ hybridization is here presented as an easy and fast identification method for three closely related species belonging to the widespread genus Euplotes, namely E. crassus, E. vannus, and E. minuta, that in spite of their remarkable morphological similarity have significant metabolic and ecological differences. These three species can be detected simultaneously, provided the probes employed are bound to different fluorescent dyes: in this way their relative abundance and their population dynamics in the natural environment can be evaluated. As more ciliate sequences become available in databases, species-specific probes can be designed for other ciliates, thus rendering the application of the method of more general importance. The probes used in this study may also provide a tool to prevent erroneous species identification in future studies.
Collapse
Affiliation(s)
- G Petroni
- Dipartmento di Etologia, Ecologia, Evoluzione, Università di Pisa, Pisa, Italy
| | | | | | | | | | | |
Collapse
|
49
|
Doak TG, Witherspoon DJ, Jahn CL, Herrick G. Selection on the genes of Euplotes crassus Tec1 and Tec2 transposons: evolutionary appearance of a programmed frameshift in a Tec2 gene encoding a tyrosine family site-specific recombinase. Eukaryot Cell 2003; 2:95-102. [PMID: 12582126 PMCID: PMC141166 DOI: 10.1128/ec.2.1.95-102.2003] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The Tec1 and Tec2 transposons of the ciliate Euplotes crassus carry a gene for a tyrosine-type site-specific recombinase. The expression of the Tec2 gene apparently uses a programmed +1 frameshift. To test this hypothesis, we first examined whether this gene has evolved under purifying selection in Tec1 and Tec2. Each element carries three genes, and each has evolved under purifying selection for the function of its encoded protein, as evidenced by a dearth of nonsynonymous changes. This distortion of divergence is apparent in codons both 5' and 3' of the frameshift site. Thus, Tec2 transposons have diverged from each other while using a programmed +1 frameshift to produce recombinase, the function of which is under purifying selection. What might this function be? Tyrosine-type site-specific recombinases are extremely rare in eukaryotes, and Tec elements are the first known eukaryotic type II transposons to encode a site-specific recombinase. Tec elements also encode a widespread transposase. The Tec recombinase might function in transposition, resolve products of transposition (bacterial replicative transposons use recombinase or resolvase to separate joined replicons), or provide a function that benefits the ciliate host. Transposons in ciliated protozoa are removed from the macronucleus, and it has been proposed that the transposons provide this "excisase" activity.
Collapse
Affiliation(s)
- Thomas G Doak
- Department of Pathology, School of Medicine, University of Utah, Salt Lake City, Utah 84132, USA
| | | | | | | |
Collapse
|
50
|
Jacobs ME, Sánchez-Blanco A, Katz LA, Klobutcher LA. Tec3, a new developmentally eliminated DNA element in Euplotes crassus. Eukaryot Cell 2003; 2:103-14. [PMID: 12582127 PMCID: PMC141165 DOI: 10.1128/ec.2.1.103-114.2003] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2002] [Accepted: 09/23/2002] [Indexed: 11/20/2022]
Abstract
More than 100,000 interstitial segments of DNA (internal eliminated sequences [IESs]) are excised from the genome during the formation of a new macronucleus in Euplotes crassus. IESs include unique sequence DNA as well as two related families of transposable elements, Tec1 and Tec2. Here we describe a new class of E. crassus transposons, Tec3, which is present in 20 to 30 copies in the micronuclear genome. Tec3 elements have long inverted terminal repeats and contain a degenerate open reading frame encoding a tyrosine-type recombinase. One characterized copy of Tec3 (Tec3-1) is 4.48 kbp long, has 1.23-kbp inverted terminal repeats, and resides within the micronuclear copy of the ribosomal protein L29 gene (RPL29). The 23 bp at the extreme ends of this element are very similar to those in other E. crassus IESs and, like these other IESs, Tec3-1 is excised during the polytene chromosome stage of macronuclear development to generate a free circular form with an unusual junction structure. In contrast, a second cloned element, Tec3-2, is quite similar to Tec3-1 but lacks the terminal 258 bp of the inverted repeats, so that its ends do not resemble the other E. crassus IES termini. The Tec3-2 element appears to reside in a large segment of the micronuclear genome that is subject to developmental elimination. Models for the origins of these two types of Tec3 elements are presented, along with a discussion of how some members of this new transposon family may have come to be excised by the same machinery that removes other E. crassus IESs.
Collapse
Affiliation(s)
- Mary Ellen Jacobs
- Department of Biochemistry, University of Connecticut Health Center, Farmington, Connecticut 06030, USA.
| | | | | | | |
Collapse
|