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https://www.readbyqxmd.com/read/28509379/microbial-eukaryotes-that-lack-sterols
#1
Kiyotaka Takishita, Yoshito Chikaraishi, Goro Tanifuji, Naohiko Ohkouchi, Tetsuo Hashimoto, Katsunori Fujikura, Andrew J Roger
It is widely held that sterols are key cyclic triterpenoid lipids in eukaryotic cell membranes and are synthesized through oxygen-dependent multi-enzyme pathways. However, there are known exceptions-ciliated protozoans, such as Tetrahymena, along with diverse low-oxygen adapted eukaryotes produce, instead of sterols, the cyclic triterpenoid lipid tetrahymanol that does not require molecular oxygen for its biosynthesis. Here, we report that a number of anaerobic microbial eukaryotes (protists) utilize neither sterols nor tetrahymanol in their membranes...
May 16, 2017: Journal of Eukaryotic Microbiology
https://www.readbyqxmd.com/read/28467816/prediction-of-the-aquatic-toxicity-of-aromatic-compounds-to-tetrahymena-pyriformis-through-support-vector-regression
#2
Qiang Su, Wencong Lu, Dongshu Du, Fuxue Chen, Bing Niu, Kuo-Chen Chou
Toxicity evaluation is an extremely important process during drug development. It is usually initiated by experiments on animals, which is time-consuming and costly. To speed up such a process, a quantitative structure-activity relationship (QSAR) study was performed to develop a computational model for correlating the structures of 581 aromatic compounds with their aquatic toxicity to tetrahymena pyriformis. A set of 68 molecular descriptors derived solely from the structures of the aromatic compounds were calculated based on Gaussian 03, HyperChem 7...
April 13, 2017: Oncotarget
https://www.readbyqxmd.com/read/28413159/the-hippo-pathway-maintains-the-equatorial-division-plane-in-the-ciliate-tetrahymena
#3
Yu-Yang Jiang, Wolfgang Maier, Ralf Baumeister, Gregory Minevich, Ewa Joachimiak, Zheng Ruan, Natarajan Kannan, Diamond Clarke, Joseph Frankel, Jacek Gaertig
The mechanisms that govern pattern formation within the cell are poorly understood. Ciliates carry on their surface an elaborate pattern of cortical organelles that are arranged along the anteroposterior and circumferential axes by largely unknown mechanisms. Ciliates divide by tandem duplication: the cortex of the pre-division cell is remodeled into two similarly-sized and complete daughters. In the conditional cdaI-1 mutant of Tetrahymena thermophila, the division plane migrates from its initially correct equatorial position toward the cell's anterior, resulting in unequal cell division, and defects in nuclear divisions and cytokinesis...
April 16, 2017: Genetics
https://www.readbyqxmd.com/read/28402567/nonsense-mediated-mrna-decay-in-tetrahymena-is-ejc-independent-and-requires-a-protozoa-specific-nuclease
#4
Miao Tian, Wentao Yang, Jing Zhang, Huai Dang, Xingyi Lu, Chengjie Fu, Wei Miao
Nonsense-mediated mRNA decay (NMD) is essential for removing premature termination codon-containing transcripts from cells. Studying the NMD pathway in model organisms can help to elucidate the NMD mechanism in humans and improve our understanding of how this biologically important process has evolved. Ciliates are among the earliest branching eukaryotes; their NMD mechanism is poorly understood and may be primordial. We demonstrate that highly conserved Upf proteins (Upf1a, Upf2 and Upf3) are involved in the NMD pathway of the ciliate, Tetrahymena thermophila...
April 11, 2017: Nucleic Acids Research
https://www.readbyqxmd.com/read/28398483/function-of-nuclear-membrane-proteins-in-shaping-the-nuclear-envelope-integrity-during-closed-mitosis
#5
Hui-Ju Yang, Masaaki Iwamoto, Yasushi Hiraoka, Tokuko Haraguchi
The nuclear envelope (NE) not only protects the genome from being directly accessed by detrimental agents but also regulates genome organization. Breaches in NE integrity threaten genome stability and impede cellular function. Nonetheless, the NE constantly remodels, and NE integrity is endangered in dividing or differentiating cells. Specifically, in unicellular eukaryotes undergoing closed mitosis, the NE expands instead of breaking down during chromosome segregation. The newly assembling nuclear pore complexes (NPCs) penetrate the existing NE in interphase...
June 1, 2017: Journal of Biochemistry
https://www.readbyqxmd.com/read/28386019/compositionally-distinct-nuclear-pore-complexes-of-functionally-distinct-dimorphic-nuclei-in-ciliate-tetrahymena
#6
Masaaki Iwamoto, Hiroko Osakada, Chie Mori, Yasuhiro Fukuda, Koji Nagao, Chikashi Obuse, Yasushi Hiraoka, Tokuko Haraguchi
The nuclear pore complex (NPC), a gateway for nucleocytoplasmic trafficking, is composed of about 30 different proteins called nucleoporins. It remains unknown whether the NPCs within a species are homogeneous or vary depending on the cell type, or physiological condition. Here, we present evidence for compositionally distinct NPCs that form within a single cell in a binucleated ciliate. In Tetrahymena thermophila, each cell contains both a transcriptionally-active macronucleus (MAC) and a germline micronucleus (MIC)...
April 6, 2017: Journal of Cell Science
https://www.readbyqxmd.com/read/28381425/an-endosomal-syntaxin-and-the-ap-3-complex-are-required-for-formation-and-maturation-of-candidate-lysosome-related-secretory-organelles-mucocysts-in-tetrahymena-thermophila
#7
Harsimran Kaur, Daniela Sparvoli, Hiroko Osakada, Masaaki Iwamoto, Tokuko Haraguchi, Aaron P Turkewitz
The ciliate Tetrahymena thermophila synthesizes large secretory vesicles called mucocysts. Mucocyst biosynthesis shares features with dense core granules (DCGs) in animal cells, including proteolytic processing of cargo proteins during maturation. However, other molecular features have suggested relatedness to lysosome-related organelles (LROs). LROs, which include diverse organelles in animals, are formed via convergence of secretory and endocytic trafficking. Here we analyzed Tetrahymena Stx7l1p (syntaxin 7-like 1), a Qa SNARE whose homologs in other lineages are linked with vacuoles/LROs...
April 5, 2017: Molecular Biology of the Cell
https://www.readbyqxmd.com/read/28335309/separation-of-bacteria-protozoa-and-carbon-nanotubes-by-density-gradient-centrifugation
#8
Monika Mortimer, Elijah J Petersen, Bruce A Buchholz, Patricia A Holden
Sustainable production and use of carbon nanotube (CNT)-enabled materials require efficient assessment of CNT environmental hazards, including the potential for CNT bioaccumulation and biomagnification in environmental receptors. Microbes, as abundant organisms responsible for nutrient cycling in soil and water, are important ecological receptors for studying the effects of CNTs. Quantification of CNT association with microbial cells requires efficient separation of CNT-associated cells from individually dispersed CNTs and CNT agglomerates...
October 12, 2016: Nanomaterials
https://www.readbyqxmd.com/read/28334205/tetrahymena-phagocytic-vesicles-as-ecological-micro-niches-of-phage-transfer
#9
Iqbal Aijaz, Gerald B Koudelka
The microbial communities in natural environments such as soil, pond water, or animal rumens are composed of a diverse mixture of bacteria and protozoa including ciliates or flagellates. In such microbiomes, a major source of bacterial mortality is grazing by phagocytic protists. Many protists are omnivorous heterotrophs, feeding on a range of different bacterial species. Due to this indiscriminate feeding, different bacterial species can assemble together in the same phagocytic vesicles where they can potentially exchange genetic material...
April 1, 2017: FEMS Microbiology Ecology
https://www.readbyqxmd.com/read/28318795/mechanisms-of-toxic-action-of-silver-nanoparticles-in-the-protozoan-tetrahymena-thermophila-from-gene-expression-to-phenotypic-events
#10
Katre Juganson, Monika Mortimer, Angela Ivask, Sandra Pucciarelli, Cristina Miceli, Kaja Orupõld, Anne Kahru
Silver nanoparticles (AgNPs) are highly toxic to aquatic organisms, however, there is no consensus whether the toxicity is caused solely by released Ag-ions or also by reactive oxygen species (ROS). Here, the effects of protein-coated AgNPs (14.6 nm, Collargol) were studied on viability, oxidative stress and gene expression levels in wild type strains (CU427 and CU428) of ciliate Tetrahymena thermophila. Viability-based 24 h EC50 values of AgNPs were relatively high and significantly different for the two strains: ∼100 mg/L and ∼75 mg/L for CU427 and CU428, respectively...
March 16, 2017: Environmental Pollution
https://www.readbyqxmd.com/read/28301767/progress-in-human-and-tetrahymena-telomerase-structure
#11
Henry Chan, Yaqiang Wang, Juli Feigon
Telomerase is an RNA-protein complex that extends the 3' ends of linear chromosomes, using a unique telomerase reverse transcriptase (TERT) and template in the telomerase RNA (TR), thereby helping to maintain genome integrity. TR assembles with TERT and species-specific proteins, and telomerase function in vivo requires interaction with telomere-associated proteins. Over the past two decades, structures of domains of TR and TERT as well as other telomerase- and telomere-interacting proteins have provided insights into telomerase function...
March 15, 2017: Annual Review of Biophysics
https://www.readbyqxmd.com/read/28287229/stereochemical-investigations-of-the-tetrahymena-cyclase-a-model-system-for-euphane-tirucallane-biosynthesis
#12
José-Luis Giner, Ju Feng
The squalene cyclase of Tetrahymena pyriformis cyclizes 2,3-dihydrosqualene to euph-7-ene. This was used as a model for euphane biosynthesis. D-ring formation was demonstrated to involve pre-chair folding through an experiment with 2,3-dihydro-5-oxasqualene. This requires that a non-least motion rotation (120°) of the C17-20 bond in the intermediate deoxydammaranyl cation occurs before the first 1,2-hydride shift. Truncated substrates relieved the hindrance associated with this rotation and permitted a least motion pathway...
March 13, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28273462/negative-regulators-of-an-rnai-heterochromatin-positive-feedback-loop-safeguard-somatic-genome-integrity-in-tetrahymena
#13
Jan H Suhren, Tomoko Noto, Kensuke Kataoka, Shan Gao, Yifan Liu, Kazufumi Mochizuki
RNAi-mediated positive feedback loops are pivotal for the maintenance of heterochromatin, but how they are downregulated at heterochromatin-euchromatin borders is not well understood. In the ciliated protozoan Tetrahymena, heterochromatin is formed exclusively on the sequences that are removed from the somatic genome by programmed DNA elimination, and an RNAi-mediated feedback loop is important for assembling heterochromatin on the eliminated sequences. In this study, we show that the heterochromatin protein 1 (HP1)-like protein Coi6p, its interaction partners Coi7p and Lia5p, and the histone demethylase Jmj1p are crucial for confining the production of small RNAs and the formation of heterochromatin to the eliminated sequences...
March 7, 2017: Cell Reports
https://www.readbyqxmd.com/read/28238660/structure-function-studies-link-class-ii-viral-fusogens-with-the-ancestral-gamete-fusion-protein-hap2
#14
Jennifer Fricke Pinello, Alex L Lai, Jean K Millet, Donna Cassidy-Hanley, Jack H Freed, Theodore G Clark
The conserved transmembrane protein, HAP2/GCS1, has been linked to fertility in a wide range of taxa and is hypothesized to be an ancient gamete fusogen. Using template-based structural homology modeling, we now show that the ectodomain of HAP2 orthologs from Tetrahymena thermophila and other species adopt a protein fold remarkably similar to the dengue virus E glycoprotein and related class II viral fusogens. To test the functional significance of this predicted structure, we developed a flow-cytometry-based assay that measures cytosolic exchange across the conjugation junction to rapidly probe the effects of HAP2 mutations in the Tetrahymena system...
March 6, 2017: Current Biology: CB
https://www.readbyqxmd.com/read/28216593/biomethylation-and-volatilization-of-arsenic-by-model-protozoan-tetrahymena-pyriformis-under-different-phosphate-regimes
#15
Xixiang Yin, Lihong Wang, Zhanchao Zhang, Guolan Fan, Jianjun Liu, Kaizhen Sun, Guo-Xin Sun
Tetrahymena pyriformis, a freshwater protozoan, is common in aquatic systems. Arsenic detoxification through biotransformation by T. pyriformis is important but poorly understood. Arsenic metabolic pathways (including cellular accumulation, effluxion, biomethylation, and volatilization) of T. pyriformis were investigated at various phosphate concentrations. The total intracellular As concentration increased markedly as the external phosphate concentration decreased. The highest concentration was 168.8 mg·kg(-1) dry weight, after exposure to As(V) for 20 h...
February 14, 2017: International Journal of Environmental Research and Public Health
https://www.readbyqxmd.com/read/28212786/interplay-between-microbial-trait-dynamics-and-population-dynamics-revealed-by-the-combination-of-laboratory-experiment-and-computational-approaches
#16
Kenta Suzuki, Yuji Yamauchi, Takehito Yoshida
Filament formation is a common bacterial defense mechanism and possibly has a broad impact on microbial community dynamics. In order to examine the impact of filament formation on population dynamics, we developed an experimental system with a filamentous bacterium Flectobacillus sp. MWH38 and a ciliate predator Tetrahymena pyriformis. In this system, the effective defense of Flectobacillus resulted in the extinction of Tetrahymena by allowing almost no population growth. The result of a kairomone experiment suggested the existence of chemical signals for filament formation...
February 16, 2017: Journal of Theoretical Biology
https://www.readbyqxmd.com/read/28190732/the-macronuclear-genome-of-stentor-coeruleus-reveals-tiny-introns-in-a-giant-cell
#17
Mark M Slabodnick, J Graham Ruby, Sarah B Reiff, Estienne C Swart, Sager Gosai, Sudhakaran Prabakaran, Ewa Witkowska, Graham E Larue, Susan Fisher, Robert M Freeman, Jeremy Gunawardena, William Chu, Naomi A Stover, Brian D Gregory, Mariusz Nowacki, Joseph Derisi, Scott W Roy, Wallace F Marshall, Pranidhi Sood
The giant, single-celled organism Stentor coeruleus has a long history as a model system for studying pattern formation and regeneration in single cells. Stentor [1, 2] is a heterotrichous ciliate distantly related to familiar ciliate models, such as Tetrahymena or Paramecium. The primary distinguishing feature of Stentor is its incredible size: a single cell is 1 mm long. Early developmental biologists, including T.H. Morgan [3], were attracted to the system because of its regenerative abilities-if large portions of a cell are surgically removed, the remnant reorganizes into a normal-looking but smaller cell with correct proportionality [2, 3]...
February 20, 2017: Current Biology: CB
https://www.readbyqxmd.com/read/28182957/heteroagglomeration-of-zinc-oxide-nanoparticles-with-clay-mineral-modulates-the-bioavailability-and-toxicity-of-nanoparticle-in-tetrahymena-pyriformis
#18
Govind Sharan Gupta, Violet Aileen Senapati, Alok Dhawan, Rishi Shanker
The extensive use of zinc oxide nanoparticles (ZnO NPs) in cosmetics, sunscreens and healthcare products increases their release in the aquatic environment. The present study explored the possible interaction of ZnO NPs with montmorillonite clay minerals in aqueous conditions. An addition of ZnO NPs on clay suspension significantly (p<0.05) increases the hydrodymic size of clay particles from 1652±90nm to 2158±13nm due to heteroagglomeration. The electrokinetic measurements showed a significant (p<0...
June 1, 2017: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/28153088/specific-and-efficient-regression-of-cancers-harboring-kras-mutation-by-targeted-rna-replacement
#19
Sung Jin Kim, Ju Hyun Kim, Bitna Yang, Jin-Sook Jeong, Seong-Wook Lee
Mutations in the KRAS gene, which persistently activate RAS function, are most frequently found in many types of human cancers. Here, we proposed and verified a new approach against cancers harboring the KRAS mutation with high cancer selectivity and efficient anti-cancer effects based on targeted RNA replacement. To this end, trans-splicing ribozymes from Tetrahymena group I intron were developed, which can specifically target and reprogram the mutant KRAS G12V transcript to induce therapeutic gene activity in cells...
February 1, 2017: Molecular Therapy: the Journal of the American Society of Gene Therapy
https://www.readbyqxmd.com/read/28135687/n-6-methyladenine-dna-modification-in-the-unicellular-eukaryotic-organism-tetrahymena-thermophila
#20
REVIEW
Yuanyuan Wang, Yalan Sheng, Yongqiang Liu, Bo Pan, Jie Huang, Alan Warren, Shan Gao
N(6)-methyladenine DNA (6mA) modification exists in both prokaryotes and eukaryotes in which it plays a crucial role in regulating numerous biological processes. In prokaryotes, 6mA is a marker to distinguish self from foreign DNA. Its role in eukaryotes, however, remains elusive. Ciliates were among the first eukaryotes reported to contain 6mA. In the model organism T. thermophila, cellular localization and features of 6mA have been extensively studied, especially in ribosomal DNA (rDNA) molecules. Here, we summarize the features and potential functions of 6mA in Tetrahymena thermophila and other ciliates, and the major findings and contributions of the Tetrahymena model in studies of 6mA methylation...
April 2017: European Journal of Protistology
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