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  • Elsevier (CrossRef)  (12)
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  • 1
    Language: English
    In: Biochemical and Biophysical Research Communications, 23 March 2012, Vol.419(4), pp.698-702
    Description: ► Characterization of the proliferating cell nuclear antigen in (TbPCNA). ► TbPCNA is a suitable marker to detect replication in . ► TbPCNA distribution and regulation is different compared to closely related parasites and . As in most eukaryotic cells, replication is regulated by a conserved group of proteins in the early-diverged parasite . Only a few components of the replication machinery have been described in this parasite and regulation, sub-nuclear localization and timing of replication are not well understood. We characterized the proliferating cell nuclear antigen in (TbPCNA) to establish a spatial and temporal marker for replication. Interestingly, PCNA distribution and regulation is different compared to the closely related parasites and . TbPCNA foci are clearly detectable during S phase of the cell cycle but in contrast to they are not preferentially located at the nuclear periphery. Furthermore, PCNA seems to be degraded when cells enter G2 phase in suggesting different modes of replication regulation or functions of PCNA in these closely related eukaryotes.
    Keywords: Pcna ; Replication ; S Phase Marker ; Cell Cycle Regulation ; Trypanosoma Brucei ; Biology ; Chemistry ; Anatomy & Physiology
    ISSN: 0006-291X
    E-ISSN: 1090-2104
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  • 2
    Language: English
    In: Biochemical and Biophysical Research Communications, 2008, Vol.368(4), pp.846-851
    Description: Some inroads have been made into characterizing histone variants and post translational modifications of histones in . Histone variant H2BV lysine 129 is homologous to H2B lysine 123, whose ubiquitination is required for methylation of H3 lysines 4 and 79. We show that H2BV K129 is not ubiquitinated, but trimethylation of H3 K4 and K76, homologs of H3 K4 and K79 in yeast, was enriched in nucleosomes containing H2BV. Mutation of H2BV K129 to alanine or arginine did not disrupt H3 K4 or K76 methylation. These data suggest that H3 K4 and K76 methylation in trypanosomes is regulated by a novel mechanism, possibly involving the replacement of H2B with H2BV in the nucleosome.
    Keywords: Chromatin Structure ; Histone Methylation ; Histone Modification ; Histone Ubiquitination ; Histone Variant ; Mass Spectrometry ; Nucleosome ; Trypanosoma Brucei ; Biology ; Chemistry ; Anatomy & Physiology
    ISSN: 0006-291X
    E-ISSN: 1090-2104
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  • 3
    Language: English
    In: Molecular & Biochemical Parasitology, February 2011, Vol.175(2), pp.205-208
    Description: ▶ A reliable protocol to quantify cell-cycle dependent mRNA levels. ▶ Development and validation of an external standard for normalization. ▶ Transient up-regulation of a set of mRNAs during S and G2/M phase. Very little is known about cell cycle-dependent regulation of mRNA in , the causative agent of African sleeping sickness. Methods to synchronize cell cycle progression are inefficient or subject the parasites to non-physiological conditions and stress. We developed a fluorescence-activated cell sorting-based method to analyze steady-state mRNA levels in individual cell cycle phases. Normalization of the data was the most challenging problem because internal standards for cell cycle-regulated genes are not available for trypanosomes. Hence, we introduced an external standard (so-called “spike”) to compensate for technically derived variations in processing cells and RNA samples. Validation of this method with a limited number of genes unraveled a transient up-regulation during S and G2/M phases for all mRNAs analyzed.
    Keywords: Qpcr ; Trypanosoma Brucei ; Cell Cycle ; Mrna Expression ; FACS ; Biology ; Chemistry ; Zoology
    ISSN: 0166-6851
    E-ISSN: 1872-9428
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  • 4
    Language: English
    In: FEBS Letters, 2006, Vol.580(9), pp.2306-2310
    Description: To start to understand the role of chromatin structure in regulating transcription in trypanosomes, we analyzed covalent modifications on the four core histones of . We found unusually few modifications in the N-terminal tails, which are abundantly modified in other organisms and whose sequences, but not composition, are highly divergent in trypanosomes. In contrast, the C-terminal region of H2A appears to be hyper-acetylated. Surprisingly, the N-terminal alanines of H2A, H2B, and H4, were mono-methylated, a modification that has not been described previously for histones. Possible functions and evolutionary explanations for these unusual histone modifications are discussed.
    Keywords: Histone Methylation ; Histone Acetylation ; Histone Modification ; Mass Spectrometry ; Edman ; Trypanosoma Brucei ; Biology ; Chemistry ; Anatomy & Physiology
    ISSN: 0014-5793
    E-ISSN: 1873-3468
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  • 5
    Language: English
    In: Molecular Cell, 2006, Vol.23(4), pp.497-507
    Description: DOT1 is an evolutionarily conserved histone H3 lysine 79 (H3K79) methyltransferase. K79 methylation is associated with transcriptional activation, meiotic checkpoint control, and DNA double-strand break (DSB) responses. has two homologs, DOT1A and DOT1B, which are responsible for dimethylation and trimethylation of H3K76, respectively (K76 in is synonymous to K79 in other organisms). K76 dimethylation is only detectable during mitosis, whereas trimethylation occurs throughout the cell cycle. Deletion of DOT1B resulted in dimethylation of K76 throughout the cell cycle and caused subtle defects in cell cycle regulation and impaired differentiation. RNAi-mediated depletion of DOT1A appears to disrupt a mitotic checkpoint, resulting in premature progression through mitosis without DNA replication, generating a high proportion of cells with a haploid DNA content, an unprecedented state for trypanosomes. We propose that DOT1A and DOT1B influence the trypanosome cell cycle by regulating the degree of H3K76 methylation.
    Keywords: Microbio ; DNA ; Biology
    ISSN: 1097-2765
    E-ISSN: 1097-4164
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  • 6
    Language: English
    In: Experimental Parasitology, 2007, Vol.117(1), pp.111-114
    Description: Using green fluorescent protein as a reporter, we have shown that the strain 29–13 of , widely used for inducible down-regulation of mRNA, is inducible in, but not permissive for the tsetse flies and . Within two weeks post-infection, 42% males and females of teneral and non-teneral tsetse flies harboured intestinal infections, yet not a single infection progressed into the salivary glands.
    Keywords: Trypanosoma Brucei ; Tsetse ; Glossina ; Gfp ; Transmission ; Midgut Infection ; Tetracycline Induction ; Biology ; Zoology
    ISSN: 0014-4894
    E-ISSN: 1090-2449
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  • 7
    Language: English
    In: Molecular & Biochemical Parasitology, 2006, Vol.149(1), pp.102-107
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.molbiopara.2006.04.005 Byline: Christian J. Janzen (a), Frederick van Deursen (b), Huafang Shi (c), George A.M. Cross (a), Keith R. Matthews (b), Elisabetta Ullu (c)(d) Keywords: Trypanosomes; RNA interference; TbAGO1; VSG; Life-cycle Author Affiliation: (a) Laboratory of Molecular Parasitology, The Rockefeller University, Box 185, 1230 York Avenue, New York, NY 10021-6399, USA (b) Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JT, UK (c) Department of Internal Medicine, Yale Medical School, BCMM 136D, 295 Congress Avenue, Box 9812, New Haven, CT, 06536-8012, USA (d) Department of Cell Biology, Yale Medical School, BCMM 136D, 295 Congress Avenue, Box 9812, New Haven, CT, 06536-8012, USA Article History: Received 26 February 2006; Revised 1 April 2006; Accepted 7 April 2006
    Keywords: Trypanosomes ; RNA Interference ; Tbago1 ; Vsg ; Life-Cycle ; Biology ; Chemistry ; Zoology
    ISSN: 0166-6851
    E-ISSN: 1872-9428
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  • 8
    Language: English
    In: Molecular & Biochemical Parasitology, 2007, Vol.156(1), pp.41-50
    Description: Several biological processes in are affected by chromatin structure, including gene expression, cell cycle regulation, and life-cycle stage differentiation. In and other organisms, chromatin structure is dependent upon posttranslational modifications of histones, which have been mapped in detail. The tails of the four core histones of are highly diverged from those of mammals and yeasts, so sites of potential modification cannot be reliably inferred, and no cross-species antibodies are available to map the modifications. We therefore undertook an extensive survey to identify posttranslational modifications by Edman degradation and mass spectrometry. Edman analysis showed that the N-terminal alanine of H2A, H2B, and H4 could be monomethylated. We found that the histone H4 N-terminus is heavily modified, while, in contrast to other organisms, the histone H2A and H2B N-termini have relatively few modifications. Histone H3 appears to have a number of modifications at the N-terminus, but we were unable to assign many of these to a specific amino acid. Therefore, we focused our efforts on uncovering modification states of H4. We discuss the potential relevance of these modifications.
    Keywords: Trypanosoma Brucei ; Histone Acetylation ; Histone Methylation ; Transcription ; Nucleosome ; Chromatin ; Biology ; Chemistry ; Zoology
    ISSN: 0166-6851
    E-ISSN: 1872-9428
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  • 9
    Language: English
    In: Cognition, 2011, Vol.119(1), pp.70-80
    Description: The present paper explores cross-cultural variation in spatial cognition by comparing spatial reconstruction tasks by Dutch and Namibian elementary school children. These two communities differ in the way they predominantly express spatial relations in language. Four experiments investigate cognitive strategy preferences across different levels of task-complexity and instruction. Data show a correlation between dominant linguistic spatial frames of reference and performance patterns in non-linguistic spatial memory tasks. This correlation is shown to be stable across an increase of complexity in the spatial array. When instructed to use their respective non-habitual cognitive strategy, participants were not easily able to switch between strategies and their attempts to do so impaired their performance. These results indicate a difference not only in preference but also in competence and suggest that spatial language and non-linguistic preferences and competences in spatial cognition are systematically aligned across human populations.
    Keywords: Cross-Cultural Differences ; Spatial Cognition ; Psychology
    ISSN: 0010-0277
    E-ISSN: 18737838
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  • 10
    Language: English
    In: Theoretical population biology, May 2015, Vol.101, pp.31-9
    Description: Body size of vertebrate herbivores is strongly linked to other life history traits, most notably (1) tolerance of low quality forage and (2) vulnerability to predation, which both impact the composition and dynamics of natural communities. However, no study has thus far explored how the combination of these two body-size related traits affects the long-term composition and dynamics of the herbivore and plant communities. We made a simple model of ordinary differential equations and simulated a grassland system with three herbivore species (small, medium, large) and two predator species (small, large) to investigate how the combination of low-quality tolerance and predation-vulnerability structure the herbivore and plant community. We found that facilitation and competition between different-sized herbivores and predation by especially small predators stimulate coexistence among herbivore species. Furthermore, the interaction between different-sized herbivores and predators generated cyclical succession in the plant community, i.e. alternating periods of short vegetation dominated by high-quality plants, with periods of tall vegetation dominated by low-quality plants. Our results suggest that cyclical succession in plant communities is more likely to occur when a predator predominantly preys on small herbivore species. Large predators also play an important role, as their addition relaxed the set of conditions under which cyclical succession occurred. Consequently, our model predictions suggest that a diverse predator community plays an important role in the long-term dynamics and maintenance of diversity in both the herbivore and plant community.
    Keywords: Facilitation ; Lotka–Volterra ; Plant–Herbivore Interaction ; Predator–Prey Model ; Shifting Mosaic ; Vegetation Dynamics ; Ecosystem ; Herbivory ; Models, Biological ; Plants ; Predatory Behavior
    ISSN: 00405809
    E-ISSN: 1096-0325
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