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Radhakrishnan A, Gangopadhyay R, Sharma C, Kapardar RK, Sharma NK, Srivastav R. Unwinding Helicase MCM Functionality for Diagnosis and Therapeutics of Replication Abnormalities Associated with Cancer: A Review. Mol Diagn Ther 2024; 28:249-264. [PMID: 38530633 DOI: 10.1007/s40291-024-00701-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/28/2024] [Indexed: 03/28/2024]
Abstract
The minichromosome maintenance (MCM) protein is a component of an active helicase that is essential for the initiation of DNA replication. Dysregulation of MCM functions contribute to abnormal cell proliferation and genomic instability. The interactions of MCM with cellular factors, including Cdc45 and GINS, determine the formation of active helicase and functioning of helicase. The functioning of MCM determines the fate of DNA replication and, thus, genomic integrity. This complex is upregulated in precancerous cells and can act as an important tool for diagnostic applications. The MCM protein complex can be an important broad-spectrum therapeutic target in various cancers. Investigations have supported the potential and applications of MCM in cancer diagnosis and its therapeutics. In this article, we discuss the physiological roles of MCM and its associated factors in DNA replication and cancer pathogenesis.
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Affiliation(s)
| | - Ritwik Gangopadhyay
- Amity Institute of Biotechnology, Amity University, Noida, Uttar Pradesh, India
| | | | | | - Nilesh Kumar Sharma
- Cancer and Translational Research Lab, Dr. DY Patil Biotechnology and Bioinformatics Institute, Dr. DY Patil Vidyapeeth, Pune, Maharashtra, India
| | - Rajpal Srivastav
- Amity Institute of Biotechnology, Amity University, Noida, Uttar Pradesh, India.
- Department of Science and Technology, Ministry of Science and Technology, New Delhi, India.
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2
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Briggs EM, Marques CA, Oldrieve GR, Hu J, Otto TD, Matthews KR. Profiling the bloodstream form and procyclic form Trypanosoma brucei cell cycle using single-cell transcriptomics. eLife 2023; 12:e86325. [PMID: 37166108 PMCID: PMC10212563 DOI: 10.7554/elife.86325] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Accepted: 05/10/2023] [Indexed: 05/12/2023] Open
Abstract
African trypanosomes proliferate as bloodstream forms (BSFs) and procyclic forms in the mammal and tsetse fly midgut, respectively. This allows them to colonise the host environment upon infection and ensure life cycle progression. Yet, understanding of the mechanisms that regulate and drive the cell replication cycle of these forms is limited. Using single-cell transcriptomics on unsynchronised cell populations, we have obtained high resolution cell cycle regulated (CCR) transcriptomes of both procyclic and slender BSF Trypanosoma brucei without prior cell sorting or synchronisation. Additionally, we describe an efficient freeze-thawing protocol that allows single-cell transcriptomic analysis of cryopreserved T. brucei. Computational reconstruction of the cell cycle using periodic pseudotime inference allowed the dynamic expression patterns of cycling genes to be profiled for both life cycle forms. Comparative analyses identify a core cycling transcriptome highly conserved between forms, as well as several genes where transcript levels dynamics are form specific. Comparing transcript expression patterns with protein abundance revealed that the majority of genes with periodic cycling transcript and protein levels exhibit a relative delay between peak transcript and protein expression. This work reveals novel detail of the CCR transcriptomes of both forms, which are available for further interrogation via an interactive webtool.
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Affiliation(s)
- Emma M Briggs
- Institute for Immunology and Infection Research, School of Biological Sciences, University of EdinburghEdinburghUnited Kingdom
- Wellcome Centre for Integrative Parasitology, School of Infection & Immunity, University of GlasgowGlasgowUnited Kingdom
| | - Catarina A Marques
- Wellcome Centre for Integrative Parasitology, School of Infection & Immunity, University of GlasgowGlasgowUnited Kingdom
| | - Guy R Oldrieve
- Institute for Immunology and Infection Research, School of Biological Sciences, University of EdinburghEdinburghUnited Kingdom
| | - Jihua Hu
- Institute for Immunology and Infection Research, School of Biological Sciences, University of EdinburghEdinburghUnited Kingdom
| | - Thomas D Otto
- Wellcome Centre for Integrative Parasitology, School of Infection & Immunity, University of GlasgowGlasgowUnited Kingdom
| | - Keith R Matthews
- Institute for Immunology and Infection Research, School of Biological Sciences, University of EdinburghEdinburghUnited Kingdom
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3
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Fu Y, Lv Z, Kong D, Fan Y, Dong B. High abundance of CDC45 inhibits cell proliferation through elevation of HSPA6. Cell Prolif 2022; 55:e13257. [PMID: 35642733 PMCID: PMC9251052 DOI: 10.1111/cpr.13257] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2022] [Revised: 04/15/2022] [Accepted: 04/25/2022] [Indexed: 11/29/2022] Open
Abstract
OBJECTIVES CDC45 is the core component of CMG (CDC45-MCMs-GINS) complex that plays important role in the initial step of DNA replication in eukaryotic cells. The expression level of cdc45 is under the critical control for the accurate cell cycle progression. Loss-of-function of cdc45 has been demonstrated to inhibit cell proliferation and leads to cell death due to the inhibition of DNA replication and G1-phase arrest. An increasing of CDC45 inhibits cell proliferation as well. Nevertheless, a systematic analysis of the effect of high dose of CDC45 on cell physiology and behaviors is unclear. In the present study, we aimed to investigate the effects and mechanisms of high dose of CDC45 on cell behaviors. MATERIALS AND METHODS We overexpressed cdc45 in cultured cell lines, Ciona and Drosophila embryos, respectively. The cell cycle progression was examined by the BrdU incorporation experiment, flow cytometry and PH3 (phospho-Histone 3) staining. RNA-sequencing analysis and qRT-PCR were carried out to screen the affected genes in HeLa cells overexpressing cdc45. siRNA-mediated knockdown was performed to investigate gene functions in HeLa cells overexpressing cdc45. RESULTS We found that high level of cdc45 from different species (human, mammal, ascidian, and Drosophila) inhibited cell cycle in vitro and in vivo. High dose of CDC45 blocks cells entering into S phase. However, we failed to detect DNA damage and cell apoptosis. We identified hspa6 was the most upregulated gene in HeLa cells overexpressing cdc45 via RNA-seq analysis and qRT-PCR validation. Overexpression of Hs-hspa6 inhibited proliferation rate and DNA replication in HeLa cells, mimicking the phenotype of cdc45 overexpression. RNAi against hspa6 partially rescued the cell proliferation defect caused by high dose of CDC45. CONCLUSIONS Our study suggests that high abundance of CDC45 stops cell cycle. Instead of inducing apoptosis, excessive CDC45 prevents cell entering S phase probably due to promoting hspa6 expression.
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Affiliation(s)
- Yuanyuan Fu
- Sars‐Fang Centre, MoE Key Laboratory of Marine Genetics and BreedingCollege of Marine Life Sciences, Ocean University of ChinaQingdaoChina
| | - Zhiyi Lv
- Sars‐Fang Centre, MoE Key Laboratory of Marine Genetics and BreedingCollege of Marine Life Sciences, Ocean University of ChinaQingdaoChina
- Institute of Evolution & Marine BiodiversityOcean University of ChinaQingdaoChina
| | - Deqing Kong
- Department of BiologyPhilipps UniversityMarburgGermany
| | - Yuping Fan
- Sars‐Fang Centre, MoE Key Laboratory of Marine Genetics and BreedingCollege of Marine Life Sciences, Ocean University of ChinaQingdaoChina
| | - Bo Dong
- Sars‐Fang Centre, MoE Key Laboratory of Marine Genetics and BreedingCollege of Marine Life Sciences, Ocean University of ChinaQingdaoChina
- Institute of Evolution & Marine BiodiversityOcean University of ChinaQingdaoChina
- Laboratory for Marine Biology and BiotechnologyQingdao National Laboratory for Marine Science and TechnologyQingdaoChina
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4
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Lee KJ, Li Z. The CRK2-CYC13 complex functions as an S-phase cyclin-dependent kinase to promote DNA replication in Trypanosoma brucei. BMC Biol 2021; 19:29. [PMID: 33568178 PMCID: PMC7876812 DOI: 10.1186/s12915-021-00961-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Accepted: 01/15/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Faithful DNA replication is essential to maintain genomic stability in all living organisms, and the regulatory pathway for DNA replication initiation is conserved from yeast to humans. The evolutionarily ancient human parasite Trypanosoma brucei, however, lacks many of the conserved DNA replication factors and may employ unusual mechanisms for DNA replication. Neither the S-phase cyclin-dependent kinase (CDK) nor the regulatory pathway governing DNA replication has been previously identified in T. brucei. RESULTS Here we report that CRK2 (Cdc2-related kinase 2) complexes with CYC13 (Cyclin13) and functions as an S-phase CDK to promote DNA replication in T. brucei. We further show that CRK2 phosphorylates Mcm3, a subunit of the Mcm2-7 sub-complex of the Cdc45-Mcm2-7-GINS complex, and demonstrate that Mcm3 phosphorylation by CRK2 facilitates interaction with Sld5, a subunit of the GINS sub-complex of the Cdc45-Mcm2-7-GINS complex. CONCLUSIONS These results identify the CRK2-CYC13 complex as an S-phase regulator in T. brucei and reveal its role in regulating DNA replication through promoting the assembly of the Cdc45-Mcm2-7-GINS complex.
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Affiliation(s)
- Kyu Joon Lee
- Department of Microbiology and Molecular Genetics, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, 77030, USA
| | - Ziyin Li
- Department of Microbiology and Molecular Genetics, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, 77030, USA.
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DNA replication protein Cdc45 directly interacts with PCNA via its PIP box in Leishmania donovani and the Cdc45 PIP box is essential for cell survival. PLoS Pathog 2020; 16:e1008190. [PMID: 32413071 PMCID: PMC7255605 DOI: 10.1371/journal.ppat.1008190] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 05/28/2020] [Accepted: 04/16/2020] [Indexed: 12/22/2022] Open
Abstract
DNA replication protein Cdc45 is an integral part of the eukaryotic replicative helicase whose other components are the Mcm2-7 core, and GINS. We identified a PIP box motif in Leishmania donovani Cdc45. This motif is typically linked to interaction with the eukaryotic clamp proliferating cell nuclear antigen (PCNA). The homotrimeric PCNA can potentially bind upto three different proteins simultaneously via a loop region present in each monomer. Multiple binding partners have been identified from among the replication machinery in other eukaryotes, and the concerted /sequential binding of these partners are central to the fidelity of the replication process. Though conserved in Cdc45 across Leishmania species and Trypanosoma cruzi, the PIP box is absent in Trypanosoma brucei Cdc45. Here we investigate the possibility of Cdc45-PCNA interaction and the role of such an interaction in the in vivo context. Having confirmed the importance of Cdc45 in Leishmania DNA replication we establish that Cdc45 and PCNA interact stably in whole cell extracts, also interacting with each other directly in vitro. The interaction is mediated via the Cdc45 PIP box. This PIP box is essential for Leishmania survival. The importance of the Cdc45 PIP box is also examined in Schizosaccharomyces pombe, and it is found to be essential for cell survival here as well. Our results implicate a role for the Leishmania Cdc45 PIP box in recruiting or stabilizing PCNA on chromatin. The Cdc45-PCNA interaction might help tether PCNA and associated replicative DNA polymerase to the DNA template, thus facilitating replication fork elongation. Though multiple replication proteins that associate with PCNA have been identified in other eukaryotes, this is the first report demonstrating a direct interaction between Cdc45 and PCNA, and while our analysis suggests the interaction may not occur in human cells, it indicates that it may not be confined to trypanosomatids.
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Butenko A, Opperdoes FR, Flegontova O, Horák A, Hampl V, Keeling P, Gawryluk RMR, Tikhonenkov D, Flegontov P, Lukeš J. Evolution of metabolic capabilities and molecular features of diplonemids, kinetoplastids, and euglenids. BMC Biol 2020; 18:23. [PMID: 32122335 PMCID: PMC7052976 DOI: 10.1186/s12915-020-0754-1] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Accepted: 02/17/2020] [Indexed: 12/24/2022] Open
Abstract
Background The Euglenozoa are a protist group with an especially rich history of evolutionary diversity. They include diplonemids, representing arguably the most species-rich clade of marine planktonic eukaryotes; trypanosomatids, which are notorious parasites of medical and veterinary importance; and free-living euglenids. These different lifestyles, and particularly the transition from free-living to parasitic, likely require different metabolic capabilities. We carried out a comparative genomic analysis across euglenozoan diversity to see how changing repertoires of enzymes and structural features correspond to major changes in lifestyles. Results We find a gradual loss of genes encoding enzymes in the evolution of kinetoplastids, rather than a sudden decrease in metabolic capabilities corresponding to the origin of parasitism, while diplonemids and euglenids maintain more metabolic versatility. Distinctive characteristics of molecular machines such as kinetochores and the pre-replication complex that were previously considered specific to parasitic kinetoplastids were also identified in their free-living relatives. Therefore, we argue that they represent an ancestral rather than a derived state, as thought until the present. We also found evidence of ancient redundancy in systems such as NADPH-dependent thiol-redox. Only the genus Euglena possesses the combination of trypanothione-, glutathione-, and thioredoxin-based systems supposedly present in the euglenozoan common ancestor, while other representatives of the phylum have lost one or two of these systems. Lastly, we identified convergent losses of specific metabolic capabilities between free-living kinetoplastids and ciliates. Although this observation requires further examination, it suggests that certain eukaryotic lineages are predisposed to such convergent losses of key enzymes or whole pathways. Conclusions The loss of metabolic capabilities might not be associated with the switch to parasitic lifestyle in kinetoplastids, and the presence of a highly divergent (or unconventional) kinetochore machinery might not be restricted to this protist group. The data derived from the transcriptomes of free-living early branching prokinetoplastids suggests that the pre-replication complex of Trypanosomatidae is a highly divergent version of the conventional machinery. Our findings shed light on trends in the evolution of metabolism in protists in general and open multiple avenues for future research.
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Affiliation(s)
- Anzhelika Butenko
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic.,Faculty of Science, University of Ostrava, Ostrava, Czech Republic
| | - Fred R Opperdoes
- de Duve Institute, Université Catholique de Louvain, Brussels, Belgium
| | - Olga Flegontova
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic.,Faculty of Science, University of Ostrava, Ostrava, Czech Republic
| | - Aleš Horák
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic.,Faculty of Science, University of South Bohemia, České Budějovice (Budweis), Czech Republic
| | - Vladimír Hampl
- Faculty of Science, Charles University, Biocev, Vestec, Czech Republic
| | - Patrick Keeling
- Department of Botany, University of British Columbia, Vancouver, Canada
| | | | - Denis Tikhonenkov
- Department of Botany, University of British Columbia, Vancouver, Canada.,Papanin Institute for Biology of Inland Waters, Russian Academy of Sciences, Borok, Russia
| | - Pavel Flegontov
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic. .,Faculty of Science, University of Ostrava, Ostrava, Czech Republic. .,Present address: Department of Genetics, Harvard Medical School, Boston, USA.
| | - Julius Lukeš
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic. .,Faculty of Science, University of South Bohemia, České Budějovice (Budweis), Czech Republic.
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7
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Sloan MA, Brooks K, Otto TD, Sanders MJ, Cotton JA, Ligoxygakis P. Transcriptional and genomic parallels between the monoxenous parasite Herpetomonas muscarum and Leishmania. PLoS Genet 2019; 15:e1008452. [PMID: 31710597 PMCID: PMC6872171 DOI: 10.1371/journal.pgen.1008452] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 11/21/2019] [Accepted: 10/01/2019] [Indexed: 12/20/2022] Open
Abstract
Trypanosomatid parasites are causative agents of important human and animal diseases such as sleeping sickness and leishmaniasis. Most trypanosomatids are transmitted to their mammalian hosts by insects, often belonging to Diptera (or true flies). These are called dixenous trypanosomatids since they infect two different hosts, in contrast to those that infect just insects (monoxenous). However, it is still unclear whether dixenous and monoxenous trypanosomatids interact similarly with their insect host, as fly-monoxenous trypanosomatid interaction systems are rarely reported and under-studied-despite being common in nature. Here we present the genome of monoxenous trypanosomatid Herpetomonas muscarum and discuss its transcriptome during in vitro culture and during infection of its natural insect host Drosophila melanogaster. The H. muscarum genome is broadly syntenic with that of human parasite Leishmania major. We also found strong similarities between the H. muscarum transcriptome during fruit fly infection, and those of Leishmania during sand fly infections. Overall this suggests Drosophila-Herpetomonas is a suitable model for less accessible insect-trypanosomatid host-parasite systems such as sand fly-Leishmania.
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Affiliation(s)
- Megan A. Sloan
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Karen Brooks
- The Wellcome Sanger Institute, Wellcome Genome Campus, Hixton, Cambridgeshire, United Kingdom
| | - Thomas D. Otto
- The Wellcome Sanger Institute, Wellcome Genome Campus, Hixton, Cambridgeshire, United Kingdom
| | - Mandy J. Sanders
- The Wellcome Sanger Institute, Wellcome Genome Campus, Hixton, Cambridgeshire, United Kingdom
| | - James A. Cotton
- The Wellcome Sanger Institute, Wellcome Genome Campus, Hixton, Cambridgeshire, United Kingdom
| | - Petros Ligoxygakis
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
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Zhu Z, Yu Z, Rong Z, Luo Z, Zhang J, Qiu Z, Huang C. The novel GINS4 axis promotes gastric cancer growth and progression by activating Rac1 and CDC42. Theranostics 2019; 9:8294-8311. [PMID: 31754397 PMCID: PMC6857050 DOI: 10.7150/thno.36256] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Accepted: 09/15/2019] [Indexed: 12/20/2022] Open
Abstract
Rationale: As a component of GINS complex, GINS4 is essential for initiating DNA replication and elongation of the cell cycle G1/S phase in eukaryotes and plays a vital role in normal physiological processes. However, the precise functions and regulation mechanisms of GINS4 in human tumors remain elusive. Methods: GINS4 expression was analyzed in gastric cancer tissues by qRT-PCR and western blotting, and its clinical relevance was studied using TMA. The biological functions of GINS4 were detected in vitro and in vivo. cDNA array, co-IP, GST pull-down and GTPase activation assays were performed to investigate the downstream regulation mechanism of GINS4. Upstream regulation mechanism of GINS4 was explored and demonstrated by circRNA sequencing, bioinformatics analysis, luciferase reporter assay and rescue experiments. Results: Strikingly high GINS4 expression was detected in gastric cancer tissues and correlated with poor differentiation, advanced tumor stage, invasion depth and lymph node metastasis. GINS4 promoted cell growth and metastasis in vitro and in vivo, and suppressed cell apoptosis in vitro. Mechanistically, GINS4 activated Rac1/CDC42 through directly binding to Rac1/CDC42, thereby activating their downstream pathways. Furthermore, circMLLT10 acts as a miR-509-3-5p sponge to attenuate its repressive effect on target GINS4. In addition, circMLLT10 promoted cell growth and metastasis and suppressed cell apoptosis, whereas miR-509-3-5p inhibited cell growth and metastasis and promoted cell apoptosis. Conclusion: The findings indicate for the first time that the novel GINS4 axis promotes gastric cancer cell growth and progression by activating Rac1 and CDC42. GINS4 may be a promising biomarker and target for diagnosis and treatment of gastric cancer.
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Abstract
Trypanosomes have complex life cycles within which there are both proliferative and differentiation cell divisions. The coordination of the cell cycle to achieve these different divisions is critical for the parasite to infect both host and vector. From studying the regulation of the proliferative cell cycle of the Trypanosoma brucei procyclic life cycle stage, three subcycles emerge that control the duplication and segregation of ( a) the nucleus, ( b) the kinetoplast, and ( c) a set of cytoskeletal structures. We discuss how the clear dependency relationships within these subcycles, and the potential for cross talk between them, are likely required for overall cell cycle coordination. Finally, we look at the implications this interdependence has for proliferative and differentiation divisions through the T. brucei life cycle and in related parasitic trypanosomatid species.
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Affiliation(s)
- Richard J. Wheeler
- Nuffield Department of Medicine, University of Oxford, Oxford OX1 3SY, United Kingdom
| | - Keith Gull
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, United Kingdom
| | - Jack D. Sunter
- Department of Biological and Medical Sciences, Oxford Brookes University, Oxford OX3 0BP, United Kingdom
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10
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Kim HS. Genome-wide function of MCM-BP in Trypanosoma brucei DNA replication and transcription. Nucleic Acids Res 2019; 47:634-647. [PMID: 30407533 PMCID: PMC6344857 DOI: 10.1093/nar/gky1088] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Accepted: 10/21/2018] [Indexed: 12/13/2022] Open
Abstract
In Trypanosoma brucei, genes are arranged in Polycistronic Transcription Units (PTUs), which are demarcated by transcription start and stop sites. Transcription start sites are also binding sites of Origin Recognition Complex 1 (ORC1). This spatial coincidence implies that transcription and replication in trypanosomes must occur in a highly ordered and cooperative manner. Interestingly, a previously published genetic screen identified the T. brucei MCM-BP, which interacts with subunits of MCM helicase, as a protein whose downregulation results in the loss of transcriptional silencing at subtelomeric loci. Here, I show that TbMCM-BP is required for DNA replication and transcription. TbMCM-BP depletion causes a significant reduction of replicating cells in S phase and genome-wide impairments of replication origin activation. Moreover, levels of sense and antisense transcripts increase at boundaries of PTUs in the absence of TbMCM-BP. TbMCM-BP is also important for transcriptional repression of the specialized subtelomeric PTUs, the Bloodstream-form Expression-Sites (BESs), which house the major antigenic determinant (the Variant Surface Glycoprotein, VSG gene) as well as TbORC1 binding sites. Overall, this study reveals that TbMCM-BP, a replication initiation protein, also guides the initiation, termination and directionality of transcription.
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Affiliation(s)
- Hee-Sook Kim
- Laboratory of Lymphocyte Biology, Rockefeller University, 1275 York Avenue, New York, NY 10065, USA.,Department of Biological, Geological, and Environmental Sciences, Center for Gene Regulation in Health and Disease, Cleveland State University, 2121 Euclid Avenue, Cleveland, OH 44115, USA
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11
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Vesteg M, Hadariová L, Horváth A, Estraño CE, Schwartzbach SD, Krajčovič J. Comparative molecular cell biology of phototrophic euglenids and parasitic trypanosomatids sheds light on the ancestor of Euglenozoa. Biol Rev Camb Philos Soc 2019; 94:1701-1721. [PMID: 31095885 DOI: 10.1111/brv.12523] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Revised: 04/30/2019] [Accepted: 05/02/2019] [Indexed: 01/23/2023]
Abstract
Parasitic trypanosomatids and phototrophic euglenids are among the most extensively studied euglenozoans. The phototrophic euglenid lineage arose relatively recently through secondary endosymbiosis between a phagotrophic euglenid and a prasinophyte green alga that evolved into the euglenid secondary chloroplast. The parasitic trypanosomatids (i.e. Trypanosoma spp. and Leishmania spp.) and the freshwater phototrophic euglenids (i.e. Euglena gracilis) are the most evolutionary distant lineages in the Euglenozoa phylogenetic tree. The molecular and cell biological traits they share can thus be considered as ancestral traits originating in the common euglenozoan ancestor. These euglenozoan ancestral traits include common mitochondrial presequence motifs, respiratory chain complexes containing various unique subunits, a unique ATP synthase structure, the absence of mitochondria-encoded transfer RNAs (tRNAs), a nucleus with a centrally positioned nucleolus, closed mitosis without dissolution of the nuclear membrane and nucleoli, a nuclear genome containing the unusual 'J' base (β-D-glucosyl-hydroxymethyluracil), processing of nucleus-encoded precursor messenger RNAs (pre-mRNAs) via spliced-leader RNA (SL-RNA) trans-splicing, post-transcriptional gene silencing by the RNA interference (RNAi) pathway and the absence of transcriptional regulation of nuclear gene expression. Mitochondrial uridine insertion/deletion RNA editing directed by guide RNAs (gRNAs) evolved in the ancestor of the kinetoplastid lineage. The evolutionary origin of other molecular features known to be present only in either kinetoplastids (i.e. polycistronic transcripts, compaction of nuclear genomes) or euglenids (i.e. monocistronic transcripts, huge genomes, many nuclear cis-spliced introns, polyproteins) is unclear.
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Affiliation(s)
- Matej Vesteg
- Department of Biology and Ecology, Faculty of Natural Sciences, Matej Bel University, 974 01, Banská Bystrica, Slovakia
| | - Lucia Hadariová
- Biotechnology and Biomedicine Center of the Academy of Sciences and Charles University in Vestec (BIOCEV), 252 50, Vestec, Czech Republic.,Department of Parasitology, Faculty of Science, Charles University in Prague, 128 44, Prague, Czech Republic
| | - Anton Horváth
- Department of Biochemistry, Faculty of Natural Sciences, Comenius University, 842 15, Bratislava, Slovakia
| | - Carlos E Estraño
- Department of Biological Sciences, University of Memphis, Memphis, TN, 38152-3560, USA
| | - Steven D Schwartzbach
- Department of Biological Sciences, University of Memphis, Memphis, TN, 38152-3560, USA
| | - Juraj Krajčovič
- Department of Biology, Faculty of Natural Sciences, University of ss. Cyril and Methodius, 917 01, Trnava, Slovakia
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12
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Marques CA, McCulloch R. Conservation and Variation in Strategies for DNA Replication of Kinetoplastid Nuclear Genomes. Curr Genomics 2018; 19:98-109. [PMID: 29491738 PMCID: PMC5814967 DOI: 10.2174/1389202918666170815144627] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2017] [Revised: 03/19/2017] [Accepted: 04/11/2017] [Indexed: 12/21/2022] Open
Abstract
Introduction: Understanding how the nuclear genome of kinetoplastid parasites is replicated received experimental stimulus from sequencing of the Leishmania major, Trypanosoma brucei and Trypanosoma cruzi genomes around 10 years ago. Gene annotations suggested key players in DNA replication initiation could not be found in these organisms, despite considerable conservation amongst characterised eukaryotes. Initial studies that indicated trypanosomatids might possess an archaeal-like Origin Recognition Complex (ORC), composed of only a single factor termed ORC1/CDC6, have been supplanted by the more recent identification of an ORC in T. brucei. However, the constituent subunits of T. brucei ORC are highly diverged relative to other eukaryotic ORCs and the activity of the complex appears subject to novel, positive regulation. The availability of whole genome sequences has also allowed the deployment of genome-wide strategies to map DNA replication dynamics, to date in T. brucei and Leishmania. ORC1/CDC6 binding and function in T. brucei displays pronounced overlap with the unconventional organisation of gene expression in the genome. Moreover, mapping of sites of replication initiation suggests pronounced differences in replication dynamics in Leishmania relative to T. brucei. Conclusion: Here we discuss what implications these emerging data may have for parasite and eukaryotic biology of DNA replication.
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Affiliation(s)
- Catarina A Marques
- Division of Biological Chemistry and Drug Discovery, School of Life Sciences, Dow Street, University of Dundee, Dundee, DD1 5EH, UK
| | - Richard McCulloch
- The Wellcome Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, Sir Graeme Davis Building, 120 University Place, University of Glasgow, Glasgow, G12 8TA, UK
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Cheung CHY, Hsu CL, Chen KP, Chong ST, Wu CH, Huang HC, Juan HF. MCM2-regulated functional networks in lung cancer by multi-dimensional proteomic approach. Sci Rep 2017; 7:13302. [PMID: 29038488 PMCID: PMC5643318 DOI: 10.1038/s41598-017-13440-x] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Accepted: 09/25/2017] [Indexed: 12/17/2022] Open
Abstract
DNA replication control is vital for maintaining genome stability and the cell cycle, perhaps most notably during cell division. Malignancies often exhibit defective minichromosome maintenance protein 2 (MCM2), a cancer proliferation biomarker that serves as a licensing factor in the initiation of DNA replication. MCM2 is also known to be one of the ATPase active sites that facilitates conformational changes and drives DNA unwinding at the origin of DNA replication. However, the biological networks of MCM2 in lung cancer cells via protein phosphorylation remain unmapped. The RNA-seq datasets from The Cancer Genome Atlas (TCGA) revealed that MCM2 overexpression is correlated with poor survival rate in lung cancer patients. To uncover MCM2-regulated functional networks in lung cancer, we performed multi-dimensional proteomic approach by integrating analysis of the phosphoproteome and proteome, and identified a total of 2361 phosphorylation sites on 753 phosphoproteins, and 4672 proteins. We found that the deregulation of MCM2 is involved in lung cancer cell proliferation, the cell cycle, and migration. Furthermore, HMGA1S99 phosphorylation was found to be differentially expressed under MCM2 perturbation in opposite directions, and plays an important role in regulating lung cancer cell proliferation. This study therefore enhances our capacity to therapeutically target cancer-specific phosphoproteins.
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Affiliation(s)
- Chantal Hoi Yin Cheung
- Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, 10617, Taiwan
| | - Chia-Lang Hsu
- Department of Life Science, National Taiwan University, Taipei, 10617, Taiwan
| | - Kai-Pu Chen
- Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, 10617, Taiwan
| | - Siao-Ting Chong
- Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, 10617, Taiwan
| | - Chang-Hsun Wu
- Department of Life Science, National Taiwan University, Taipei, 10617, Taiwan
| | - Hsuan-Cheng Huang
- Institute of Biomedical Informatics, Center for Systems and Synthetic Biology, National Yang-Ming University, Taipei, 11221, Taiwan.
| | - Hsueh-Fen Juan
- Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, 10617, Taiwan. .,Department of Life Science, National Taiwan University, Taipei, 10617, Taiwan. .,Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, 10617, Taiwan.
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14
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Nuclear DNA Replication in Trypanosomatids: There Are No Easy Methods for Solving Difficult Problems. Trends Parasitol 2017; 33:858-874. [PMID: 28844718 PMCID: PMC5662062 DOI: 10.1016/j.pt.2017.08.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Revised: 07/31/2017] [Accepted: 08/02/2017] [Indexed: 01/09/2023]
Abstract
In trypanosomatids, etiological agents of devastating diseases, replication is robust and finely controlled to maintain genome stability and function in stressful environments. However, these parasites encode several replication protein components and complexes that show potentially variant composition compared with model eukaryotes. This review focuses on the advances made in recent years regarding the differences and peculiarities of the replication machinery in trypanosomatids, including how such divergence might affect DNA replication dynamics and the replication stress response. Comparing the DNA replication machinery and processes of parasites and their hosts may provide a foundation for the identification of targets that can be used in the development of chemotherapies to assist in the eradication of diseases caused by these pathogens. In trypanosomatids, DNA replication is tightly controlled by protein complexes that diverge from those of model eukaryotes. There is no consensus for the number of replication origins used by trypanosomatids; how their replication dynamics compares with that of model organisms is the subject of debate. The DNA replication rate in trypanosomatids is similar to, but slightly higher than, that of model eukaryotes, which may be related to chromatin structure and function. Recent data suggest that the origin recognition complex in trypanosomatids closely resembles the multisubunit eukaryotic model. The absence of fundamental replication-associated proteins in trypanosomatids suggests that new signaling pathways may be present in these parasites to direct DNA replication and the replicative stress response.
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15
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Genome-wide and protein kinase-focused RNAi screens reveal conserved and novel damage response pathways in Trypanosoma brucei. PLoS Pathog 2017; 13:e1006477. [PMID: 28742144 PMCID: PMC5542689 DOI: 10.1371/journal.ppat.1006477] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Revised: 08/03/2017] [Accepted: 06/17/2017] [Indexed: 12/21/2022] Open
Abstract
All cells are subject to structural damage that must be addressed for continued growth. A wide range of damage affects the genome, meaning multiple pathways have evolved to repair or bypass the resulting DNA lesions. Though many repair pathways are conserved, their presence or function can reflect the life style of individual organisms. To identify genome maintenance pathways in a divergent eukaryote and important parasite, Trypanosoma brucei, we performed RNAi screens to identify genes important for survival following exposure to the alkylating agent methyl methanesulphonate. Amongst a cohort of broadly conserved and, therefore, early evolved repair pathways, we reveal multiple activities not so far examined functionally in T. brucei, including DNA polymerases, DNA helicases and chromatin factors. In addition, the screens reveal Trypanosoma- or kinetoplastid-specific repair-associated activities. We also provide focused analyses of repair-associated protein kinases and show that loss of at least nine, and potentially as many as 30 protein kinases, including a nuclear aurora kinase, sensitises T. brucei to alkylation damage. Our results demonstrate the potential for synthetic lethal genome-wide screening of gene function in T. brucei and provide an evolutionary perspective on the repair pathways that underpin effective responses to damage, with particular relevance for related kinetoplastid pathogens. By revealing that a large number of diverse T. brucei protein kinases act in the response to damage, we expand the range of eukaryotic signalling factors implicated in genome maintenance activities. Damage to the genome is a universal threat to life. Though the repair pathways used to tackle damage can be widely conserved, lineage-specific specialisations are found, reflecting the differing life styles of extant organisms. Using RNAi coupled with next generation sequencing we have screened for genes that are important for growth of Trypanosoma brucei, a diverged eukaryotic microbe and important parasite, in the presence of alkylation damage caused by methyl methanesulphonate. We reveal both repair pathway conservation relative to characterised eukaryotes and specialisation, including uncharacterised roles for translesion DNA polymerases, DNA helicases and chromatin factors. Furthermore, we demonstrate that loss of around 15% of T. brucei protein kinases sensitises the parasites to alkylation, indicating phosphorylation signalling plays widespread and under-investigated roles in the damage response pathways of eukaryotes.
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16
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da Silva MS, Muñoz PAM, Armelin HA, Elias MC. Differences in the Detection of BrdU/EdU Incorporation Assays Alter the Calculation for G1, S, and G2 Phases of the Cell Cycle in Trypanosomatids. J Eukaryot Microbiol 2017; 64:756-770. [PMID: 28258618 DOI: 10.1111/jeu.12408] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 02/17/2017] [Accepted: 02/23/2017] [Indexed: 01/22/2023]
Abstract
Trypanosomatids are the etiologic agents of various infectious diseases in humans. They diverged early during eukaryotic evolution and have attracted attention as peculiar models for evolutionary and comparative studies. Here, we show a meticulous study comparing the incorporation and detection of the thymidine analogs BrdU and EdU in Leishmania amazonensis, Trypanosoma brucei, and Trypanosoma cruzi to monitor their DNA replication. We used BrdU- and EdU-incorporated parasites with the respective standard detection approaches: indirect immunofluorescence to detect BrdU after standard denaturation (2 M HCl) and "click" chemistry to detect EdU. We found a discrepancy between these two thymidine analogs due to the poor detection of BrdU, which is reflected on the estimative of the duration of the cell cycle phases G1, S, and G2. To solve this discrepancy, we increase the exposure of incorporated BrdU using different concentrations of HCl. Using a new value for HCl concentration, we re-estimated the phases G1, S, G2 + M, and cytokinesis durations, confirming the values found by this approach using EdU. In conclusion, we suggest that the studies using BrdU with standard detection approach, not only in trypanosomatids but also in others cell types, should be reviewed to ensure an accurate estimation of DNA replication monitoring.
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Affiliation(s)
- Marcelo Santos da Silva
- Laboratório Especial de Ciclo Celular, Center of Toxins, Immune Response and Cell Signaling (CeTICS), Butantan Institute, 1500, Vital Brasil Avenue, 05503-900, São Paulo, Brazil
| | - Paula Andrea Marin Muñoz
- Laboratório Especial de Ciclo Celular, Center of Toxins, Immune Response and Cell Signaling (CeTICS), Butantan Institute, 1500, Vital Brasil Avenue, 05503-900, São Paulo, Brazil
| | - Hugo Aguirre Armelin
- Laboratório Especial de Ciclo Celular, Center of Toxins, Immune Response and Cell Signaling (CeTICS), Butantan Institute, 1500, Vital Brasil Avenue, 05503-900, São Paulo, Brazil
| | - Maria Carolina Elias
- Laboratório Especial de Ciclo Celular, Center of Toxins, Immune Response and Cell Signaling (CeTICS), Butantan Institute, 1500, Vital Brasil Avenue, 05503-900, São Paulo, Brazil
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17
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Uzcanga G, Lara E, Gutiérrez F, Beaty D, Beske T, Teran R, Navarro JC, Pasero P, Benítez W, Poveda A. Nuclear DNA replication and repair in parasites of the genus Leishmania: Exploiting differences to develop innovative therapeutic approaches. Crit Rev Microbiol 2016; 43:156-177. [PMID: 27960617 DOI: 10.1080/1040841x.2016.1188758] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Leishmaniasis is a common tropical disease that affects mainly poor people in underdeveloped and developing countries. This largely neglected infection is caused by Leishmania spp, a parasite from the Trypanosomatidae family. This parasitic disease has different clinical manifestations, ranging from localized cutaneous to more harmful visceral forms. The main limitations of the current treatments are their high cost, toxicity, lack of specificity, and long duration. Efforts to improve treatments are necessary to deal with this infectious disease. Many approved drugs to combat diseases as diverse as cancer, bacterial, or viral infections take advantage of specific features of the causing agent or of the disease. Recent evidence indicates that the specific characteristics of the Trypanosomatidae replication and repair machineries could be used as possible targets for the development of new treatments. Here, we review in detail the molecular mechanisms of DNA replication and repair regulation in trypanosomatids of the genus Leishmania and the drugs that could be useful against this disease.
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Affiliation(s)
- Graciela Uzcanga
- a Centro Internacional de Zoonosis, Facultad de Ciencias Químicas, Facultad de Medicina Veterinaria , Universidad Central del Ecuador , Quito , Ecuador.,b Programa Prometeo , SENESCYT, Whymper E7-37 y Alpallana, Quito , Ecuador.,c Facultad de Ciencias Naturales y Ambientales, Universidad Internacional SEK Calle Alberto Einstein sn y 5ta transversal , Quito , Ecuador.,d Fundación Instituto de Estudios Avanzados-IDEA , Caracas , Venezuela
| | - Eliana Lara
- a Centro Internacional de Zoonosis, Facultad de Ciencias Químicas, Facultad de Medicina Veterinaria , Universidad Central del Ecuador , Quito , Ecuador.,e Institute of Human Genetics , CNRS UPR 1142, 141 rue de la Cardonille, Equipe Labellisée Ligue Contre le Cancer , Montpellier cedex 5 , France
| | - Fernanda Gutiérrez
- a Centro Internacional de Zoonosis, Facultad de Ciencias Químicas, Facultad de Medicina Veterinaria , Universidad Central del Ecuador , Quito , Ecuador
| | - Doyle Beaty
- a Centro Internacional de Zoonosis, Facultad de Ciencias Químicas, Facultad de Medicina Veterinaria , Universidad Central del Ecuador , Quito , Ecuador
| | - Timo Beske
- a Centro Internacional de Zoonosis, Facultad de Ciencias Químicas, Facultad de Medicina Veterinaria , Universidad Central del Ecuador , Quito , Ecuador
| | - Rommy Teran
- a Centro Internacional de Zoonosis, Facultad de Ciencias Químicas, Facultad de Medicina Veterinaria , Universidad Central del Ecuador , Quito , Ecuador
| | - Juan-Carlos Navarro
- a Centro Internacional de Zoonosis, Facultad de Ciencias Químicas, Facultad de Medicina Veterinaria , Universidad Central del Ecuador , Quito , Ecuador.,f Universidad Central de Venezuela, Instituto de Zoología y Ecología Tropical , Caracas , Venezuela.,g Facultad de Ciencias Naturales y Ambientales, Universidad Internacional SEK, Calle Alberto Einstein sn y 5ta transversal , Quito , Ecuador
| | - Philippe Pasero
- e Institute of Human Genetics , CNRS UPR 1142, 141 rue de la Cardonille, Equipe Labellisée Ligue Contre le Cancer , Montpellier cedex 5 , France
| | - Washington Benítez
- a Centro Internacional de Zoonosis, Facultad de Ciencias Químicas, Facultad de Medicina Veterinaria , Universidad Central del Ecuador , Quito , Ecuador
| | - Ana Poveda
- a Centro Internacional de Zoonosis, Facultad de Ciencias Químicas, Facultad de Medicina Veterinaria , Universidad Central del Ecuador , Quito , Ecuador
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18
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Liao S, Hu H, Wang T, Tu X, Li Z. The Protein Neddylation Pathway in Trypanosoma brucei: FUNCTIONAL CHARACTERIZATION AND SUBSTRATE IDENTIFICATION. J Biol Chem 2016; 292:1081-1091. [PMID: 27956554 DOI: 10.1074/jbc.m116.766741] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 11/28/2016] [Indexed: 11/06/2022] Open
Abstract
Protein posttranslational modifications such as neddylation play crucial roles in regulating protein function. Only a few neddylated substrates have been validated to date, and the role of neddylation remains poorly understood. Here, using Trypanosoma brucei as the model organism, we investigated the function and substrates of TbNedd8. TbNedd8 is distributed throughout the cytosol but enriched in the nucleus and the flagellum. Depletion of TbNedd8 by RNAi abolished global protein ubiquitination, caused DNA re-replication in postmitotic cells, impaired spindle assembly, and compromised the flagellum attachment zone filament, leading to flagellum detachment. Through affinity purification and mass spectrometry, we identified 70 TbNedd8-conjugated and -associated proteins, including known Nedd8-conjugated and -associated proteins, putative TbNedd8 conjugation system enzymes, proteins of diverse biological functions, and proteins of unknown function. Finally, we validated six Cullins as bona fide TbNedd8 substrates and identified the TbNedd8 conjugation site in three Cullins. This work lays the foundation for understanding the roles of protein neddylation in this early divergent parasitic protozoan.
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Affiliation(s)
- Shanhui Liao
- From the Hefei National Laboratory for Physical Sciences at Microscale, School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China and.,the Department of Microbiology and Molecular Genetics, McGovern Medical School, University of Texas Health Science Center, Houston, Texas 77030
| | - Huiqing Hu
- the Department of Microbiology and Molecular Genetics, McGovern Medical School, University of Texas Health Science Center, Houston, Texas 77030
| | - Tao Wang
- the Department of Microbiology and Molecular Genetics, McGovern Medical School, University of Texas Health Science Center, Houston, Texas 77030
| | - Xiaoming Tu
- From the Hefei National Laboratory for Physical Sciences at Microscale, School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China and
| | - Ziyin Li
- the Department of Microbiology and Molecular Genetics, McGovern Medical School, University of Texas Health Science Center, Houston, Texas 77030
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19
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Marques CA, Tiengwe C, Lemgruber L, Damasceno JD, Scott A, Paape D, Marcello L, McCulloch R. Diverged composition and regulation of the Trypanosoma brucei origin recognition complex that mediates DNA replication initiation. Nucleic Acids Res 2016; 44:4763-84. [PMID: 26951375 PMCID: PMC4889932 DOI: 10.1093/nar/gkw147] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Accepted: 03/01/2016] [Indexed: 01/14/2023] Open
Abstract
Initiation of DNA replication depends upon recognition of genomic sites, termed origins, by AAA+ ATPases. In prokaryotes a single factor binds each origin, whereas in eukaryotes this role is played by a six-protein origin recognition complex (ORC). Why eukaryotes evolved a multisubunit initiator, and the roles of each component, remains unclear. In Trypanosoma brucei, an ancient unicellular eukaryote, only one ORC-related initiator, TbORC1/CDC6, has been identified by sequence homology. Here we show that three TbORC1/CDC6-interacting factors also act in T. brucei nuclear DNA replication and demonstrate that TbORC1/CDC6 interacts in a high molecular complex in which a diverged Orc4 homologue and one replicative helicase subunit can also be found. Analysing the subcellular localization of four TbORC1/CDC6-interacting factors during the cell cycle reveals that one factor, TbORC1B, is not a static constituent of ORC but displays S-phase restricted nuclear localization and expression, suggesting it positively regulates replication. This work shows that ORC architecture and regulation are diverged features of DNA replication initiation in T. brucei, providing new insight into this key stage of eukaryotic genome copying.
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Affiliation(s)
- Catarina A Marques
- The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK
| | - Calvin Tiengwe
- The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK
| | - Leandro Lemgruber
- The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK
| | - Jeziel D Damasceno
- The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK
| | - Alan Scott
- The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK
| | - Daniel Paape
- The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK
| | - Lucio Marcello
- The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK
| | - Richard McCulloch
- The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK
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20
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Valenciano AL, Ramsey AC, Mackey ZB. Deviating the level of proliferating cell nuclear antigen in Trypanosoma brucei elicits distinct mechanisms for inhibiting proliferation and cell cycle progression. Cell Cycle 2015; 14:674-88. [PMID: 25701409 DOI: 10.4161/15384101.2014.987611] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The DNA replication machinery is spatially and temporally coordinated in all cells to reproduce a single exact copy of the genome per division, but its regulation in the protozoan parasite Trypanosoma brucei is not well characterized. We characterized the effects of altering the levels of proliferating cell nuclear antigen, a key component of the DNA replication machinery, in bloodstream form T. brucei. This study demonstrated that tight regulation of TbPCNA levels was critical for normal proliferation and DNA replication in the parasite. Depleting TbPCNA mRNA reduced proliferation, severely diminished DNA replication, arrested the synthesis of new DNA and caused the parasites to accumulated in G2/M. Attenuating the parasite by downregulating TbPCNA caused it to become hypersensitive to hydroxyurea. Overexpressing TbPCNA in T. brucei arrested proliferation, inhibited DNA replication and prevented the parasite from exiting G2/M. These results indicate that distinct mechanisms of cell cycle arrest are associated with upregulating or downregulating TbPCNA. The findings of this study validate deregulating intra-parasite levels of TbPCNA as a potential strategy for therapeutically exploiting this target in bloodstream form T. brucei.
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Key Words
- CDK, cyclin dependent kinase
- Cd, Cluster of differentiation
- DAPI, 4′, 6-diamidino-2-phenylindole
- DNA replication
- EdU, 5-Ethynyl-2′deoxyuridine
- GINS, Go, Ichi, Nii, complex
- Gadd, growth arrest and DNA-damage
- H2O2, hydrogen peroxide
- HU, hydroxyurea
- Hs, Homo sapiens
- Mcm, mini-chromosome maintenance proteins
- MyD, myeloid differentiation primary response gene
- Orc, origin recognition complex
- PCNA, proliferating cell nuclear antigen
- RT-PCR, reverse transcriptase-polymerase chain reaction
- Sc, Saccharomyces cerevisiae
- Sp, Schizosaccharomyces pombe
- Tb, Trypanosoma brucei
- attenuate
- chemosensitize
- hydroxyurea
- proliferation
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Affiliation(s)
- Ana L Valenciano
- a Department of Biochemistry ; Virginia Polytechnic Institute and State University ; Blacksburg , VA USA
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21
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Calderano SG, Drosopoulos WC, Quaresma MM, Marques CA, Kosiyatrakul S, McCulloch R, Schildkraut CL, Elias MC. Single molecule analysis of Trypanosoma brucei DNA replication dynamics. Nucleic Acids Res 2015; 43:2655-65. [PMID: 25690894 PMCID: PMC4357695 DOI: 10.1093/nar/gku1389] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Eukaryotic genome duplication relies on origins of replication, distributed over multiple chromosomes, to initiate DNA replication. A recent genome-wide analysis of Trypanosoma brucei, the etiological agent of sleeping sickness, localized its replication origins to the boundaries of multigenic transcription units. To better understand genomic replication in this organism, we examined replication by single molecule analysis of replicated DNA. We determined the average speed of replication forks of procyclic and bloodstream form cells and we found that T. brucei DNA replication rate is similar to rates seen in other eukaryotes. We also analyzed the replication dynamics of a central region of chromosome 1 in procyclic forms. We present evidence for replication terminating within the central part of the chromosome and thus emanating from both sides, suggesting a previously unmapped origin toward the 5′ extremity of chromosome 1. Also, termination is not at a fixed location in chromosome 1, but is rather variable. Importantly, we found a replication origin located near an ORC1/CDC6 binding site that is detected after replicative stress induced by hydroxyurea treatment, suggesting it may be a dormant origin activated in response to replicative stress. Collectively, our findings support the existence of more replication origins in T. brucei than previously appreciated.
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Affiliation(s)
- Simone Guedes Calderano
- Laboratório Especial de Ciclo Celular, Instituto Butantan, São Paulo, SP 05503-900, Brasil Center of Toxins, Immune Response and Cell Signaling - CeTICS, Instituto Butantan, São Paulo, SP 05503-900, Brasil
| | - William C Drosopoulos
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Marina Mônaco Quaresma
- Laboratório Especial de Ciclo Celular, Instituto Butantan, São Paulo, SP 05503-900, Brasil Center of Toxins, Immune Response and Cell Signaling - CeTICS, Instituto Butantan, São Paulo, SP 05503-900, Brasil
| | - Catarina A Marques
- The Wellcome Trust Centre for Molecular Parasitology, College of Medical, Veterinary and Life Sciences, Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, G128TA, UK
| | | | - Richard McCulloch
- The Wellcome Trust Centre for Molecular Parasitology, College of Medical, Veterinary and Life Sciences, Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, G128TA, UK
| | - Carl L Schildkraut
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Maria Carolina Elias
- Laboratório Especial de Ciclo Celular, Instituto Butantan, São Paulo, SP 05503-900, Brasil Center of Toxins, Immune Response and Cell Signaling - CeTICS, Instituto Butantan, São Paulo, SP 05503-900, Brasil
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22
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Centrin3 in trypanosomes maintains the stability of a flagellar inner-arm dynein for cell motility. Nat Commun 2014; 5:4060. [PMID: 24892844 PMCID: PMC4076704 DOI: 10.1038/ncomms5060] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Accepted: 05/06/2014] [Indexed: 11/20/2022] Open
Abstract
Centrin is a conserved component of centrioles in animals and basal bodies in flagellated organisms. It also associates with axonemal inner-arm dyneins and regulates cell motility, but the underlying mechanism remains elusive. In Trypanosoma brucei, three of the five centrins associate with the flagellar basal body, but no centrin has been found to regulate flagellar motility. Here we show that TbCentrin3 is a flagellar protein and knockdown of TbCentrin3 compromises cell motility. Tandem affinity purification followed by mass spectrometry identifies an inner-arm dynein, TbIAD5-1, as the TbCentrin3 partner, and knockdown of TbIAD5-1 causes similar cell motility defect. Further, we demonstrate the interdependence of TbCentrin3 and TbIAD5-1 for maintaining a stable complex in the flagellar axoneme. Together, these results identify the essential role of TbCentrin3 in cell motility by maintaining the stability of an inner-arm dynein in the flagellum, which may be shared by all the centrin-containing flagellated and ciliated organisms.
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23
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Calderano S, Godoy P, Soares D, Sant’Anna OA, Schenkman S, Elias MC. ORC1/CDC6 and MCM7 distinct associate with chromatin through Trypanosoma cruzi life cycle. Mol Biochem Parasitol 2014; 193:110-3. [DOI: 10.1016/j.molbiopara.2014.03.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2013] [Revised: 02/17/2014] [Accepted: 03/17/2014] [Indexed: 11/24/2022]
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24
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Hu H, Yu Z, Liu Y, Wang T, Wei Y, Li Z. The Aurora B kinase in Trypanosoma brucei undergoes post-translational modifications and is targeted to various subcellular locations through binding to TbCPC1. Mol Microbiol 2013; 91:256-74. [PMID: 24224936 DOI: 10.1111/mmi.12458] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/10/2013] [Indexed: 11/30/2022]
Abstract
The chromosomal passenger complex (CPC) in animals, consisting of Aurora B kinase and three evolutionarily conserved proteins, plays crucial roles in mitosis and cytokinesis. However, Trypanosoma brucei expresses an unusual CPC consisting of an Aurora-like kinase, TbAUK1, and two kinetoplastid-specific proteins, TbCPC1 and TbCPC2. Despite their essential functions, little is known about the regulation of TbAUK1 and the roles of TbCPC1 and TbCPC2. Here, we investigate the effect of post-translational modification on the activity and spatiotemporal control of TbAUK1, and demonstrate that phosphorylation of two conserved threonine residues in the activation loop of the kinase domain contributes to TbAUK1 activation and function. TbAUK1 is SUMOylated in vivo, and mutation of the SUMO-conjugation site compromises TbAUK1 function. Degradation of TbAUK1 requires two destruction boxes and is mediated by the anaphase-promoting complex/cyclosome (APC/C), whereas degradation of TbCPC1 and TbCPC2 is not dependent on the predicted destruction boxes and is APC/C-independent. Moreover, we determine the domains in CPC subunits that mediate the pairwise interactions, and show that disruption of the interaction impairs the localization of TbAUK1 and TbCPC2 but not TbCPC1. Our results demonstrate the requirement of post-translational modifications for TbAUK1 function and a crucial role of TbCPC1 in mediating TbAUK1 localization.
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Affiliation(s)
- Huiqing Hu
- Department of Microbiology and Molecular Genetics, University of Texas Medical School at Houston, Houston, TX, 77030, USA
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Tiengwe C, Marques CA, McCulloch R. Nuclear DNA replication initiation in kinetoplastid parasites: new insights into an ancient process. Trends Parasitol 2013; 30:27-36. [PMID: 24287149 DOI: 10.1016/j.pt.2013.10.009] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Revised: 10/28/2013] [Accepted: 10/30/2013] [Indexed: 12/23/2022]
Abstract
Nuclear DNA replication is, arguably, the central cellular process in eukaryotes, because it drives propagation of life and intersects with many other genome reactions. Perhaps surprisingly, our understanding of nuclear DNA replication in kinetoplastids was limited until a clutch of studies emerged recently, revealing new insight into both the machinery and genome-wide coordination of the reaction. Here, we discuss how these studies suggest that the earliest acting components of the kinetoplastid nuclear DNA replication machinery - the factors that demarcate sites of the replication initiation, termed origins - are diverged from model eukaryotes. In addition, we discuss how origin usage and replication dynamics relate to the highly unusual organisation of transcription in the genome of Trypanosoma brucei.
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Affiliation(s)
- Calvin Tiengwe
- The University of Glasgow, Wellcome Trust Centre for Molecular Parasitology and Institute of Infection, Immunity and Inflammation, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK; The Johns Hopkins University School of Medicine, Department of Cell Biology, Baltimore, MD, USA
| | - Catarina A Marques
- The University of Glasgow, Wellcome Trust Centre for Molecular Parasitology and Institute of Infection, Immunity and Inflammation, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK
| | - Richard McCulloch
- The University of Glasgow, Wellcome Trust Centre for Molecular Parasitology and Institute of Infection, Immunity and Inflammation, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK.
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Distinct roles of a mitogen-activated protein kinase in cytokinesis between different life cycle forms of Trypanosoma brucei. EUKARYOTIC CELL 2013; 13:110-8. [PMID: 24213350 DOI: 10.1128/ec.00258-13] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Mitogen-activated protein kinase (MAPK) modules are evolutionarily conserved signaling cascades that function in response to the environment and play crucial roles in intracellular signal transduction in eukaryotes. The involvement of a MAP kinase in regulating cytokinesis in yeast, animals, and plants has been reported, but the requirement for a MAP kinase for cytokinesis in the early-branching protozoa is not documented. Here, we show that a MAP kinase homolog (TbMAPK6) from Trypanosoma brucei plays distinct roles in cytokinesis in two life cycle forms of T. brucei. TbMAPK6 is distributed throughout the cytosol in the procyclic form but is localized in both the cytosol and the nucleus in the bloodstream form. RNA interference (RNAi) of TbMAPK6 results in moderate growth inhibition in the procyclic form but severe growth defects and rapid cell death in the bloodstream form. Moreover, TbMAPK6 appears to be implicated in furrow ingression and cytokinesis completion in the procyclic form but is essential for cytokinesis initiation in the bloodstream form. Despite the distinct defects in cytokinesis in the two forms, RNAi of TbMAPK6 also caused defective basal body duplication/segregation in a small cell population in both life cycle forms. Altogether, our results demonstrate the involvement of the TbMAPK6-mediated pathway in regulating cytokinesis in trypanosomes and suggest distinct roles of TbMAPK6 in cytokinesis between different life cycle stages of T. brucei.
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Lott K, Li J, Fisk JC, Wang H, Aletta JM, Qu J, Read LK. Global proteomic analysis in trypanosomes reveals unique proteins and conserved cellular processes impacted by arginine methylation. J Proteomics 2013; 91:210-25. [PMID: 23872088 PMCID: PMC3935770 DOI: 10.1016/j.jprot.2013.07.010] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Revised: 06/26/2013] [Accepted: 07/07/2013] [Indexed: 12/14/2022]
Abstract
Arginine methylation is a common posttranslational modification with reported functions in transcription, RNA processing and translation, and DNA repair. Trypanosomes encode five protein arginine methyltransferases, suggesting that arginine methylation exerts widespread impacts on the biology of these organisms. Here, we performed a global proteomic analysis of Trypanosoma brucei to identify arginine methylated proteins and their sites of modification. Using an approach entailing two-dimensional chromatographic separation and alternating electron transfer dissociation and collision induced dissociation, we identified 1332 methylarginines in 676 proteins. The resulting data set represents the largest compilation of arginine methylated proteins in any organism to date. Functional classification revealed numerous arginine methylated proteins involved in flagellar function, RNA metabolism, DNA replication and repair, and intracellular protein trafficking. Thus, arginine methylation has the potential to impact aspects of T. brucei gene expression, cell biology, and pathogenesis. Interestingly, pathways with known methylated proteins in higher eukaryotes were identified in this study, but often different components of the pathway were methylated in trypanosomes. Methylarginines were often identified in glycine rich contexts, although exceptions to this rule were detected. Collectively, these data inform on a multitude of aspects of trypanosome biology and serve as a guide for the identification of homologous arginine methylated proteins in higher eukaryotes. BIOLOGICAL SIGNIFICANCE T. brucei is a protozoan parasite that causes lethal African sleeping sickness in humans and nagana in livestock, thereby imposing a significant medical and economic burden on sub-Saharan Africa. The parasite encounters very different environments as it cycles between mammalian and insect hosts, and must exert cellular responses to these varying milieus. One mechanism by which all cells respond to changing environments is through posttranslational modification of proteins. Arginine methylation is one such modification that can dramatically impact protein-protein and protein-nucleic acid interactions and subcellular localization of proteins. To define the breadth of arginine methylation in trypanosomes and identify target proteins, we performed a global proteomic analysis of arginine methylated proteins in insect stage T. brucei. We identified 1332 methylarginines in 676 proteins, generating the largest compilation of methylarginine containing proteins in any organism to date. Numerous arginine methylated proteins function in RNA and DNA related processes, suggesting this modification can impact T. brucei genome integrity and gene regulation at numerous points. Other processes that appear to be strongly influenced by arginine methylation are intracellular protein trafficking, signaling, protein folding and degradation, and flagellar function. The widespread nature of arginine methylation in trypanosomes highlights its potential to greatly affect parasite biology and pathogenesis.
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Affiliation(s)
- Kaylen Lott
- Department of Microbiology and Immunology, School of Medicine and Biomedical Sciences, University at Buffalo, State University of New York, Buffalo, New York, United States of America
| | - Jun Li
- Department of Pharmaceutical Sciences, University at Buffalo, Buffalo, NY, United States of America
| | - John C. Fisk
- Department of Microbiology and Immunology, School of Medicine and Biomedical Sciences, University at Buffalo, State University of New York, Buffalo, New York, United States of America
| | - Hao Wang
- Department of Pharmaceutical Sciences, University at Buffalo, Buffalo, NY, United States of America
| | - John M. Aletta
- CH3 BioSystems, New York State Center of Excellence in Bioinformatics and Life Sciences, Buffalo, NY, United States of America
| | - Jun Qu
- Department of Pharmaceutical Sciences, University at Buffalo, Buffalo, NY, United States of America
| | - Laurie K. Read
- Department of Microbiology and Immunology, School of Medicine and Biomedical Sciences, University at Buffalo, State University of New York, Buffalo, New York, United States of America
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Wei Y, Hu H, Lun ZR, Li Z. The cooperative roles of two kinetoplastid-specific kinesins in cytokinesis and in maintaining cell morphology in bloodstream trypanosomes. PLoS One 2013; 8:e73869. [PMID: 24069240 PMCID: PMC3772034 DOI: 10.1371/journal.pone.0073869] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Accepted: 07/23/2013] [Indexed: 11/19/2022] Open
Abstract
The cytoskeleton of Trypanosoma brucei, a unicellular eukaryote and a parasitic protozoan, is defined by the subpellicular microtubule corset that is arranged underneath the plasma membrane. We recently identified two orphan kinesins, TbKIN-C and TbKIN-D, that cooperate to regulate the organization of the subpellicular microtubule corset and thereby maintain cell morphology in the procyclic form of T. brucei. In this report, we characterize the function of TbKIN-C and TbKIN-D in the bloodstream form of T. brucei and investigate their functional cooperation in both the bloodstream and procyclic forms. TbKIN-C and TbKIN-D form a tight complex in vivo in the bloodstream form. TbKIN-C is strongly enriched at the posterior tip of the cell, whereas TbKIN-D is distributed throughout the cell body at all cell cycle stages. RNAi of TbKIN-C or TbKIN-D in the bloodstream form inhibits cell proliferation and leads to cell death, due to cytokinesis defects. RNAi of TbKIN-C and TbKIN-D also results in defects in basal body segregation, but does not affect the synthesis and segregation of the flagellum and the flagellum attachment zone (FAZ) filament. Knockdown of TbKIN-C and TbKIN-D does not disrupt the organization of the subpellicular microtubule corset, but produces multinucleated cells with an enlarged flagellar pocket and misplaced flagella. Interestingly, depletion of TbKIN-C results in rapid degradation of TbKIN-D and, similarly, knockdown of TbKIN-C destabilizes TbKIN-D, suggesting that formation of TbKIN-C/TbKIN-D complex stabilizes both kinesins and is required for the two kinesins to execute their essential cellular functions. Altogether, our results demonstrate the essential role of the two kinesins in cell morphogenesis and cytokinesis in the bloodstream form and the requirement of heteromeric complex formation for maintaining the stability of the two kinesins.
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Affiliation(s)
- Ying Wei
- State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou, Guangdong, China
- Department of Microbiology and Molecular Genetics, University of Texas Medical School, Houston, Texas, United States of America
| | - Huiqing Hu
- Department of Microbiology and Molecular Genetics, University of Texas Medical School, Houston, Texas, United States of America
| | - Zhao-Rong Lun
- State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou, Guangdong, China
| | - Ziyin Li
- Department of Microbiology and Molecular Genetics, University of Texas Medical School, Houston, Texas, United States of America
- * E-mail:
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Liu Y, Hu H, Li Z. The cooperative roles of PHO80-like cyclins in regulating the G1/S transition and posterior cytoskeletal morphogenesis in Trypanosoma brucei. Mol Microbiol 2013; 90:130-46. [PMID: 23909752 DOI: 10.1111/mmi.12352] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/30/2013] [Indexed: 12/23/2022]
Abstract
Cyclins and cyclin-dependent kinases (CDKs) represent the fundamental, crucial regulators of the cell division cycle in eukaryotes. Trypanosoma brucei expresses a large number of cyclins and Cdc2-related kinases (CRKs). However, how these cyclins and CRKs cooperate to regulate cell cycle progression remains poorly understood. Here, we carry out directional yeast two-hybrid assays to identify the interactions between the 10 cyclins and the 11 CRKs and detect a total of 26 cyclin-CRK pairs, among which 20 pairs are new. Our current efforts are focused on four PHO80-like cyclins, CYC2, CYC4, CYC5 and CYC7, and their physical and functional interactions with CRK1. Silencing of the four cyclins and CRK1 leads to the increase of G1 cells and defective DNA replication, suggesting their important roles in promoting the G1/S transition. Additionally, CYC2-, CYC7- and CRK1-deficient cells possess an elongated posterior that is filled with newly assembled microtubules. Further, we show that the four cyclins display distinct subcellular localizations and half-lives, suggesting that they likely undergo distinct regulation. Altogether, our results demonstrate the involvement of four CRK1-associated cyclins, CYC2, CYC4, CYC5 and CYC7, in promoting the G1/S transition and the requirement of CYC2 and CYC7 in maintaining posterior cytoskeletal morphogenesis during the G1/S transition.
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Affiliation(s)
- Yi Liu
- Department of Microbiology and Molecular Genetics, University of Texas Medical School at Houston, Houston, TX, 77030, USA
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Abstract
ORC (origin recognition complex) serves as the initiator for the assembly of the pre-RC (pre-replication complex) and the subsequent DNA replication. Together with many of its non-replication functions, ORC is a pivotal regulator of various cellular processes. Notably, a number of reports connect ORC to numerous human diseases, including MGS (Meier-Gorlin syndrome), EBV (Epstein-Barr virus)-infected diseases, American trypanosomiasis and African trypanosomiasis. However, much of the underlying molecular mechanism remains unclear. In those genetic diseases, mutations in ORC alter its function and lead to the dysregulated phenotypes; whereas in some pathogen-induced symptoms, host ORC and archaeal-like ORC are exploited by these organisms to maintain their own genomes. In this review, I provide detailed examples of ORC-related human diseases, and summarize the current findings on how ORC is involved and/or dysregulated. I further discuss how these discoveries can be generalized as model systems, which can then be applied to elucidating other related diseases and revealing potential targets for developing effective therapies.
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Huang TH, Huo L, Wang YN, Xia W, Wei Y, Chang SS, Chang WC, Fang YF, Chen CT, Lang JY, Tu C, Wang Y, Hsu MC, Kuo HP, Ko HW, Shen J, Lee HH, Lee PC, Wu Y, Chen CH, Hung MC. Epidermal growth factor receptor potentiates MCM7-mediated DNA replication through tyrosine phosphorylation of Lyn kinase in human cancers. Cancer Cell 2013; 23:796-810. [PMID: 23764002 PMCID: PMC3703149 DOI: 10.1016/j.ccr.2013.04.027] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2012] [Revised: 11/17/2012] [Accepted: 04/26/2013] [Indexed: 12/14/2022]
Abstract
Epidermal growth factor receptor (EGFR) initiates a signaling cascade that leads to DNA synthesis and cell proliferation, but its role in regulating DNA replication licensing is unclear. Here, we show that activated EGFR phosphorylates the p56 isoform of Lyn, p56(Lyn), at Y32, which then phosphorylates MCM7, a licensing factor critical for DNA replication, at Y600 to increase its association with other minichromosome maintenance complex proteins, thereby promoting DNA synthesis complex assembly and cell proliferation. Both p56(Lyn) Y32 and MCM7 Y600 phosphorylation are enhanced in proliferating cells and correlated with poor survival of breast cancer patients. These results establish a signaling cascade in which EGFR enhances MCM7 phosphorylation and DNA replication through Lyn phosphorylation in human cancer cells.
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Affiliation(s)
- Tzu-Hsuan Huang
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
| | - Longfei Huo
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
| | - Ying-Nai Wang
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
- Center for Molecular Medicine and Graduate Institute of Cancer Biology, China Medical University, Taichung 404, Taiwan.
- Asia University, Taichung 413, Taiwan.
| | - Weiya Xia
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
| | - Yongkun Wei
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
| | - Shih-Shin Chang
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
- The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas 77030, USA.
| | - Wei-Chao Chang
- The Genomics Research Center, Academia Sinica, 128 Academia Road, Section 2, Nankang, Taipei 115, Taiwan.
- Center for Molecular Medicine and Graduate Institute of Cancer Biology, China Medical University, Taichung 404, Taiwan.
| | - Yueh-Fu Fang
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
| | - Chun-Te Chen
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
| | - Jing-Yu Lang
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
| | - Chun Tu
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
| | - Yan Wang
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
| | - Ming-Chuan Hsu
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
| | - Hsu-Ping Kuo
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
| | - How-Wen Ko
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
| | - Jia Shen
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
- The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas 77030, USA.
| | - Heng-Huan Lee
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
- The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas 77030, USA.
| | - Pei-Chih Lee
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
| | - Yun Wu
- Department of Pathology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
| | - Chung-Hsuan Chen
- The Genomics Research Center, Academia Sinica, 128 Academia Road, Section 2, Nankang, Taipei 115, Taiwan.
| | - Mien-Chie Hung
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
- The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas 77030, USA.
- Center for Molecular Medicine and Graduate Institute of Cancer Biology, China Medical University, Taichung 404, Taiwan.
- Asia University, Taichung 413, Taiwan.
- To whom correspondence should be addressed: Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Box 108, 1515 Holcombe Boulevard, Houston, TX 77030.
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Kim HS, Park SH, Günzl A, Cross GAM. MCM-BP is required for repression of life-cycle specific genes transcribed by RNA polymerase I in the mammalian infectious form of Trypanosoma brucei. PLoS One 2013; 8:e57001. [PMID: 23451133 PMCID: PMC3581582 DOI: 10.1371/journal.pone.0057001] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Accepted: 01/16/2013] [Indexed: 12/22/2022] Open
Abstract
Trypanosoma brucei variant surface glycoprotein (VSG) expression is a classic example of allelic exclusion. While the genome of T. brucei contains >2,000 VSG genes and VSG pseudogenes, only one allele is expressed at the surface of each infectious trypanosome and the others are repressed. Along with recombinatorial VSG switching, allelic exclusion provides a major host evasion mechanism for trypanosomes, a phenomenon known as antigenic variation. To extend our understanding of how trypanosomes escape host immunity by differential expression of VSGs, we attempted to identify genes that contribute to VSG silencing, by performing a loss-of-silencing screen in T. brucei using a transposon-mediated random insertional mutagenesis. One identified gene, which we initially named LOS1, encodes a T. brucei MCM-Binding Protein (TbMCM-BP). Here we show that TbMCM-BP is essential for viability of infectious bloodstream-form (BF) trypanosome and is required for proper cell-cycle progression. Tandem affinity purification of TbMCM-BP followed by mass spectrometry identified four subunits (MCM4-MCM7) of the T. brucei MCM complex, a replicative helicase, and MCM8, a subunit that is uniquely co-purified with TbMCM-BP. TbMCM-BP is required not only for repression of subtelomeric VSGs but also for silencing of life-cycle specific, insect-stage genes, procyclin and procyclin-associated genes (PAGs), that are normally repressed in BF trypanosomes and are transcribed by RNA polymerase I. Our study uncovers a functional link between chromosome maintenance and RNA pol I-mediated gene silencing in T. brucei.
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Affiliation(s)
- Hee-Sook Kim
- Laboratory of Molecular Parasitology, The Rockefeller University, New York, New York, United States of America.
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33
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Benmerzouga I, Concepción-Acevedo J, Kim HS, Vandoros AV, Cross GAM, Klingbeil MM, Li B. Trypanosoma brucei Orc1 is essential for nuclear DNA replication and affects both VSG silencing and VSG switching. Mol Microbiol 2012; 87:196-210. [PMID: 23216794 DOI: 10.1111/mmi.12093] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/06/2012] [Indexed: 11/29/2022]
Abstract
Binding of the Origin Recognition Complex (ORC) to replication origins is essential for initiation of DNA replication, but ORC has non-essential functions outside of DNA replication, including in heterochromatic gene silencing and telomere maintenance. Trypanosoma brucei, a protozoan parasite that causes human African trypanosomiasis, uses antigenic variation as a major virulence mechanism to evade the host's immune attack by expressing its major surface antigen, the Variant Surface Glycoprotein (VSG), in a monoallelic manner. An Orc1/Cdc6 homologue has been identified in T. brucei, but its role in DNA replication has not been directly confirmed and its potential involvement in VSG repression or switching has not been thoroughly investigated. In this study, we show that TbOrc1 is essential for nuclear DNA replication in mammalian-infectious bloodstream and tsetse procyclic forms (BF and PF). Depletion of TbOrc1 resulted in derepression of telomere-linked silent VSGs in both BF and PF, and increased VSG switching particularly through the in situ transcriptional switching mechanism. TbOrc1 associates with telomere repeats but appears to do so independently of two known T. brucei telomere proteins, TbRAP1 and TbTRF. We conclude that TbOrc1 has conserved functions in DNA replication and is also required to control telomere-linked VSG expression and VSG switching.
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Affiliation(s)
- Imaan Benmerzouga
- Center for Gene Regulation in Health & Disease, Department of Biological, Geological, and Environmental Sciences, Cleveland State University, Cleveland, OH 44115, USA
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Gassen A, Brechtefeld D, Schandry N, Arteaga-Salas JM, Israel L, Imhof A, Janzen CJ. DOT1A-dependent H3K76 methylation is required for replication regulation in Trypanosoma brucei. Nucleic Acids Res 2012; 40:10302-11. [PMID: 22941659 PMCID: PMC3488242 DOI: 10.1093/nar/gks801] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Cell-cycle progression requires careful regulation to ensure accurate propagation of genetic material to the daughter cells. Although many cell-cycle regulators are evolutionarily conserved in the protozoan parasite Trypanosoma brucei, novel regulatory mechanisms seem to have evolved. Here, we analyse the function of the histone methyltransferase DOT1A during cell-cycle progression. Over-expression of DOT1A generates a population of cells with aneuploid nuclei as well as enucleated cells. Detailed analysis shows that DOT1A over-expression causes continuous replication of the nuclear DNA. In contrast, depletion of DOT1A by RNAi abolishes replication but does not prevent karyokinesis. As histone H3K76 methylation has never been associated with replication control in eukaryotes before, we have discovered a novel function of DOT1 enzymes, which might not be unique to trypanosomes.
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Affiliation(s)
- Alwine Gassen
- Department of Biology I, University of Munich (LMU), Genetics, Großhaderner Str. 2-4, 82152 Martinsried, Germany
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35
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Gargantini PR, Lujan HD, Pereira CA. In silicoanalysis of trypanosomatids' helicases. FEMS Microbiol Lett 2012; 335:123-9. [DOI: 10.1111/j.1574-6968.2012.02644.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Revised: 07/13/2012] [Accepted: 07/23/2012] [Indexed: 01/08/2023] Open
Affiliation(s)
- Pablo R. Gargantini
- Laboratorio de Bioquímica y Biología Molecular, Facultad de Medicina; Universidad Católica de Córdoba; Córdoba; Argentina
| | - Hugo D. Lujan
- Laboratorio de Bioquímica y Biología Molecular, Facultad de Medicina; Universidad Católica de Córdoba; Córdoba; Argentina
| | - Claudio A. Pereira
- Laboratorio de Biología Molecular de Trypanosoma cruzi (LBMTC), Instituto de Investigaciones Médicas ‘Alfredo Lanari’; Universidad de Buenos Aires and CONICET; Buenos Aires; Argentina
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Abstract
The cell division cycle is tightly regulated by the activation and inactivation of a series of proteins that control the replication and segregation of organelles to the daughter cells. During the past decade, we have witnessed significant advances in our understanding of the cell cycle in Trypanosoma brucei and how the cycle is regulated by various regulatory proteins. However, many other regulators, especially those unique to trypanosomes, remain to be identified, and we are just beginning to delineate the signaling pathways that drive the transitions through different cell cycle stages, such as the G(1)/S transition, G(2)/M transition, and mitosis-cytokinesis transition. Trypanosomes appear to employ both evolutionarily conserved and trypanosome-specific molecules to regulate the various stages of its cell cycle, including DNA replication initiation, spindle assembly, chromosome segregation, and cytokinesis initiation and completion. Strikingly, trypanosomes lack some crucial regulators that are well conserved across evolution, such as Cdc6 and Cdt1, which are involved in DNA replication licensing, the spindle motor kinesin-5, which is required for spindle assembly, the central spindlin complex, which has been implicated in cytokinesis initiation, and the actomyosin contractile ring, which is located at the cleavage furrow. Conversely, trypanosomes possess certain regulators, such as cyclins, cyclin-dependent kinases, and mitotic centromere-associated kinesins, that are greatly expanded and likely play diverse cellular functions. Overall, trypanosomes apparently have integrated unique regulators into the evolutionarily conserved pathways to compensate for the absence of those conserved molecules and, additionally, have evolved certain cell cycle regulatory pathways that are either different from its human host or distinct between its own life cycle forms.
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Hu H, Hu L, Yu Z, Chasse AE, Chu F, Li Z. An orphan kinesin in trypanosomes cooperates with a kinetoplastid-specific kinesin to maintain cell morphology by regulating subpellicular microtubules. J Cell Sci 2012; 125:4126-36. [PMID: 22623724 DOI: 10.1242/jcs.106534] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Microtubules are a vital part of the cytoskeleton of eukaryotic cells and are involved in various cellular processes. The cytoskeleton of Trypanosoma brucei is characterized by an array of subpellicular microtubules and is essential for maintenance of cell shape and polarity, but little is known about the regulation of the assembly and organization of the subpellicular microtubule corset. Here, we report that the orphan kinesin TbKIN-D regulates the organization of subpellicular microtubules and is required for maintaining cell morphology. TbKIN-D possesses in vitro ATPase activity, associates with cytoskeletal microtubules and is distributed throughout the cytoskeleton at all cell cycle stages. RNAi of TbKIN-D disrupts the organization of the subpellicular microtubule corset and distorts cell morphology, resulting in round cells with an elongated posterior filled with newly assembled microtubules. Depletion of TbKIN-D also abolishes the segregation of organelles and cytoskeletal structures, suggesting that cellular morphogenesis is essential for proper organelle segregation. Moreover, TbKIN-D deficiency impairs the attachment of the new flagellum without compromising the formation of the flagellum attachment zone. Finally, we identified TbKIN-C, a kinetoplastid-specific kinesin known to regulate subpellicular microtubules and cell morphogenesis in T. brucei, as a partner of TbKIN-D. Further, we demonstrate that interaction between TbKIN-C and TbKIN-D requires the coiled-coil motifs in the C-termini of both proteins. Altogether, our results suggest that TbKIN-D cooperates with TbKIN-C to maintain cell morphology by regulating the organization of the subpellicular microtubule corset.
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Affiliation(s)
- Huiqing Hu
- Department of Microbiology and Molecular Genetics, University of Texas Medical School, Houston, TX 77030, USA
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Tiengwe C, Marcello L, Farr H, Gadelha C, Burchmore R, Barry JD, Bell SD, McCulloch R. Identification of ORC1/CDC6-interacting factors in Trypanosoma brucei reveals critical features of origin recognition complex architecture. PLoS One 2012; 7:e32674. [PMID: 22412905 PMCID: PMC3297607 DOI: 10.1371/journal.pone.0032674] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Accepted: 02/02/2012] [Indexed: 12/13/2022] Open
Abstract
DNA Replication initiates by formation of a pre-replication complex on sequences termed origins. In eukaryotes, the pre-replication complex is composed of the Origin Recognition Complex (ORC), Cdc6 and the MCM replicative helicase in conjunction with Cdt1. Eukaryotic ORC is considered to be composed of six subunits, named Orc1–6, and monomeric Cdc6 is closely related in sequence to Orc1. However, ORC has been little explored in protists, and only a single ORC protein, related to both Orc1 and Cdc6, has been shown to act in DNA replication in Trypanosoma brucei. Here we identify three highly diverged putative T. brucei ORC components that interact with ORC1/CDC6 and contribute to cell division. Two of these factors are so diverged that we cannot determine if they are eukaryotic ORC subunit orthologues, or are parasite-specific replication factors. The other we show to be a highly diverged Orc4 orthologue, demonstrating that this is one of the most widely conserved ORC subunits in protists and revealing it to be a key element of eukaryotic ORC architecture. Additionally, we have examined interactions amongst the T. brucei MCM subunits and show that this has the conventional eukaryotic heterohexameric structure, suggesting that divergence in the T. brucei replication machinery is limited to the earliest steps in origin licensing.
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Affiliation(s)
- Calvin Tiengwe
- The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Lucio Marcello
- The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Helen Farr
- Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom
| | - Catarina Gadelha
- Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom
| | - Richard Burchmore
- Sir Henry Wellcome Functional Genomics Facility, Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - J. David Barry
- The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Stephen D. Bell
- Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom
| | - Richard McCulloch
- The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
- * E-mail:
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Kaufmann D, Gassen A, Maiser A, Leonhardt H, Janzen CJ. Regulation and spatial organization of PCNA in Trypanosoma brucei. Biochem Biophys Res Commun 2012; 419:698-702. [PMID: 22387477 DOI: 10.1016/j.bbrc.2012.02.082] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Accepted: 02/14/2012] [Indexed: 11/15/2022]
Abstract
As in most eukaryotic cells, replication is regulated by a conserved group of proteins in the early-diverged parasite Trypanosoma brucei. 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 T. brucei (TbPCNA) to establish a spatial and temporal marker for replication. Interestingly, PCNA distribution and regulation is different compared to the closely related parasites Trypanosoma cruzi and Leishmania donovani. TbPCNA foci are clearly detectable during S phase of the cell cycle but in contrast to T. cruzi they are not preferentially located at the nuclear periphery. Furthermore, PCNA seems to be degraded when cells enter G2 phase in T. brucei suggesting different modes of replication regulation or functions of PCNA in these closely related eukaryotes.
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Affiliation(s)
- Doris Kaufmann
- University of Munich (LMU), Department Biology I, Genetics, Großhaderner Str. 2-4, 82152 Martinsried, Germany
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Hu L, Hu H, Li Z. A kinetoplastid-specific kinesin is required for cytokinesis and for maintenance of cell morphology in Trypanosoma brucei. Mol Microbiol 2012; 83:565-78. [PMID: 22168367 DOI: 10.1111/j.1365-2958.2011.07951.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Kinesins are motor-based transport proteins that play diverse roles in various cellular processes. The trypanosome genome lacks the homologues of many conserved mitotic kinesins, but encodes a number of trypanosome-specific kinesins with unknown function. Here, we report the biochemical and functional characterization of TbKIN-C, a trypanosome-specific kinesin, which was initially identified through an RNAi screen for cytokinesis genes in T. brucei. TbKIN-C possesses in vitro ATPase activity and associates with cytoskeletal tubulin microtubules in vivo. It is distributed throughout the cytoskeleton with a focal enrichment at the posterior end of the cell during early cell cycle stages. RNAi of TbKIN-C resulted in distorted cell shape with an elongated posterior filled with tyrosinated tubulin microtubules. Silencing of TbKIN-C impaired the segregation of organelles and cytoskeletal structures and led to detachment of the new flagellum and a small portion of the cytoplasm. We also show that RNAi of TbKIN-C compromised cytokinesis and abolished the trans-localization of TbCPC1, a subunit of the chromosomal passenger complex, from the central spindle to the initiation site of cytokinesis. Our results suggest an essential role of TbKIN-C in maintaining cell morphology, likely through regulating microtubule dynamics at the posterior end of the cell.
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Affiliation(s)
- Liu Hu
- Department of Microbiology & Molecular Genetics, University of Texas Medical School at Houston, TX 77030, USA
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Aves SJ, Liu Y, Richards TA. Evolutionary diversification of eukaryotic DNA replication machinery. Subcell Biochem 2012; 62:19-35. [PMID: 22918578 DOI: 10.1007/978-94-007-4572-8_2] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
DNA replication research to date has focused on model organisms such as the vertebrate Xenopus laevis and the yeast species Saccharomyces cerevisiae and Schizosaccharomyces pombe. However, animals and fungi both belong to the Opisthokonta, one of about six eukaryotic phylogenetic 'supergroups', and therefore represent only a fraction of eukaryotic diversity. To explore evolutionary diversification of the eukaryotic DNA replication machinery a bioinformatic approach was used to investigate the presence or absence of yeast/animal replisome components in other eukaryotic taxa. A comparative genomic survey was undertaken of 59 DNA replication proteins in a diverse range of 36 eukaryotes from all six supergroups. Twenty-three proteins including Mcm2-7, Cdc45, RPA1, primase, some DNA polymerase subunits, RFC1-5, PCNA and Fen1 are present in all species examined. A further 20 proteins are present in all six eukaryotic supergroups, although not necessarily in every species: with the exception of RNase H2B and the fork protection complex component Timeless/Tof1, all of these are members of anciently derived paralogous families such as ORC, MCM, GINS or RPA. Together these form a set of 43 proteins that must have been present in the last common eukaryotic ancestor (LCEA). This minimal LCEA replisome is significantly more complex than the related replisome in Archaea, indicating evolutionary events including duplications of DNA replication genes in the LCEA lineage which parallel the early evolution of other complex eukaryotic cellular features.
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Affiliation(s)
- Stephen J Aves
- Biosciences, College of Life and Environmental Sciences, University of Exeter, Geoffrey Pope Building, Stocker Road, Exeter, EX4 4QD, UK,
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Abstract
High-fidelity chromosomal DNA replication is vital for maintaining the integrity of the genetic material in all forms of cellular life. In eukaryotic cells, around 40-50 distinct conserved polypeptides are essential for chromosome replication, the majority of which are themselves component parts of a series of elaborate molecular machines that comprise the replication apparatus or replisome. How these complexes are assembled, what structures they adopt, how they perform their functions, and how those functions are regulated, are key questions for understanding how genome duplication occurs. Here I present a brief overview of current knowledge of the composition of the replisome and the dynamic molecular events that underlie chromosomal DNA replication in eukaryotic cells.
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