TY  - THES
A1  - Reis, Helena
T1  - Characterization of telomere protein complexes in Trypanosoma brucei
T1  - Charakterisierung von telomerischen Proteinkomplexen in Trypanosoma brucei
N2  - African trypanosomiasis is a disease endemic to sub-Saharan Africa. It affects humans as well as wild and domestic animals. The human form of the disease is known as sleeping sickness and the animal form as nagana, which are usually fatal if left untreated. The cause of African trypanosomiasis is the unicellular parasite Trypanosoma brucei. During its life cycle, Trypanosoma brucei shuttles between a mammalian host and the tsetse fly vector. In the mammalian host the parasite multiplies as bloodstream form (BSF) extracellularly in the bloodstream or the lymphatic system. Survival of BSF parasites relies on immune evasion by antigenic variation of surface proteins because its extracellular lifestyle leads to direct exposure to immune responses. At any given time each BSF cell expresses a single type of variant surface glycoprotein (VSG) on its surface from a large repertoire. The active VSG is transcribed from one of 15 specialized subtelomeric domains, termed bloodstream expression sites (BESs). The remaining 14 BESs are silenced. This monoallelic expression and periodic switching of the expressed VSG enables to escape the immune response and to establish a persistent infection in the mammalian host. During developmental differentiation from BSF to the insect vector-resident procyclic form (PCF), the active BES is transcriptionally silenced to stop VSG transcription. Thus, all 15 BESs are inactive in the PCF cells as surface protein expression is developmentally regulated. 
Previous reports have shown that the telomere complex components TbTRF, TbRAP1 and TbTIF2 are involved in VSG transcriptional regulation. However, the precise nature of their contribution remains unclear. In addition, no information is available about the role of telomeres in the initiation and regulation of developmental BES silencing. To gain insights into the regulatory mechanisms of telomeres on VSG transcription and developmental repression it is therefore essential to identify the complete composition of the trypanosome telomere complex.
To this end, we used two complementary biochemical approaches and quantitative label-free interactomics to determine the composition of telomere protein complexes in T. brucei. Firstly, using a telomeric pull-down assay we found 17 potential telomere-binding proteins including the known telomere-binding proteins TbTRF and TbTIF2. Secondly, by performing a co-immunoprecipitation experiment to elucidate TbTRF interactions we co-purified five proteins. All of these five proteins were also enriched with telomeric DNA in the pull-down assay. 
To validate these data, I characterized one of the proteins found in both experiments (TelBP1). In BSF cells, TelBP1 co-localizes with TbTRF and interacts with already described telomere-binding proteins such as TbTRF, TbTIF2 and TbRAP1 indicating that TelBP1 is a novel component of the telomere complex in trypanosomes. Interestingly, protein interaction studies in PCF cells suggested a different telomere complex composition compared to BSF cells. In contrast to known members of the telomere complex, TelBP1 is dispensable for cell viability indicating that its function might be uncoupled from the known telomere-binding proteins. Overexpression of TelBP1 had also no effect on cell viability, but led to the discovery of two additional shorter isoforms of TelBP1. However, their source and function remained elusive. 
Although TelBP1 is not essential for cell viability, western blot analysis revealed a 4-fold upregulation of TelBP1 in the BSF stage compared to the PCF stage supporting the concept of a dynamic telomere complex composition. We observed that TelBP1 influences the kinetics of transcriptional BES silencing during developmental transition from BSF to PCF. Deletion of TelBP1 caused faster BES silencing compared to wild-type parasites. 
Taken together, TelBP1 function illustrates that developmental BES silencing is a fine-tuned process, which involves stage-specific changes in telomere complex formation.
N2  - Afrikanische Trypanosomiasis ist eine Krankheit, die in Afrika südlich der Sahara endemisch vorkommt und sowohl Menschen als auch Wild- und Haustiere betrifft. Die menschliche Form der Krankheit ist als Schlafkrankheit und die Tierform als Nagana bekannt. Ohne Behandlung verläuft die Krankheit in der Regel tödlich. Der einzellige Parasit Trypanosoma brucei ist die Ursache dieser Krankheit. Während seines Lebenszyklus bewegt sich der Parasit zwischen einem Säugetierwirt und einem Insektenvektor, der Tsetsefliege. Im Säugetierwirt vermehrt sich der Parasit als Blutstromform (BSF) extrazellulär im Blutkreislauf und im Lymphsystem. Das Fortbestehen der BSF-Parasiten im Wirt beruht auf einer Immunausweichstrategie durch antigene Variation der Oberflächenproteine. Diese Abwehrstrategie ist erforderlich, da der Parasit durch seinen extrazellulären Lebensstil direkt der Immunantwort ausgesetzt ist. Zu jedem Zeitpunkt wird nur ein variables Oberflächenprotein (VSG) auf der Zelloberfläche aus einem großen Repertoire exprimiert. Dabei wird das aktive VSG von einer von 15 spezialisierten telomerproximalen Transkriptionseinheiten transkribiert, den sogenannten Blutstromform Expression Sites (BESs). Die restlichen 14 BESs sind inaktiv. Diese monoallelische Expression und das periodische Wechseln des exprimierten VSG ermöglichen dem Parasiten der Immunantwort zu entgehen und eine persistente Infektion im Säugetierwirt zu etablieren. Während der Differenzierung von BSF zur Insektenvektor-residenten prozyklischen Form (PCF) wird die aktive BES transkriptionell herunter reguliert um die VSG-Transkription zu stoppen. Somit sind alle 15 BESs in PCF-Zellen inaktiv, da die Expression von Oberflächenproteinen stadienspezifisch reguliert ist. 
Frühere Veröffentlichungen haben gezeigt, dass die Proteine TbTRF, TbRAP1 und TbTIF2 des Telomerkomplexes an der Transkriptionsregulation von VSG-Genen beteiligt sind. Es ist jedoch unklar, wie genau sie zur Regulation beitragen. Darüber hinaus gibt es keine Informationen über die Rolle von Telomeren bei der Initiation und Regulation der BES-Inaktivierung während der Differenzierung. Um Einblicke in die regulatorischen Mechanismen von Telomeren auf die VSG-Transkription und differenzierungsbedingte Repression der aktiven BES zu gewinnen, ist es daher notwendig, die vollständige Zusammensetzung der Telomerkomplexe in Trypanosomen zu identifizieren.
Zu diesem Zweck wurden zwei komplementäre biochemische Ansätze und quantitative Massenspektrometrie genutzt um die Zusammensetzung von Telomerproteinkomplexen in T. brucei zu bestimmen. Zunächst wurden mittels einer Affinitätschromatographie mit TTAGGG-Oligonukleotiden 17 potentielle telomerbindende Proteine gefunden. Darunter waren auch die bereits bekannten telomerbindenden Proteine TbTRF und TbTIF2. Zweitens wurde mit Hilfe eines Co-Immunpräzipitationsexperiments um die Interaktionen von TbTRF aufzuklären, fünf Proteine aufgereinigt. Alle diese fünf Proteine wurden auch mit telomerischer DNA in der Affinitätschromatographie angereichert.
Um diese Daten zu validieren, wurde eines der in beiden Experimenten gefundenen Proteine (TelBP1) charakterisiert. In BSF-Zellen co-lokalisiert TelBP1 mit TbTRF und interagiert mit bereits beschriebenen telomerbindenden Proteinen wie TbTRF, TbTIF2 und TbRAP1. Dies deutet darauf, dass TelBP1 eine weitere Komponente des Telomerkomplexes in Trypanosomen ist. Interessanterweise deuteten Proteininteraktionsstudien in PCF-Zellen auf eine andere Zusammensetzung des Telomerkomplexes im Vergleich zu BSF-Zellen.
Im Gegensatz zu den bekannten Mitgliedern des Telomerkomplexes ist TelBP1 für das Zellwachstum nicht essentiell. Damit könnte die Funktion von TelBP1 von den bekannten telomerbindenden Proteinen entkoppelt sein. Die Überexpression von TelBP1 zeigte auch keinen Einfluss auf das Zellwachstum, führte aber zur Entdeckung von zwei weiteren kürzeren Isoformen von TelBP1. Ihr Ursprung und Funktion blieben jedoch ungeklärt. 
Obwohl TelBP1 für das Zellwachstum entbehrlich ist, zeigten Westernblot-Analysen eine 4-fache Hochregulierung von TelBP1 in BSF-Zellen im Vergleich zu PCF-Zellen. Die stadienspezifische Regulation von TelBP1 unterstützt damit das Konzept von einer dynamischen Zusammensetzung der Telomerkomplexe. Zudem wurde beobachtet, dass TelBP1 die Kinetik der Inaktivierung der aktiven BES während der Differenzierung von der BSF zur PCF beeinflusst. Die Deletion von TelBP1 führte zu einem schnelleren Abschalten der BES im Vergleich zu Wildtyp-Parasiten.
Zusammengefasst zeigt die Funktion von TelBP1, dass das Abschalten der aktiven BES während der Differenzierung ein fein abgestimmter Prozess ist, der stadienspezifische Veränderungen der Telomerkomplexe beinhaltet.
KW  - Trypanosoma brucei
KW  - Genexpression <Molekulargenetik>
KW  - Telomer
KW  - telomere-binding protein
KW  - chromatin remodeling
KW  - developmental differentiation
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-151323
ER  - 
TY  - JOUR
A1  - Hudson, Lawrence N.
A1  - Newbold, Tim
A1  - Contu, Sara
A1  - Hill, Samantha L. L.
A1  - Lysenko, Igor
A1  - De Palma, Adriana
A1  - Phillips, Helen R. P.
A1  - Senior, Rebecca A.
A1  - Bennett, Dominic J.
A1  - Booth, Hollie
A1  - Choimes, Argyrios
A1  - Correia, David L. P.
A1  - Day, Julie
A1  - Echeverria-Londono, Susy
A1  - Garon, Morgan
A1  - Harrison, Michelle L. K.
A1  - Ingram, Daniel J.
A1  - Jung, Martin
A1  - Kemp, Victoria
A1  - Kirkpatrick, Lucinda
A1  - Martin, Callum D.
A1  - Pan, Yuan
A1  - White, Hannah J.
A1  - Aben, Job
A1  - Abrahamczyk, Stefan
A1  - Adum, Gilbert B.
A1  - Aguilar-Barquero, Virginia
A1  - Aizen, Marcelo
A1  - Ancrenaz, Marc
A1  - Arbelaez-Cortes, Enrique
A1  - Armbrecht, Inge
A1  - Azhar, Badrul
A1  - Azpiroz, Adrian B.
A1  - Baeten, Lander
A1  - Báldi, András
A1  - Banks, John E.
A1  - Barlow, Jos
A1  - Batáry, Péter
A1  - Bates, Adam J.
A1  - Bayne, Erin M.
A1  - Beja, Pedro
A1  - Berg, Ake
A1  - Berry, Nicholas J.
A1  - Bicknell, Jake E.
A1  - Bihn, Jochen H.
A1  - Böhning-Gaese, Katrin
A1  - Boekhout, Teun
A1  - Boutin, Celine
A1  - Bouyer, Jeremy
A1  - Brearley, Francis Q.
A1  - Brito, Isabel
A1  - Brunet, Jörg
A1  - Buczkowski, Grzegorz
A1  - Buscardo, Erika
A1  - Cabra-Garcia, Jimmy
A1  - Calvino-Cancela, Maria
A1  - Cameron, Sydney A.
A1  - Cancello, Eliana M.
A1  - Carrijo, Tiago F.
A1  - Carvalho, Anelena L.
A1  - Castro, Helena
A1  - Castro-Luna, Alejandro A.
A1  - Cerda, Rolando
A1  - Cerezo, Alexis
A1  - Chauvat, Matthieu
A1  - Clarke, Frank M.
A1  - Cleary, Daniel F. R.
A1  - Connop, Stuart P.
A1  - D'Aniello, Biagio
A1  - da Silva, Pedro Giovani
A1  - Darvill, Ben
A1  - Dauber, Jens
A1  - Dejean, Alain
A1  - Diekötter, Tim
A1  - Dominguez-Haydar, Yamileth
A1  - Dormann, Carsten F.
A1  - Dumont, Bertrand
A1  - Dures, Simon G.
A1  - Dynesius, Mats
A1  - Edenius, Lars
A1  - Elek, Zoltán
A1  - Entling, Martin H.
A1  - Farwig, Nina
A1  - Fayle, Tom M.
A1  - Felicioli, Antonio
A1  - Felton, Annika M.
A1  - Ficetola, Gentile F.
A1  - Filgueiras, Bruno K. C.
A1  - Fonte, Steve J.
A1  - Fraser, Lauchlan H.
A1  - Fukuda, Daisuke
A1  - Furlani, Dario
A1  - Ganzhorn, Jörg U.
A1  - Garden, Jenni G.
A1  - Gheler-Costa, Carla
A1  - Giordani, Paolo
A1  - Giordano, Simonetta
A1  - Gottschalk, Marco S.
A1  - Goulson, Dave
A1  - Gove, Aaron D.
A1  - Grogan, James
A1  - Hanley, Mick E.
A1  - Hanson, Thor
A1  - Hashim, Nor R.
A1  - Hawes, Joseph E.
A1  - Hébert, Christian
A1  - Helden, Alvin J.
A1  - Henden, John-André
A1  - Hernández, Lionel
A1  - Herzog, Felix
A1  - Higuera-Diaz, Diego
A1  - Hilje, Branko
A1  - Horgan, Finbarr G.
A1  - Horváth, Roland
A1  - Hylander, Kristoffer
A1  - Horváth, Roland
A1  - Isaacs-Cubides, Paola
A1  - Ishitani, Mashiro
A1  - Jacobs, Carmen T.
A1  - Jaramillo, Victor J.
A1  - Jauker, Birgit
A1  - Jonsell, Matts
A1  - Jung, Thomas S.
A1  - Kapoor, Vena
A1  - Kati, Vassiliki
A1  - Katovai, Eric
A1  - Kessler, Michael
A1  - Knop, Eva
A1  - Kolb, Annette
A1  - Körösi, Àdám
A1  - Lachat, Thibault
A1  - Lantschner, Victoria
A1  - Le Féon, Violette
A1  - LeBuhn, Gretchen
A1  - Légaré, Jean-Philippe
A1  - Letcher, Susan G.
A1  - Littlewood, Nick A.
A1  - López-Quintero, Carlos A.
A1  - Louhaichi, Mounir
A1  - Lövei, Gabor L.
A1  - Lucas-Borja, Manuel Esteban
A1  - Luja, Victor H.
A1  - Maeto, Kaoru
A1  - Magura, Tibor
A1  - Mallari, Neil Aldrin
A1  - Marin-Spiotta, Erika
A1  - Marhall, E. J. P.
A1  - Martínez, Eliana
A1  - Mayfield, Margaret M.
A1  - Mikusinski, Gregorz
A1  - Milder, Jeffery C.
A1  - Miller, James R.
A1  - Morales, Carolina L.
A1  - Muchane, Mary N.
A1  - Muchane, Muchai
A1  - Naidoo, Robin
A1  - Nakamura, Akihiro
A1  - Naoe, Shoji
A1  - Nates-Parra, Guiomar
A1  - Navarerete Gutierrez, Dario A.
A1  - Neuschulz, Eike L.
A1  - Noreika, Norbertas
A1  - Norfolk, Olivia
A1  - Noriega, Jorge Ari
A1  - Nöske, Nicole M.
A1  - O'Dea, Niall
A1  - Oduro, William
A1  - Ofori-Boateng, Caleb
A1  - Oke, Chris O.
A1  - Osgathorpe, Lynne M.
A1  - Paritsis, Juan
A1  - Parrah, Alejandro
A1  - Pelegrin, Nicolás
A1  - Peres, Carlos A.
A1  - Persson, Anna S.
A1  - Petanidou, Theodora
A1  - Phalan, Ben
A1  - Philips, T. Keith
A1  - Poveda, Katja
A1  - Power, Eileen F.
A1  - Presley, Steven J.
A1  - Proença, Vânia
A1  - Quaranta, Marino
A1  - Quintero, Carolina
A1  - Redpath-Downing, Nicola A.
A1  - Reid, J. Leighton
A1  - Reis, Yana T.
A1  - Ribeiro, Danilo B.
A1  - Richardson, Barbara A.
A1  - Richardson, Michael J.
A1  - Robles, Carolina A.
A1  - Römbke, Jörg
A1  - Romero-Duque, Luz Piedad
A1  - Rosselli, Loreta
A1  - Rossiter, Stephen J.
A1  - Roulston, T'ai H.
A1  - Rousseau, Laurent
A1  - Sadler, Jonathan P.
A1  - Sáfián, Szbolcs
A1  - Saldaña-Vásquez, Romeo A.
A1  - Samnegård, Ulrika
A1  - Schüepp, Christof
A1  - Schweiger, Oliver
A1  - Sedlock, Jodi L.
A1  - Shahabuddin, Ghazala
A1  - Sheil, Douglas
A1  - Silva, Fernando A. B.
A1  - Slade, Eleanor
A1  - Smith-Pardo, Allan H.
A1  - Sodhi, Navjot S.
A1  - Somarriba, Eduardo J.
A1  - Sosa, Ramón A.
A1  - Stout, Jane C.
A1  - Struebig, Matthew J.
A1  - Sung, Yik-Hei
A1  - Threlfall, Caragh G.
A1  - Tonietto, Rebecca
A1  - Tóthmérész, Béla
A1  - Tscharntke, Teja
A1  - Turner, Edgar C.
A1  - Tylianakis, Jason M.
A1  - Vanbergen, Adam J.
A1  - Vassilev, Kiril
A1  - Verboven, Hans A. F.
A1  - Vergara, Carlos H.
A1  - Vergara, Pablo M.
A1  - Verhulst, Jort
A1  - Walker, Tony R.
A1  - Wang, Yanping
A1  - Watling, James I.
A1  - Wells, Konstans
A1  - Williams, Christopher D.
A1  - Willig, Michael R.
A1  - Woinarski, John C. Z.
A1  - Wolf, Jan H. D.
A1  - Woodcock, Ben A.
A1  - Yu, Douglas W.
A1  - Zailsev, Andreys
A1  - Collen, Ben
A1  - Ewers, Rob M.
A1  - Mace, Georgina M.
A1  - Purves, Drew W.
A1  - Scharlemann, Jörn P. W.
A1  - Pervis, Andy
T1  - The PREDICTS database: a global database of how local terrestrial biodiversity responds to human impacts
JF  - Ecology and Evolution
N2  - Biodiversity continues to decline in the face of increasing anthropogenic pressures such as habitat destruction, exploitation, pollution and introduction of alien species. Existing global databases of species' threat status or population time series are dominated by charismatic species. The collation of datasets with broad taxonomic and biogeographic extents, and that support computation of a range of biodiversity indicators, is necessary to enable better understanding of historical declines and to project - and avert - future declines. We describe and assess a new database of more than 1.6 million samples from 78 countries representing over 28,000 species, collated from existing spatial comparisons of local-scale biodiversity exposed to different intensities and types of anthropogenic pressures, from terrestrial sites around the world. The database contains measurements taken in 208 (of 814) ecoregions, 13 (of 14) biomes, 25 (of 35) biodiversity hotspots and 16 (of 17) megadiverse countries. The database contains more than 1% of the total number of all species described, and more than 1% of the described species within many taxonomic groups - including flowering plants, gymnosperms, birds, mammals, reptiles, amphibians, beetles, lepidopterans and hymenopterans. The dataset, which is still being added to, is therefore already considerably larger and more representative than those used by previous quantitative models of biodiversity trends and responses. The database is being assembled as part of the PREDICTS project (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems - ). We make site-level summary data available alongside this article. The full database will be publicly available in 2015.
KW  - urban-rural gradient
KW  - instensively managed farmland
KW  - Mexican coffee plantations
KW  - Bombus Spp. Hymenoptera
KW  - bumblebee nest density
KW  - data sharing
KW  - land use
KW  - habitat destruction
KW  - global change
KW  - land-use change
KW  - plant community composition
KW  - Northeastern Costa Rica
KW  - dung beetle coleoptera
KW  - bird species richness
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-114425
VL  - 4
IS  - 24
ER  - 
TY  - JOUR
A1  - Reis, Helena
A1  - Schwebs, Marie
A1  - Dietz, Sabrina
A1  - Janzen, Christian J.
A1  - Butter, Falk
T1  - TelAP1 links telomere complexes with developmental expression site silencing in African trypanosomes
JF  - Nucleic Acids Research
N2  - During its life cycle, Trypanosoma brucei shuttles between a mammalian host and the tsetse fly vector. In the mammalian host, immune evasion of T. brucei bloodstream form (BSF) cells relies on antigenic variation, which includes monoallelic expression and periodic switching of variant surface glycoprotein (VSG) genes. The active VSG is transcribed from only 1 of the 15 subtelomeric expression sites (ESs). During differentiation from BSF to the insect-resident procyclic form (PCF), the active ES is transcriptionally silenced. We used mass spectrometry-based interactomics to determine the composition of telomere protein complexes in T. brucei BSF and PCF stages to learn more about the structure and functions of telomeres in trypanosomes. Our data suggest a different telomere complex composition in the two forms of the parasite. One of the novel telomere-associated proteins, TelAP1, forms a complex with telomeric proteins TbTRF, TbRAP1 and TbTIF2 and influences ES silencing kinetics during developmental differentiation.
KW  - Gene Regulation
KW  - Chromatin and Epigenetics
Y1  - 2018
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-225180
VL  - 46
IS  - 6
ER  - 
TY  - JOUR
A1  - Leal, Andrea Zurita
A1  - Schwebs, Marie
A1  - Briggs, Emma
A1  - Weisert, Nadine
A1  - Reis, Helena
A1  - Lemgruber, Leondro
A1  - Luko, Katarina
A1  - Wilkes, Jonathan
A1  - Butter, Falk
A1  - McCulloch, Richard
A1  - Janzen, Christian J.
T1  - Genome maintenance functions of a putative Trypanosoma brucei translesion DNA polymerase include telomere association and a role in antigenic variation
JF  - Nucleic Acids Research
N2  - Maintenance of genome integrity is critical to guarantee transfer of an intact genome from parent to off-spring during cell division. DNA polymerases (Pols) provide roles in both replication of the genome and the repair of a wide range of lesions. Amongst replicative DNA Pols, translesion DNA Pols play a particular role: replication to bypass DNA damage. All cells express a range of translesion Pols, but little work has examined their function in parasites, including whether the enzymes might contribute to host-parasite interactions. Here, we describe a dual function of one putative translesion Pol in African trypanosomes, which we now name TbPolIE. Previously, we demonstrated that TbPolIE is associated with telomeric sequences and here we show that RNAi-mediated depletion of TbPolIE transcripts results in slowed growth, altered DNA content, changes in cell morphology, and increased sensitivity to DNA damaging agents. We also show that TbPolIE displays pronounced localization at the nuclear periphery, and that its depletion leads to chromosome segregation defects and increased levels of endogenous DNA damage. Finally, we demonstrate that TbPolIE depletion leads to deregulation of telomeric variant surface glycoprotein genes, linking the function of this putative translesion DNA polymerase to host immune evasion by antigenic variation.
KW  - cross-link repair
KW  - cell cycle
KW  - gene expression
KW  - low fidelity
KW  - replication
KW  - bypass
KW  - theta
KW  - reveals
KW  - binding
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-230579
VL  - 48
IS  - 17
ER  -