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https://www.readbyqxmd.com/read/29216371/fission-yeast-ccq1-is-a-modulator-of-telomerase-activity
#1
Christine A Armstrong, Vera Moiseeva, Laura C Collopy, Siân R Pearson, Tomalika R Ullah, Shidong T Xi, Jennifer Martin, Shaan Subramaniam, Sara Marelli, Hanna Amelina, Kazunori Tomita
Shelterin, the telomeric protein complex, plays a crucial role in telomere homeostasis. In fission yeast, telomerase is recruited to chromosome ends by the shelterin component Tpz1 and its binding partner Ccq1, where telomerase binds to the 3' overhang to add telomeric repeats. Recruitment is initiated by the interaction of Ccq1 with the telomerase subunit Est1. However, how telomerase is released following elongation remains to be established. Here, we show that Ccq1 also has a role in the suppression of telomere elongation, when coupled with the Clr4 histone H3 methyl-transferase complex and the Clr3 histone deacetylase and nucleosome remodelling complex, SHREC...
December 4, 2017: Nucleic Acids Research
https://www.readbyqxmd.com/read/29203363/mechanism-of-action-of-g-quadruplex-forming-oligonucleotide-homologous-to-the-telomere-overhang-in-melanoma
#2
Gagan Chhabra, Luke Wojdyla, Mark Frakes, Zachary Schrank, Brandon Leviskas, Marko Ivancich, Pooja Vinay, Ramesh Ganapathy, Benjamin E Ramirez, Neelu Puri
T-oligo, a guanine-rich oligonucleotide (GRO) homologous to the 3'-telomeric overhang of telomeres, elicits potent DNA-damage responses in melanoma cells; however, its mechanism of action is largely unknown. GROs can form G-quadruplexes (G4) which are stabilized by the hydrogen-bonding of guanine residues. In this study, we confirmed the G4-forming capabilities of T-oligo using non-denaturing PAGE, NMR and immunofluorescence. Using an anti-G-quadruplex antibody (BG4) we showed that T-oligo can form G4 in the nuclei of melanoma cells...
December 1, 2017: Journal of Investigative Dermatology
https://www.readbyqxmd.com/read/29192673/trfh-domain-at-the-root-of-telomere-protein-evolution
#3
Marie-Joseph Giraud-Panis, Jing Ye, Eric Gilson
Two articles in Cell Research focus on the structure-function relationships in the shelterin complex that binds to telomeres and is essential for their stability and functions. These studies concerning both mammalian and Schizosaccharomyces pombe proteins reveal unexpected structural conservation of a motif called TRFH (Telomeric Repeat Factors Homology) domain between several subunits in these complexes, providing a rationale for further dissection of the role of telomeres in chromosome stability, aging and cancer, and encouraging us to revisit the evolution of telomere proteins...
December 1, 2017: Cell Research
https://www.readbyqxmd.com/read/29160297/structural-and-functional-analyses-of-the-mammalian-tin2-tpp1-trf2-telomeric-complex
#4
Chunyi Hu, Rekha Rai, Chenhui Huang, Cayla Broton, Juanjuan Long, Ying Xu, Jing Xue, Ming Lei, Sandy Chang, Yong Chen
Telomeres are nucleoprotein complexes that play essential roles in protecting chromosome ends. Mammalian telomeres consist of repetitive DNA sequences bound by the shelterin complex. In this complex, the POT1-TPP1 heterodimer binds to single-stranded telomeric DNAs, while TRF1 and TRF2-RAP1 interact with double-stranded telomeric DNAs. TIN2, the linchpin of this complex, simultaneously interacts with TRF1, TRF2, and TPP1 to mediate the stable assembly of the shelterin complex. However, the molecular mechanism by which TIN2 interacts with these proteins to orchestrate telomere protection remains poorly understood...
November 21, 2017: Cell Research
https://www.readbyqxmd.com/read/29160296/structure-of-the-fission-yeast-s-pombe-telomeric-tpz1-poz1-rap1-complex
#5
Jing Xue, Hongwen Chen, Jian Wu, Miho Takeuchi, Haruna Inoue, Yanmei Liu, Hong Sun, Yong Chen, Junko Kanoh, Ming Lei
Telomeric shelterin complex caps chromosome ends and plays a crucial role in telomere maintenance and protection. In the fission yeast Schizosaccharomyces pombe, shelterin is composed of telomeric single- and double-stranded DNA-binding protein subcomplexes Pot1-Tpz1 and Taz1-Rap1, which are bridged by their interacting protein Poz1. However, the structure of Poz1 and how Poz1 functions as an interaction hub in the shelterin complex remain unclear. Here we report the crystal structure of Poz1 in complex with Poz1-binding motifs of Tpz1 and Rap1...
November 21, 2017: Cell Research
https://www.readbyqxmd.com/read/29150048/dna-dependent-protein-kinase-modulates-the-anti-cancer-properties-of-silver-nanoparticles-in-human-cancer-cells
#6
Hui Kheng Lim, Resham Lal Gurung, M Prakash Hande
Silver nanoparticles (Ag-np) were reported to be toxic to eukaryotic cells. These potentially detrimental effects of Ag-np can be advantageous in experimental therapeutics. They are currently being employed to enhance the therapeutic efficacy of cancer drugs. In this study, we demonstrate that Ag-np treatment trigger the activation of DNA-PKcs and JNK pathway at selected doses, presumably as a physiologic response to DNA damage and repair in normal and malignant cells. Ag-np altered the telomere dynamics by disrupting the shelterin complex located at the telomeres and telomere lengths...
December 2017: Mutation Research
https://www.readbyqxmd.com/read/29149597/structural-basis-for-shelterin-bridge-assembly
#7
Jin-Kwang Kim, Jinqiang Liu, Xichan Hu, Clinton Yu, Kyle Roskamp, Banumathi Sankaran, Lan Huang, Elizabeth A Komives, Feng Qiao
Telomere elongation through telomerase enables chromosome survival during cellular proliferation. The conserved multifunctional shelterin complex associates with telomeres to coordinate multiple telomere activities, including telomere elongation by telomerase. Similar to the human shelterin, fission yeast shelterin is composed of telomeric sequence-specific double- and single-stranded DNA-binding proteins, Taz1 and Pot1, respectively, bridged by Rap1, Poz1, and Tpz1. Here, we report the crystal structure of the fission yeast Tpz1(475-508)-Poz1-Rap1(467-496) complex that provides the structural basis for shelterin bridge assembly...
November 16, 2017: Molecular Cell
https://www.readbyqxmd.com/read/29149592/dynamics-under-the-telomeric-bridge
#8
Sabrina Pisano, Eric Gilson, Marie-Josèphe Giraud-Panis
In this issue of Molecular Cell, Kim et al. (2017) have studied the structure and organization of the shelterin protein complex protecting telomeres in Schizosaccharomyces pombe and humans and discovered an allosteric structural transition that drives the formation of the shelterin complex and participates in telomere length regulation.
November 16, 2017: Molecular Cell
https://www.readbyqxmd.com/read/29137380/inhibitors-of-telomerase-and-poly-adp-ribose-polymerases-synergize-to-limit-the-lifespan-of-pancreatic-cancer-cells
#9
Katrina M Burchett, Asserewou Etekpo, Surinder K Batra, Ying Yan, Michel M Ouellette
Imetelstat (GRN163L) is a potent and selective inhibitor of telomerase. We have previously reported that GRN163L could shorten telomeres and limit the lifespan of CD18/HPAF and CAPAN1 pancreatic cancer cells. Here, we examined the effects of GRN163L on two other pancreatic cancer cell lines: AsPC1 and L3.6pl. In both lines, chronic exposure to GRN163L led to an initial shortening of telomeres followed by a stabilization of extremely short telomeres. In AsPC1 cells, telomere attrition eventually led to the induction of crisis and the loss of the treated population...
October 13, 2017: Oncotarget
https://www.readbyqxmd.com/read/29134494/expression-of-telomere-associated-proteins-is-interdependent-to-stabilize-native-telomere-structure-and-telomere-dysfunction-by-g-quadruplex-ligand-causes-terra-upregulation
#10
Ratan Sadhukhan, Priyanka Chowdhury, Sourav Ghosh, Utpal Ghosh
Telomere DNA can form specialized nucleoprotein structure with telomere-associated proteins to hide free DNA ends or G-quadruplex structures under certain conditions especially in presence of G-quadruplex ligand. Telomere DNA is transcribed to form non-coding telomere repeat-containing RNA (TERRA) whose biogenesis and function is poorly understood. Our aim was to find the role of telomere-associated proteins and telomere structures in TERRA transcription. We silenced four [two shelterin (TRF1, TRF2) and two non-shelterin (PARP-1, SLX4)] telomere-associated genes using siRNA and verified depletion in protein level...
November 13, 2017: Cell Biochemistry and Biophysics
https://www.readbyqxmd.com/read/29126443/ubiquitin-c-terminal-hydrolase-isozyme-l1-is-associated-with-shelterin-complex-at-interstitial-telomeric-sites
#11
Aleksandar Ilic, Sumin Lu, Vikram Bhatia, Farhana Begum, Thomas Klonisch, Prasoon Agarwal, Wayne Xu, James R Davie
BACKGROUND: Ubiquitin C-terminal hydrolase isozyme L1 (UCHL1) is primarily expressed in neuronal cells and neuroendocrine cells and has been associated with various diseases, including many cancers. It is a multifunctional protein involved in deubiquitination, ubiquitination and ubiquitin homeostasis, but its specific roles are disputed and still generally undetermined. RESULTS: Herein, we demonstrate that UCHL1 is associated with genomic DNA in certain prostate cancer cell lines, including DU 145 cells derived from a brain metastatic site, and in HEK293T embryonic kidney cells with a neuronal lineage...
November 10, 2017: Epigenetics & Chromatin
https://www.readbyqxmd.com/read/29097657/modulation-of-telomere-protection-by-the-pi3k-akt-pathway
#12
Marinela Méndez-Pertuz, Paula Martínez, Carmen Blanco-Aparicio, Elena Gómez-Casero, Ana Belen García, Jorge Martínez-Torrecuadrada, Marta Palafox, Javier Cortés, Violeta Serra, Joaquin Pastor, Maria A Blasco
Telomeres and the insulin/PI3K pathway are considered hallmarks of aging and cancer. Here, we describe a role for PI3K/AKT in the regulation of TRF1, an essential component of the shelterin complex. PI3K and AKT chemical inhibitors reduce TRF1 telomeric foci and lead to increased telomeric DNA damage and fragility. We identify the PI3Kα isoform as responsible for this TRF1 inhibition. TRF1 is phosphorylated at different residues by AKT and these modifications regulate TRF1 protein stability and TRF1 binding to telomeric DNA in vitro and are important for in vivo TRF1 telomere location and cell viability...
November 2, 2017: Nature Communications
https://www.readbyqxmd.com/read/29083416/telomeric-terb1-trf1-interaction-is-crucial-for-male-meiosis
#13
Juanjuan Long, Chenhui Huang, Yanyan Chen, Ying Zhang, Shaohua Shi, Ligang Wu, Yie Liu, Chengyu Liu, Jian Wu, Ming Lei
During meiotic prophase, the meiosis-specific telomere-binding protein TERB1 regulates chromosome movement required for homologous pairing and recombination by interacting with the telomeric shelterin subunit TRF1. Here, we report the crystal structure of the TRF1-binding motif of human TERB1 in complex with the TRFH domain of TRF1. Notably, specific disruption of the TERB1-TRF1 interaction by a point mutation in the mouse Terb1 gene results in infertility only in males. We find that this mutation causes an arrest in the zygotene-early pachytene stage and mild telomere abnormalities of autosomes but unpaired X and Y chromosomes in pachytene, leading to massive spermatocyte apoptosis...
October 30, 2017: Nature Structural & Molecular Biology
https://www.readbyqxmd.com/read/29057866/reconstitution-of-human-shelterin-complexes-reveals-unexpected-stoichiometry-and-dual-pathways-to-enhance-telomerase-processivity
#14
Ci Ji Lim, Arthur J Zaug, Hee Jin Kim, Thomas R Cech
The human shelterin proteins associate with telomeric DNA to confer telomere protection and length regulation. They are thought to form higher-order protein complexes for their functions, but studies of shelterin proteins have been mostly limited to pairs of proteins. Here we co-express various human shelterin proteins and find that they form defined multi-subunit complexes. A complex harboring both TRF2 and POT1 has the strongest binding affinity to telomeric DNA substrates comprised of double-stranded DNA with a 3' single-stranded extension...
October 20, 2017: Nature Communications
https://www.readbyqxmd.com/read/29055871/acute-telomerase-components-depletion-triggers-oxidative-stress-as-an-early-event-previous-to-telomeric-shortening
#15
José Santiago Ibáñez-Cabellos, Giselle Pérez-Machado, Marta Seco-Cervera, Ester Berenguer-Pascual, José Luis García-Giménez, Federico V Pallardó
Loss of function of dyskerin (DKC1), NOP10 and TIN2 are responsible for different inheritance patterns of Dyskeratosis congenita (DC; ORPHA1775). They are key components of telomerase (DKC1 and NOP10) and shelterin (TIN2), and play an important role in telomere homeostasis. They participate in several fundamental cellular processes by contributing to Dyskeratosis congenita through mechanisms that are not fully understood. Presence of oxidative stress was postulated to result from telomerase ablation. However, the resulting disturbed redox status can promote telomere attrition by generating a vicious circle, which promotes cellular senescence...
October 7, 2017: Redox Biology
https://www.readbyqxmd.com/read/29043869/identifying-the-biomarker-potential-of-telomerase-activity-and-shelterin-complex-molecule-telomeric-repeat-binding-factor-2-terf2-in-multiple-myeloma
#16
Raman Kumar, Rehan Khan, Nidhi Gupta, Tulika Seth, Atul Sharma, Mani Kalaivani, Alpana Sharma
Telomere length (TL) is maintained by telomere capping protein complex called shelterin complex. We studied the possible involvement and biomarker potential of shelterin complex molecules in naive multiple myeloma (MM) patients and controls. TL, relative telomerase activity (RTA), real-time PCR and Western blotting were performed in bonemarrow sample of 70 study subjects (patients = 50; controls = 20). Significantly lowered mean TL, increased RTA and higher mRNA expression of shelterin molecules were observed in patients, while PIN2/TERF1 interacting telomerase inhibitor 1 (PINX1) showed lower mRNA expression...
October 18, 2017: Leukemia & Lymphoma
https://www.readbyqxmd.com/read/28986560/the-telomere-binding-protein-pot1-maintains-haematopoietic-stem-cell-activity-with-age
#17
Kentaro Hosokawa, Ben D MacArthur, Yoshiko Matsumoto Ikushima, Hirofumi Toyama, Yoshikazu Masuhiro, Shigemasa Hanazawa, Toshio Suda, Fumio Arai
Repeated cell divisions and aging impair stem cell function. However, the mechanisms by which this occurs are not fully understood. Here we show that protection of telomeres 1A (Pot1a), a component of the Shelterin complex that protects telomeres, improves haematopoietic stem cell (HSC) activity during aging. Pot1a is highly expressed in young HSCs, but declines with age. In mouse HSCs, Pot1a knockdown increases DNA damage response (DDR) and inhibits self-renewal. Conversely, Pot1a overexpression or treatment with POT1a protein prevents DDR, maintained self-renewal activity and rejuvenated aged HSCs upon ex vivo culture...
October 6, 2017: Nature Communications
https://www.readbyqxmd.com/read/28955502/systematic-analysis-of-human-telomeric-dysfunction-using-inducible-telosome-shelterin-crispr-cas9-knockout-cells
#18
Hyeung Kim, Feng Li, Quanyuan He, Tingting Deng, Jun Xu, Feng Jin, Cristian Coarfa, Nagireddy Putluri, Dan Liu, Zhou Songyang
CRISPR/Cas9 technology enables efficient loss-of-function analysis of human genes using somatic cells. Studies of essential genes, however, require conditional knockout (KO) cells. Here, we describe the generation of inducible CRISPR KO human cell lines for the subunits of the telosome/shelterin complex, TRF1, TRF2, RAP1, TIN2, TPP1 and POT1, which directly interact with telomeres or can bind to telomeres through association with other subunits. Homozygous inactivation of several subunits is lethal in mice, and most loss-of-function studies of human telomere regulators have relied on RNA interference-mediated gene knockdown, which suffers its own limitations...
2017: Cell Discovery
https://www.readbyqxmd.com/read/28944611/gene-therapy-with-the-trf1-telomere-gene-rescues-decreased-trf1-levels-with-aging-and-prolongs-mouse-health-span
#19
Aksinya Derevyanko, Kurt Whittemore, Ralph P Schneider, Verónica Jiménez, Fàtima Bosch, Maria A Blasco
The shelterin complex protects telomeres by preventing them from being degraded and recognized as double-strand DNA breaks. TRF1 is an essential component of shelterin, with important roles in telomere protection and telomere replication. We previously showed that TRF1 deficiency in the context of different mouse tissues leads to loss of tissue homeostasis owing to impaired stem cell function. Here, we show that TRF1 levels decrease during organismal aging both in mice and in humans. We further show that increasing TRF1 expression in both adult (1-year-old) and old (2-year-old) mice using gene therapy can delay age-associated pathologies...
December 2017: Aging Cell
https://www.readbyqxmd.com/read/28943299/interaction-of-quindoline-derivative-with-telomeric-repeat-containing-rna-induces-telomeric-dna-damage-response-in-cancer-cells-through-inhibition-of-telomeric-repeat-factor-2
#20
Yan Zhang, Deying Zeng, Jiaojiao Cao, Mingxue Wang, Bing Shu, Guotao Kuang, Tian-Miao Ou, Jia-Heng Tan, Lian-Quan Gu, Zhi-Shu Huang, Ding Li
BACKGROUND: Telomeric repeat-containing RNA (TERRA) is a large non-coding RNA in mammalian cells, which forms an integral component of telomeric heterochromatin. TERRA can bind to an allosteric site of telomeric repeat factor 2 (TRF2), a key component of Shelterin that protect chromosome termini. Both TERRA and TRF2 have been recognized as promising new therapeutic targets for cancer treatment. METHODS: Our methods include FRET assay, SPR, CD, microscale thermophoresis (MST), enzyme-linked immunosorbent assay (ELISA), chromatin immunoprecipitation (ChIP), colony formation assays, Western blot, immunofluorescence, cell cycle arrest and apoptosis detection, and xCELLigence real-time cell analysis (RTCA)...
December 2017: Biochimica et Biophysica Acta
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