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https://www.readbyqxmd.com/read/29428209/the-structurally-similar-trfh-domain-of-trf1-and-trf2-dimers-shows-distinct-behaviour-towards-tin2
#1
Umesh Kalathiya, Monikaben Padariya, Maciej Baginski
The telomere repeat binding-factor 1 and 2 (TRF1 and TRF2) proteins of the shelterin complex bind to duplex telomeric DNA as homodimers, and the homodimerization is mediated by their TRFH (TRF-homology) domains. We performed molecular dynamic (MD) simulations of the dimer forms of TRF1TRFH and TRF2TRFH in the presence/absence of the TIN2TBM (TIN2, TRF-interacting nuclear protein 2, TBM, TRF-binding motif) peptide. The MD results suggest that TIN2TBM is necessary to ensure the stability of TRF1TRFH homodimer but not the TRF2TRFH homodimer...
February 8, 2018: Archives of Biochemistry and Biophysics
https://www.readbyqxmd.com/read/29358759/trf1-participates-in-chromosome-end-protection-by-averting-trf2-dependent-telomeric-r-loops
#2
Yong Woo Lee, Rajika Arora, Harry Wischnewski, Claus M Azzalin
The shelterin protein TRF2 assembles protective T loops at chromosome ends by stimulating intramolecular invasion of the telomeric G-rich single-stranded DNA (ssDNA) overhang into the duplex telomeric array. The other shelterin factor, TRF1, is thought to mainly facilitate telomeric dsDNA replication without directly participating in end protection. Here we show that in vitro human TRF2 stimulates invasion of G-rich TERRA-like RNA into telomeric dsDNA, leading to formation of telomeric RNA-DNA hybrids (telR loops)...
January 22, 2018: Nature Structural & Molecular Biology
https://www.readbyqxmd.com/read/29335368/in-medio-stat-virtus-unanticipated-consequences-of-telomere-dysequilibrium
#3
REVIEW
Lea Harrington, Fabio Pucci
The integrity of chromosome ends, or telomeres, depends on myriad processes that must balance the need to compact and protect the telomeric, G-rich DNA from detection as a double-stranded DNA break, and yet still permit access to enzymes that process, replicate and maintain a sufficient reserve of telomeric DNA. When unable to maintain this equilibrium, erosion of telomeres leads to perturbations at or near the telomeres themselves, including loss of binding by the telomere protective complex, shelterin, and alterations in transcription and post-translational modifications of histones...
March 5, 2018: Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences
https://www.readbyqxmd.com/read/29331736/dysfunctional-telomeres-and-hematological-disorders
#4
REVIEW
Elena Fiorini, Andrea Santoni, Simona Colla
Telomere biology disorders, which are characterized by telomerase activity haploinsufficiency and accelerated telomere shortening, most commonly manifest as degenerative diseases. Tissues with high rates of cell turnover, such as those in the hematopoietic system, are particularly vulnerable to defects in telomere maintenance genes that eventually culminate in bone marrow (BM) failure syndromes, in which the BM cannot produce sufficient new blood cells. Here, we review how telomere defects induce degenerative phenotypes across multiple organs, with particular focus on how they impact the hematopoietic stem and progenitor compartment and affect hematopoietic stem cell (HSC) self-renewal and differentiation...
January 4, 2018: Differentiation; Research in Biological Diversity
https://www.readbyqxmd.com/read/29311622/dual-roles-of-trf1-in-tethering-telomeres-to-the-nuclear-envelope-and-protecting-them-from-fusion-during-meiosis
#5
Lina Wang, Zhaowei Tu, Chao Liu, Hongbin Liu, Philipp Kaldis, Zijiang Chen, Wei Li
Telomeres integrity is indispensable for chromosomal stability by preventing chromosome erosion and end-to-end fusions. During meiosis, telomeres attach to the inner nuclear envelope and cluster into a highly crowded microenvironment at the bouquet stage, which requires specific mechanisms to protect the telomeres from fusion. Here, we demonstrate that germ cell-specific knockout of a shelterin complex subunit, Trf1, results in arrest of spermatocytes at two different stages. The obliterated telomere-nuclear envelope attachment in Trf1-deficient spermatocytes impairs homologue synapsis and recombination, resulting in a pachytene-like arrest, while the meiotic division arrest might stem from chromosome end-to-end fusion due to the failure of recruiting meiosis specific telomere associated proteins...
January 8, 2018: Cell Death and Differentiation
https://www.readbyqxmd.com/read/29305433/pinx1-and-tert-are-required-for-tnf-%C3%AE-induced-airway-smooth-muscle-chemokine-gene-expression
#6
Karl Deacon, Alan J Knox
Airway smooth muscle (ASM) cells contribute to asthmatic lung pathology with chemokine hypersecretion and increased ASM cell mass. With little recent progress in the development of asthma therapies, a greater understanding of lung inflammation mechanisms has become a priority. Chemokine gene expression in ASM cells is dependent upon NF-κB transcription factor activity. The telomerase/shelterin complex maintains chromosomal telomere ends during cell division. Telomerase is a possible cofactor for NF-κB activity, but its role in NF-κB activity in airway tissue inflammation is not known...
January 5, 2018: Journal of Immunology: Official Journal of the American Association of Immunologists
https://www.readbyqxmd.com/read/29240257/altered-expression-of-telomere-associated-genes-in-leukocytes-among-brca1-and-brca2-carriers
#7
Hiromi Tanaka, Elizabeth A Phipps, Ting Wei, Xi Wu, Chirayu Goswami, Yunlong Liu, George W Sledge, Lida Mina, Brittney-Shea Herbert
Telomere dysfunction resulting from telomere shortening and deregulation of shelterin components has been linked to the pathogenesis of age-related disorders, including cancer. Recent evidence suggests that BRCA1/2 (BRCA1 and BRCA2) tumor suppressor gene products play an important role in telomere maintenance. Although telomere shortening has been reported in BRCA1/2 carriers, the direct effects of BRCA1/2 haploinsufficiency on telomere maintenance and predisposition to cancer development are not completely understood...
December 14, 2017: Molecular Carcinogenesis
https://www.readbyqxmd.com/read/29227966/pot1-inhibits-the-efficiency-but-promotes-the-fidelity-of-nonhomologous-end-joining-at-non-telomeric-dna-regions
#8
Yang Yu, Rong Tan, Qian Ren, Boya Gao, Zhejin Sheng, Juanlian Zhang, Xiaoqing Zheng, Ying Jiang, Li Lan, Zhiyong Mao
Robust DNA double strand break (DSB) repair and stabilized telomeres help maintain genome integrity, preventing the onset of aging or tumorigenesis. POT1 is one of the six factors in the shelterin complex, which protects telomeres from being recognized as DNA damages. TRF1 and TRF2, two other shelterin proteins, have been shown to participate in DNA DSB repair at non-telomeric regions, but whether POT1, which binds to single strand telomeric DNA at chromosomal ends, is involved in DNA DSB repair has not been assessed...
December 8, 2017: Aging
https://www.readbyqxmd.com/read/29216371/fission-yeast-ccq1-is-a-modulator-of-telomerase-activity
#9
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
#10
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
#11
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
#12
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
#13
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...
December 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
#14
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
#15
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
#16
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
#17
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
#18
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
#19
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
#20
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
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