scholarly journals The Telomerase/Vault-Associated Protein Tep1 Is Required for Vault RNA Stability and Its Association with the Vault Particle

2001 ◽  
Vol 152 (1) ◽  
pp. 157-164 ◽  
Author(s):  
Valerie A. Kickhoefer ◽  
Yie Liu ◽  
Lawrence B. Kong ◽  
Bryan E. Snow ◽  
Phoebe L. Stewart ◽  
...  
Keyword(s):  
Rna Stability ◽  
Three Dimensional ◽  
Telomerase Activity ◽  
Telomerase Rna ◽  
Protein Subunit ◽  
Negative Stain ◽  
Dimensional Reconstruction ◽  
Stable Association ◽  
Vault Rna

Vaults and telomerase are ribonucleoprotein (RNP) particles that share a common protein subunit, TEP1. Although its role in either complex has not yet been defined, TEP1 has been shown to interact with the mouse telomerase RNA and with several of the human vault RNAs in a yeast three-hybrid assay. An mTep1−/− mouse was previously generated which resulted in no apparent change in telomere length or telomerase activity in six generations of mTep1-deficient mice. Here we show that the levels of the telomerase RNA and its association with the telomerase RNP are also unaffected in mTep1−/− mice. Although vaults purified from the livers of mTep1−/− mice appear structurally intact by both negative stain and cryoelectron microscopy, three-dimensional reconstruction of the mTep1−/− vault revealed less density in the cap than previously observed for the intact rat vault. Furthermore, the absence of TEP1 completely disrupted the stable association of the vault RNA with the purified vault particle and also resulted in a decrease in the levels and stability of the vault RNA. Therefore, we have uncovered a novel role for TEP1 in vivo as an integral vault protein important for the stabilization and recruitment of the vault RNA to the vault particle.

scholarly journals A 4-base pair core-enclosing helix in telomerase RNA is essential and binds to the TERT catalytic protein subunit

2020 ◽  
Author(s):  
Melissa A. Mefford ◽  
Evan P. Hass ◽  
David C. Zappulla
Keyword(s):  
Telomerase Activity ◽  
Genome Replication ◽  
Telomerase Rna ◽  
Protein Subunit ◽  
Base Pairs ◽  
Binding Interaction ◽  
Catalytic Core ◽  
Yeast Telomerase

ABSTRACTThe telomerase RNP counters the chromosome end-replication problem, completing genome replication to prevent cellular senescence in yeast, humans, and most other eukaryotes. The telomerase RNP core enzyme is composed of a dedicated RNA subunit and a reverse transcriptase (TERT). Although the majority of the 1157-nt Saccharomyces cerevisiae telomerase RNA, TLC1, is rapidly evolving, the central catalytic core is largely conserved, containing the template, template-boundary helix, pseudoknot, and core-enclosing helix (CEH). Here, we show that 4-base pairs of core-enclosing helix is required for telomerase to be active in vitro and to maintain yeast telomeres in vivo, whereas ΔCEH, 1-bp, and 2-bp alleles do not support telomerase function. Using the CRISPR/dCas9-based “CARRY two-hybrid” assay to assess binding of our CEH mutant RNAs to TERT, we find that the 4-bp CEH RNA binds to TERT, but the shorter-CEH constructs do not, consistent with the telomerase activity and in vivo complementation results. Thus, the CEH is essential in yeast telomerase RNA because it is needed to bind TERT to form the core RNP enzyme. Although the 8 nucleotides that form this 4-bp stem at the base of the CEH are nearly invariant among Saccharomyces species, our results with sequence-randomized and truncated-CEH helices strongly suggest that this binding interaction with TERT is dictated more by secondary than primary structure. In summary, we have mapped an essential binding site in telomerase RNA for TERT that is crucial to form the catalytic core of this biomedically important RNP enzyme.

The Three-dimensional structure of frozen-hydrated nudaurelia capensis β virus

1987 ◽  
Vol 45 ◽  
pp. 650-651
Author(s):  
N. H. Olson ◽  
T. S. Baker ◽  
Wu Bo Mu ◽  
J. E. Johnson ◽  
D. A. Hendry
Keyword(s):  
South African ◽  
Rna Virus ◽  
Carbon Film ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Electron Dose ◽  
Total Electron ◽  
Three Dimensional Structure ◽  
Negative Stain ◽  
Dimensional Reconstruction

Nudaurelia capensis β virus (NβV) is an RNA virus of the South African Pine Emperor moth, Nudaurelia cytherea capensis (Lepidoptera: Saturniidae). The NβV capsid is a T = 4 icosahedron that contains 60T = 240 subunits of the coat protein (Mr = 61,000). A three-dimensional reconstruction of the NβV capsid was previously computed from visions embedded in negative stain suspended over holes in a carbon film. We have re-examined the three-dimensional structure of NβV, using cryo-microscopy to examine the native, unstained structure of the virion and to provide a initial phasing model for high-resolution x-ray crystallographic studiesNβV was purified and prepared for cryo-microscopy as described. Micrographs were recorded ∼1 - 2 μm underfocus at a magnification of 49,000X with a total electron dose of about 1800 e-/nm2.

scholarly journals The conserved structure of plant telomerase RNA provides the missing link for an evolutionary pathway from ciliates to humans

2019 ◽  
Vol 116 (49) ◽  
pp. 24542-24550 ◽  
Author(s):  
Jiarui Song ◽  
Dhenugen Logeswaran ◽  
Claudia Castillo-González ◽  
Yang Li ◽  
Sreyashree Bose ◽  
...  
Keyword(s):  
Telomerase Activity ◽  
Telomere Maintenance ◽  
Telomerase Rna ◽  
Telomeric Dna ◽  
Structural Element ◽  
Stem Loop ◽  
Evolutionary Pathway ◽  
Pol Iii

Telomerase is essential for maintaining telomere integrity. Although telomerase function is widely conserved, the integral telomerase RNA (TR) that provides a template for telomeric DNA synthesis has diverged dramatically. Nevertheless, TR molecules retain 2 highly conserved structural domains critical for catalysis: a template-proximal pseudoknot (PK) structure and a downstream stem-loop structure. Here we introduce the authentic TR from the plant Arabidopsis thaliana, called AtTR, identified through next-generation sequencing of RNAs copurifying with Arabidopsis TERT. This RNA is distinct from the RNA previously described as the templating telomerase RNA, AtTER1. AtTR is a 268-nt Pol III transcript necessary for telomere maintenance in vivo and sufficient with TERT to reconstitute telomerase activity in vitro. Bioinformatics analysis identified 85 AtTR orthologs from 3 major clades of plants: angiosperms, gymnosperms, and lycophytes. Through phylogenetic comparisons, a secondary structure model conserved among plant TRs was inferred and verified using in vitro and in vivo chemical probing. The conserved plant TR structure contains a template-PK core domain enclosed by a P1 stem and a 3′ long-stem P4/5/6, both of which resemble a corresponding structural element in ciliate and vertebrate TRs. However, the plant TR contains additional stems and linkers within the template-PK core, allowing for expansion of PK structure from the simple PK in the smaller ciliate TR during evolution. Thus, the plant TR provides an evolutionary bridge that unites the disparate structures of previously characterized TRs from ciliates and vertebrates.

scholarly journals Measurements of the wall shear stress distribution in the outflow tract of an embryonic chicken heart

2009 ◽  
Vol 7 (42) ◽  
pp. 91-103 ◽  
Author(s):  
C. Poelma ◽  
K. Van der Heiden ◽  
B. P. Hierck ◽  
R. E. Poelmann ◽  
J. Westerweel
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Three Dimensional ◽  
Outflow Tract ◽  
Chicken Heart ◽  
Embryonic Chicken ◽  
Dimensional Reconstruction ◽  
Wall Shear ◽  
Embryo Heart

In order to study the role of blood–tissue interaction in the developing chicken embryo heart, detailed information about the haemodynamic forces is needed. In this study, we present the first in vivo measurements of the three-dimensional distribution of wall shear stress (WSS) in the outflow tract (OFT) of an embryonic chicken heart. The data are obtained in a two-step process: first, the three-dimensional flow fields are measured during the cardiac cycle using scanning microscopic particle image velocimetry; second, the location of the wall and the WSS are determined by post-processing flow velocity data (finding velocity gradients at locations where the flow approaches zero). The results are a three-dimensional reconstruction of the geometry, with a spatial resolution of 15–20 µm, and provides detailed information about the WSS in the OFT. The most significant error is the location of the wall, which results in an estimate of the uncertainty in the WSS values of 20 per cent.

Ultrasonic three-dimensional reconstruction: In vitro and In vivo volume and area measurement

1994 ◽  
Vol 20 (8) ◽  
pp. 719-729 ◽  
Author(s):  
Timothy C. Hodges ◽  
Paul R. Detmer ◽  
David H. Burns ◽  
Kirk W. Beach ◽  
D.Eugene Strandness
Keyword(s):  
Three Dimensional ◽  
Area Measurement ◽  
Three Dimensional Reconstruction ◽  
Dimensional Reconstruction

Targeting prostate cancer progenitor cells with telomerase interference: A novel therapeutic strategy

2009 ◽  
Vol 27 (15_suppl) ◽  
pp. e22029-e22029
Author(s):  
A. Goldkorn ◽  
T. Xu
Keyword(s):  
Gene Expression ◽  
Prostate Cancer ◽  
Progenitor Cells ◽  
Cancer Progression ◽  
Cell Activation ◽  
Telomerase Activity ◽  
Human Prostate ◽  
Telomerase Rna ◽  
Prostate Tumors

e22029 Background: We investigated whether telomerase, which is critical for benign stem cell activation, also plays a role in prostate cancer progenitor cells (PCPCs), which are thought to mediate therapy resistance and cancer progression, and we tested whether telomerase interference can effectively inhibit PCPC proliferation. Methods: A putative PCPC population was isolated from human prostatectomy specimens via collagen attachment and FACS selection for integrin α2β1 and CD44. PCPCs were characterized for gene expression (RT-PCR), clonogenicity (colony formation), invasiveness (matrigel chamber), and telomerase activity (qPCR-TRAP). PCPC telomerase interference was accomplished by lentiviral expression of 2 constructs: telomerase RNA with an altered template region (MT-Ter) and siRNA targeting wild-type telomerase RNA (anti-Ter siRNA). The effects of these constructs were assessed by measuring PCPC viability (MTS) and apoptosis (TUNEL assay). Results: An integrin α2β1+CD44+ putative PCPC population was isolated from 6 human prostate tumors. This population expressed high levels of “progenitor phenotype” genes (ABCG2, β-catenin, NANOG, Oct3/4) and low levels of “differentiated phenotype” genes (AR and PSA). PCPCs yielded >50 colonies per 1000 cells seeded on collagen after 3 weeks vs. none from FACS- cells, and matrigel chamber assay showed 10% of the PCPC population invading over 24 hours vs. none of the FACS- population. Most importantly, PCPCs possessed at least 20- fold greater telomerase activity than FACS- cells, and induction of telomerase interference in PCPCs via MT-hTer and anti- hTer siRNA expression elicited a brisk apoptotic response (TUNEL) by day 3 in >90% of cells, with concomitant near-complete growth inhibition (MTS). Conclusions: We have shown that human prostate tumors contain a subpopulation of prostate cancer progenitor cells (PCPCs) marked by an undifferentiated gene expression profile, vigorous clonogenicity and invasiveness, and high levels of telomerase activity that can be successfully exploited to neutralize these cells. Ongoing studies are investigating the in vivo effects of telomerase interference on PCPC tumorigenicity in mouse models. No significant financial relationships to disclose.

Mouse prostate tumor inhibition via disruption of murine telomerase: In vivo and in vitro data for a new preclinical cancer model

2009 ◽  
Vol 27 (15_suppl) ◽  
pp. e14631-e14631
Author(s):  
T. Xu ◽  
Y. Xu ◽  
R. Lao ◽  
K. He ◽  
L. Xue ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Dna Damage ◽  
Cancer Cells ◽  
Cancer Cell Line ◽  
Telomerase Activity ◽  
Telomerase Rna ◽  
Prostate Cancer Cells ◽  
Mouse Prostate

e14631 Background: Telomerase-interference (TI), a novel therapeutic strategy, exploits the high telomerase activity in prostate cancer by introducing a mutated telomerase RNA (MT-Ter) that encodes toxic telomeres. Until now, TI has been tested by targeting human telomerase in tumor cells xenografted into immuno-deficient mice, an inadequate model for predicting efficacy and toxicity. We designed and validated 2 new TI gene constructs that specifically target murine telomerase RNA (mTER), enabling the study of TI in preclinical mouse models that are immuno-competent and that develop endogenous prostate tumors. Methods: We designed 2 constructs and cloned them into a lentiviral delivery system: MT-mTER and siRNA against wild type mTer (α-mTer-siRNA). Using a mouse prostate cancer cell line, E4, we tested the 2 constructs for expression (RT-PCR), telomerase activity (TRAP), and biologic activity (53bp1 DNA damage staining, MTS growth assay, TUNEL and caspase apoptosis assays), as well as in vivo efficacy (NOD-SCID allografts). Results: We confirmed MT-mTER expression (∼50-fold) and showed that α-mTer-siRNA specifically depleted WT-mTER (80% reduction) but not MT-mTER when the 2 constructs are co-expressed; thus, the 2 constructs in combination effectively substituted MT-mTer for WT-mTer in the mouse prostate cancer cells. MT-mTER caused mutant telomeric repeats (TTTGGG instead of TTAGGG) to be added to the ends of telomeres, resulting in rapid telomeric uncapping marked by 53bp1 DNA damage foci (an average 7.5 foci/cell vs. 1.4 foci/cell in vector control). This, in turn, led to rapid and significant apoptosis (>90% TUNEL and caspase +) and growth inhibition in vitro (90% reduction by MTS) and in vivo (75% reduction in tumor allograft size). Conclusions: We successfully designed and validated MT-mTer and α-mTer-siRNA, 2 novel gene constructs that specifically target and co-opt murine telomerase activity within mouse prostate cancer cells. These constructs offer a significant advantage, as they can be used to investigate TI in immuno-competent mice that develop prostate cancer, thereby modeling actual human disease and testing TI-based therapies in a much more informative and authentic manner. No significant financial relationships to disclose.

SIMULATION OF VESSEL STRESS AND SECONDARY FLOWS FOR BLOOD FLOWS THROUGH A REALISTIC AORTA WITH THREE BRANCHES

2007 ◽  
Vol 19 (04) ◽  
pp. 215-223 ◽  
Author(s):  
Yang-Yao Niu ◽  
Pang-Chung Wu ◽  
Wen-Yih I. Tseng ◽  
Hsi-Yu Yu
Keyword(s):  
Secondary Flow ◽  
Aortic Arch ◽  
Three Dimensional ◽  
Wall Stress ◽  
Outer Wall ◽  
Secondary Flows ◽  
Blood Flows ◽  
Flow Recirculation ◽  
Dimensional Reconstruction

Blood secondary flows and vessel wall shear stress distributions in a human aortic arch have been predicted numerically for a Reynolds number of 4700 at entrance. The simulation geometry was derived from a three-dimensional reconstruction of a series of two-dimensional slices obtained in vivo. Numerical results demonstrate wall stresses were highly dynamic, but were generally high along the outer wall in the vicinity of the branches and low along the inner wall, particularly in the descending thoracic aorta. The maximum wall stress distribution is presented on the aortic arch in the systole. Extensive secondary flow motion was observed in the aorta, and the structure of these secondary flows was influenced considerably by the presence of the branches. Within the aorta, it is observed that clockwise secondary flow recirculation, also seen in the MRA scan data, appears in the downstream of aortic arch in the late systole and turn out to be a pair of counter-clockwise vortex in the downstream of the arch in the early diastole.

scholarly journals Polymerization Defects within Human Telomerase Are Distinct from Telomerase RNA and TEP1 Binding

2000 ◽  
Vol 11 (10) ◽  
pp. 3329-3340 ◽  
Author(s):  
Tara L. Beattie ◽  
Wen Zhou ◽  
Murray O. Robinson ◽  
Lea Harrington
Keyword(s):  
Telomerase Activity ◽  
Amino Terminus ◽  
Telomerase Rna ◽  
Carboxy Terminus ◽  
Active Core ◽  
Human Telomerase ◽  
Precise Role

The minimal, active core of human telomerase is postulated to contain two components, the telomerase RNA hTER and the telomerase reverse transcriptase hTERT. The reconstitution of human telomerase activity in vitro has facilitated the identification of sequences within the telomerase RNA and the RT motifs of hTERT that are essential for telomerase activity. However, the precise role of residues outside the RT domain of hTERT is unknown. Here we have delineated several regions within hTERT that are important for telomerase catalysis, primer use, and interaction with the telomerase RNA and the telomerase-associated protein TEP1. In particular, certain deletions of the amino and carboxy terminus of hTERT that retained an interaction with telomerase RNA and TEP1 were nonetheless completely inactive in vitro and in vivo. Furthermore, hTERT truncations lacking the amino terminus that were competent to bind the telomerase RNA were severely compromised for the ability to elongate telomeric and nontelomeric primers. These results suggest that the interaction of telomerase RNA with hTERT can be functionally uncoupled from polymerization, and that there are regions outside the RT domain of hTERT that are critical for telomerase activity and primer use. These results establish that the human telomerase RT possesses unique polymerization determinants that distinguish it from other RTs.

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