Browsing by Subject "Telomerase"

Now showing 1 - 6 of 6
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    In vivo architecture of the telomerase RNA catalytic core in Trypanosoma brucei.
    (Nucleic acids research, 2021-12) Dey, Abhishek; Monroy-Eklund, Anais; Klotz, Kaitlin; Saha, Arpita; Davis, Justin; Li, Bibo; Laederach, Alain; Chakrabarti, Kausik
    Telomerase is a unique ribonucleoprotein (RNP) reverse transcriptase that utilizes its cognate RNA molecule as a template for telomere DNA repeat synthesis. Telomerase contains the reverse transcriptase protein, TERT and the template RNA, TR, as its core components. The 5'-half of TR forms a highly conserved catalytic core comprising of the template region and adjacent domains necessary for telomere synthesis. However, how telomerase RNA folding takes place in vivo has not been fully understood due to low abundance of the native RNP. Here, using unicellular pathogen Trypanosoma brucei as a model, we reveal important regional folding information of the native telomerase RNA core domains, i.e. TR template, template boundary element, template proximal helix and Helix IV (eCR4-CR5) domain. For this purpose, we uniquely combined in-cell probing with targeted high-throughput RNA sequencing and mutational mapping under three conditions: in vivo (in WT and TERT-/- cells), in an immunopurified catalytically active telomerase RNP complex and ex vivo (deproteinized). We discover that TR forms at least two different conformers with distinct folding topologies in the insect and mammalian developmental stages of T. brucei. Also, TERT does not significantly affect the RNA folding in vivo, suggesting that the telomerase RNA in T. brucei exists in a conformationally preorganized stable structure. Our observed differences in RNA (TR) folding at two distinct developmental stages of T. brucei suggest that important conformational changes are a key component of T. brucei development.
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    Mammalian genes induce partially reprogrammed pluripotent stem cells in non-mammalian vertebrate and invertebrate species.
    (Elife, 2013-09-03) Rosselló, Ricardo Antonio; Chen, Chun-Chun; Dai, Rui; Howard, Jason T; Hochgeschwender, Ute; Jarvis, Erich D
    Cells are fundamental units of life, but little is known about evolution of cell states. Induced pluripotent stem cells (iPSCs) are once differentiated cells that have been re-programmed to an embryonic stem cell-like state, providing a powerful platform for biology and medicine. However, they have been limited to a few mammalian species. Here we found that a set of four mammalian transcription factor genes used to generate iPSCs in mouse and humans can induce a partially reprogrammed pluripotent stem cell (PRPSCs) state in vertebrate and invertebrate model organisms, in mammals, birds, fish, and fly, which span 550 million years from a common ancestor. These findings are one of the first to show cross-lineage stem cell-like induction, and to generate pluripotent-like cells for several of these species with in vivo chimeras. We suggest that the stem-cell state may be highly conserved across a wide phylogenetic range. DOI:http://dx.doi.org/10.7554/eLife.00036.001.
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    Mutations in IDH1, IDH2, and in the TERT promoter define clinically distinct subgroups of adult malignant gliomas.
    (Oncotarget, 2014-03-30) Killela, Patrick J; Pirozzi, Christopher J; Healy, Patrick; Reitman, Zachary J; Lipp, Eric; Rasheed, B Ahmed; Yang, Rui; Diplas, Bill H; Wang, Zhaohui; Greer, Paula K; Zhu, Huishan; Wang, Catherine Y; Carpenter, Austin B; Friedman, Henry; Friedman, Allan H; Keir, Stephen T; He, Jie; He, Yiping; McLendon, Roger E; Herndon, James E; Yan, Hai; Bigner, Darell D
    Frequent mutations in isocitrate dehydrogenase 1 and 2 (IDH1 and IDH2) and the promoter of telomerase reverse transcriptase (TERT) represent two significant discoveries in glioma genomics. Understanding the degree to which these two mutations co-occur or occur exclusively of one another in glioma subtypes presents a unique opportunity to guide glioma classification and prognosis. We analyzed the relationship between overall survival (OS) and the presence of IDH1/2 and TERT promoter mutations in a panel of 473 adult gliomas. We hypothesized and show that genetic signatures capable of distinguishing among several types of gliomas could be established providing clinically relevant information that can serve as an adjunct to histopathological diagnosis. We found that mutations in the TERT promoter occurred in 74.2% of glioblastomas (GBM), but occurred in a minority of Grade II-III astrocytomas (18.2%). In contrast, IDH1/2 mutations were observed in 78.4% of Grade II-III astrocytomas, but were uncommon in primary GBM. In oligodendrogliomas, TERT promoter and IDH1/2 mutations co-occurred in 79% of cases. Patients whose Grade III-IV gliomas exhibit TERT promoter mutations alone predominately have primary GBMs associated with poor median OS (11.5 months). Patients whose Grade III-IV gliomas exhibit IDH1/2 mutations alone predominately have astrocytic morphologies and exhibit a median OS of 57 months while patients whose tumors exhibit both TERT promoter and IDH1/2 mutations predominately exhibit oligodendroglial morphologies and exhibit median OS of 125 months. Analyzing gliomas based on their genetic signatures allows for the stratification of these patients into distinct cohorts, with unique prognosis and survival.
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    Telomerase ribonucleoprotein and genome integrity-An emerging connection in protozoan parasites.
    (Wiley interdisciplinary reviews. RNA, 2022-09) Davis, Justin Alexander; Chakrabarti, Kausik
    Telomerase has an established role in telomere maintenance in eukaryotes. However, recent studies have begun to implicate telomerase in cellular roles beyond telomere maintenance. Specifically, evidence is emerging of cross-talks between telomerase mediated telomere homeostasis and DNA repair pathways. Telomere shortening due to the end replication problem is a constant threat to genome integrity in eukaryotic cells. This poses a particular problem in unicellular parasitic protists because their major virulence genes are located at the subtelomeric loci. Although telomerase is the major regulator of telomere lengthening in eukaryotes, it is less studied in the ancient eukaryotes, including clinically important human pathogens. Recent research is highlighting interplay between telomerase and the DNA damage response in human parasites. The importance of this interplay in pathogen virulence is only beginning to be illuminated, including the potential to highlight novel developmental regulation of telomerase in parasites who transition between multiple developmental stages throughout their life cycle. In this review, we will discuss the telomerase ribonucleoprotein enzyme and DNA repair pathways with emerging views in human parasites to give a broader perspective of the possible connection of telomere, telomerase, and DNA repair pathways across eukaryotic lineages and highlight their potential role in pathogen virulence. This article is categorized under: RNA Structure and Dynamics > Influence of RNA Structure in Biological Systems RNA Evolution and Genomics > RNA and Ribonucleoprotein Evolution RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications.
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    Two-stage genome-wide association study identifies a novel susceptibility locus associated with melanoma.
    (Oncotarget, 2017-03) Ransohoff, Katherine J; Wu, Wenting; Cho, Hyunje G; Chahal, Harvind C; Lin, Yuan; Dai, Hong-Ji; Amos, Christopher I; Lee, Jeffrey E; Tang, Jean Y; Hinds, David A; Han, Jiali; Wei, Qingyi; Sarin, Kavita Y
    Genome-wide association studies have identified 21 susceptibility loci associated with melanoma. These loci implicate genes affecting pigmentation, nevus count, telomere maintenance, and DNA repair in melanoma risk. Here, we report the results of a two-stage genome-wide association study of melanoma. The stage 1 discovery phase consisted of 4,842 self-reported melanoma cases and 286,565 controls of European ancestry from the 23andMe research cohort and the stage 2 replication phase consisted of 1,804 melanoma cases and 1,026 controls from the University of Texas M.D. Anderson Cancer Center. We performed a combined meta-analysis totaling 6,628 melanoma cases and 287,591 controls. Our study replicates 20 of 21 previously known melanoma-loci and confirms the association of the telomerase reverse transcriptase, TERT, with melanoma susceptibility at genome-wide significance. In addition, we uncover a novel polymorphism, rs187843643 (OR = 1.96; 95% CI = [1.54, 2.48]; P = 3.53 x 10-8), associated with melanoma. The SNP rs187842643 lies within a noncoding RNA 177kb downstream of BASP1 (brain associated protein-1). We find that BASP1 expression is suppressed in melanoma as compared with benign nevi, providing additional evidence for a putative role in melanoma pathogenesis.
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    Utility of telomerase-pot1 fusion protein in vascular tissue engineering.
    (Cell Transplant, 2010) Petersen, Thomas H; Hitchcock, Thomas; Muto, Akihito; Calle, Elizabeth A; Zhao, Liping; Gong, Zhaodi; Gui, Liqiong; Dardik, Alan; Bowles, Dawn E; Counter, Christopher M; Niklason, Laura E
    While advances in regenerative medicine and vascular tissue engineering have been substantial in recent years, important stumbling blocks remain. In particular, the limited life span of differentiated cells that are harvested from elderly human donors is an important limitation in many areas of regenerative medicine. Recently, a mutant of the human telomerase reverse transcriptase enzyme (TERT) was described, which is highly processive and elongates telomeres more rapidly than conventional telomerase. This mutant, called pot1-TERT, is a chimeric fusion between the DNA binding protein pot1 and TERT. Because pot1-TERT is highly processive, it is possible that transient delivery of this transgene to cells that are utilized in regenerative medicine applications may elongate telomeres and extend cellular life span while avoiding risks that are associated with retroviral or lentiviral vectors. In the present study, adenoviral delivery of pot1-TERT resulted in transient reconstitution of telomerase activity in human smooth muscle cells, as demonstrated by telomeric repeat amplification protocol (TRAP). In addition, human engineered vessels that were cultured using pot1-TERT-expressing cells had greater collagen content and somewhat better performance in vivo than control grafts. Hence, transient delivery of pot1-TERT to elderly human cells may be useful for increasing cellular life span and improving the functional characteristics of resultant tissue-engineered constructs.