scholarly journals A putative cap binding protein and the methyl phosphate capping enzyme Bin3/MePCE function in telomerase biogenesis.

2021 ◽  
Author(s):  
Diego J Paez-Moscoso ◽  
David V Ho ◽  
Lili Pan ◽  
Katie Hildebrand ◽  
Kristi L Jensen ◽  
...  
Keyword(s):  
Affinity Purification ◽  
Structural Similarity ◽  
Telomerase Activity ◽  
Telomerase Rna ◽  
Complex Assembly ◽  
Ribonucleoprotein Complex ◽  
The Core ◽  
Capping Enzyme ◽  
Cap Binding Complex ◽  
Methyl Phosphate

Telomerase reverse transcriptase (TERT) and the noncoding telomerase RNA (TR) subunit constitute the core of telomerase. Additional subunits are required for ribonucleoprotein complex assembly and in some cases remain stably associated with the active holoenzyme. Pof8, a member of the LARP7 protein family is such a constitutive component of telomerase in fission yeast. Using affinity purification of Pof8, we have identified two previously uncharacterized proteins that form a complex with Pof8 and participate in telomerase biogenesis. Both proteins participate in ribonucleoprotein complex assembly and are required for wildtype telomerase activity and telomere length maintenance. One factor we named Thc1 (Telomerase Holoenzyme Component 1) shares structural similarity with the nuclear cap binding complex and the poly-adenosine ribonuclease (PARN), the other is the ortholog of the methyl phosphate capping enzyme (Bin3/MePCE) in metazoans and was named Bmc1 (Bin3/MePCE 1) to reflect its evolutionary roots. Thc1 and Bmc1 function together with Pof8 in recognizing correctly folded telomerase RNA and promoting the recruitment of the Lsm2-8 complex and the catalytic subunit to assemble functional telomerase.

scholarly journals Comprehensive Structure-Function Analysis of the Core Domain of Human Telomerase RNA

2003 ◽  
Vol 23 (19) ◽  
pp. 6849-6856 ◽  
Author(s):  
Hinh Ly ◽  
Elizabeth H. Blackburn ◽  
Tristram G. Parslow
Keyword(s):  
Mutational Analysis ◽  
Function Analysis ◽  
Telomerase Activity ◽  
Telomerase Rna ◽  
Dna Repeats ◽  
Telomeric Dna ◽  
Core Domain ◽  
The Core ◽  
Optimal Function ◽  
Human Telomerase

ABSTRACT Telomerase is a cellular reverse transcriptase that uses part of its integral RNA (called TER) as the template to synthesize telomeric DNA repeats. Vertebrate TERs are thought to share a conserved, highly structured core domain that includes the templating sequence and a pseudoknot, but not all features of the predicted core structure have been verified directly or shown to affect telomerase enzymatic activity. Here, we report a systematic mutational analysis of the core domain (residues 1 to 210) of human telomerase RNA (hTER). Our data confirm that optimal hTER activity requires the integrity of four short helices (P2a.1, P2a, P2b, and P3) which create the proposed pseudoknot and that features of both the primary sequence and secondary structure in P2b and P3 contribute to optimal function. At least part of the long-range P1 pairing is also required, despite the lack of a known P1 counterpart in rodent TERs. Among the predicted single-stranded regions, we found that J2b/3, portions of J2a/3, and residues in and around the template make sequence-specific contributions to telomerase function. Additionally, we provide evidence that naturally occurring hTER sequence polymorphisms found in some patients with aplastic anemia can inhibit telomerase activity by disrupting critical structures within the hTER core domain.

scholarly journals Telomerase activation in mouse mammary tumors: lack of detectable telomere shortening and evidence for regulation of telomerase RNA with cell proliferation.

1996 ◽  
Vol 16 (7) ◽  
pp. 3765-3772 ◽  
Author(s):  
D Broccoli ◽  
L A Godley ◽  
L A Donehower ◽  
H E Varmus ◽  
T de Lange
Keyword(s):  
Cell Proliferation ◽  
Tumor Development ◽  
Mammary Tumorigenesis ◽  
Mammary Tumors ◽  
Mammary Glands ◽  
Telomerase Activity ◽  
Telomerase Rna ◽  
Proliferating Cells ◽  
Telomere Shortening ◽  
Mouse Mammary Tumors

Activation of telomerase in human cancers is thought to be necessary to overcome the progressive loss of telomeric DNA that accompanies proliferation of normal somatic cells. According to this model, telomerase provides a growth advantage to cells in which extensive terminal sequence loss threatens viability. To test these ideas, we have examined telomere dynamics and telomerase activation during mammary tumorigenesis in mice carrying a mouse mammary tumor virus long terminal repeat-driven Wnt-1 transgene. We also analyzed Wnt-1-induced mammary tumors in mice lacking p53 function. Normal mammary glands, hyperplastic mammary glands, and mammary carcinomas all had the long telomeres (20 to 50 kb) typical of Mus musculus and did not show telomere shortening during tumor development. Nevertheless, telomerase activity and the RNA component of the enzyme were consistently upregulated in Wnt-1-induced mammary tumors compared with normal and hyperplastic tissues. The upregulation of telomerase activity and RNA also occurred during tumorigenesis in p53-deficient mice. The expression of telomerase RNA correlated strongly with histone H4 mRNA in all normal tissues and tumors, indicating that the RNA component of telomerase is regulated with cell proliferation. Telomerase activity in the tumors was elevated to a greater extent than telomerase RNA, implying that the enzymatic activity of telomerase is regulated at additional levels. Our data suggest that the mechanism of telomerase activation in mouse mammary tumors is not linked to global loss of telomere function but involves multiple regulatory events including upregulation of telomerase RNA in proliferating cells.

Expression of Telomerase RNA, Telomerase Activity, and Telomere Length in Human Gliomas

1997 ◽  
Vol 239 (3) ◽  
pp. 830-834 ◽  
Author(s):  
Ken Morii ◽  
Ryuichi Tanaka ◽  
Kiyoshi Onda ◽  
Itaru Tsumanuma ◽  
Jyunichi Yoshimura
Keyword(s):  
Telomere Length ◽  
Telomerase Activity ◽  
Telomerase Rna ◽  
Human Gliomas

scholarly journals Sec1p Binds to SNARE Complexes and Concentrates at Sites of Secretion

1999 ◽  
Vol 146 (2) ◽  
pp. 333-344 ◽  
Author(s):  
Chavela M. Carr ◽  
Eric Grote ◽  
Mary Munson ◽  
Frederick M. Hughson ◽  
Peter J. Novick
Keyword(s):  
Fluorescent Protein ◽  
Snare Complex ◽  
The Other ◽  
Complex Assembly ◽  
Vesicle Docking ◽  
Neuronal Protein ◽  
The Core ◽  
Target Membrane ◽  
Green Fluorescent ◽  
And Function

Proteins of the Sec1 family have been shown to interact with target-membrane t-SNAREs that are homologous to the neuronal protein syntaxin. We demonstrate that yeast Sec1p coprecipitates not only the syntaxin homologue Ssop, but also the other two exocytic SNAREs (Sec9p and Sncp) in amounts and in proportions characteristic of SNARE complexes in yeast lysates. The interaction between Sec1p and Ssop is limited by the abundance of SNARE complexes present in sec mutants that are defective in either SNARE complex assembly or disassembly. Furthermore, the localization of green fluorescent protein (GFP)-tagged Sec1p coincides with sites of vesicle docking and fusion where SNARE complexes are believed to assemble and function. The proposal that SNARE complexes act as receptors for Sec1p is supported by the mislocalization of GFP-Sec1p in a mutant defective for SNARE complex assembly and by the robust localization of GFP-Sec1p in a mutant that fails to disassemble SNARE complexes. The results presented here place yeast Sec1p at the core of the exocytic fusion machinery, bound to SNARE complexes and localized to sites of secretion.

scholarly journals Telomerase Activity Reconstitutedin Vitrowith Purified Human Telomerase Reverse Transcriptase and Human Telomerase RNA Component

2000 ◽  
Vol 275 (29) ◽  
pp. 22568-22573 ◽  
Author(s):  
Kenkichi Masutomi ◽  
Shuichi Kaneko ◽  
Naoyuki Hayashi ◽  
Tatsuya Yamashita ◽  
Yukihiro Shirota ◽  
...  
Keyword(s):  
Reverse Transcriptase ◽  
Telomerase Activity ◽  
Telomerase Reverse Transcriptase ◽  
Telomerase Rna ◽  
Human Telomerase Reverse Transcriptase ◽  
Human Telomerase

scholarly journals Telomerase biogenesis requires a novel Mex67 function and a cytoplasmic association with the Sm7 complex

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Yulia Vasianovich ◽  
Emmanuel Bajon ◽  
Raymund J Wellinger
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Life Cycle ◽  
Reverse Transcriptase ◽  
Nuclear Export ◽  
Complex Life Cycle ◽  
Telomerase Reverse Transcriptase ◽  
Telomerase Rna ◽  
The Core ◽  
Nuclear Stability

The templating RNA is the core of the telomerase reverse transcriptase. In Saccharomyces cerevisiae, the complex life cycle and maturation of telomerase includes a cytoplasmic stage. However, timing and reason for this cytoplasmic passage are poorly understood. Here, we use inducible RNA tagging experiments to show that immediately after transcription, newly synthesized telomerase RNAs undergo one round of nucleo-cytoplasmic shuttling. Their export depends entirely on Crm1/Xpo1, whereas re-import is mediated by Kap122 plus redundant, kinetically less efficient import pathways. Strikingly, Mex67 is essential to stabilize newly transcribed RNA before Xpo1-mediated nuclear export. The results further show that the Sm7 complex associates with and stabilizes the telomerase RNA in the cytoplasm and promotes its nuclear re-import. Remarkably, after this cytoplasmic passage, the nuclear stability of telomerase RNA no longer depends on Mex67. These results underscore the utility of inducible RNA tagging and challenge current models of telomerase maturation.

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.

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