UniProtKB O77448 TERT record (Tetrahymena thermophila)
Gene Ontology annotation through association of InterPro records with GO terms
Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt
Automatic Gene Ontology annotation based on Rhea mapping
TreeGrafter-generated GO annotations
Combined Automated Annotation using Multiple IEA Methods
Template definition by Tetrahymena telomerase reverse transcriptase.
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An active recombinant Tetrahymena telomerase RNP is minimally TERT plus the telomerase RNA; these are the only two components essential for properly templated activity on oligonucleotide substrates.
"Only two telomerase components are known to be essential for properly templated telomerase activity assayed on oligonucleotide substrates: the telomerase RNA and the telomerase reverse transcriptase (TERT) protein."
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Site-directed mutagenesis of 54 TERT residues showed that TERT residues both within and beyond the RT motifs set the template boundaries and the characteristics of internal template use.
"Our results indicate that TERT contributes directly to RNA template definition and the characteristics of template use."
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The motif A substitution Y623A abolishes discrimination between dNTPs and rNTPs, placing nucleotide selectivity in the TERT active site.
"We conclude that the major qualitative change in activity of the Class 5 enzyme derives from a loss of dNTP/rNTP selectivity."
A telomerase holoenzyme protein enhances telomerase RNA assembly with telomerase reverse transcriptase.
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TERT and TER alone assemble into an active enzyme in rabbit reticulocyte lysate, while p65 is required for the physiological in vivo pathway.
"The telomerase reverse transcriptase (TERT) and telomerase RNA (TER) alone can assemble into active enzyme in a heterologous cell extract"
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p65 and TERT associate only in the presence of TER, so the p65-TERT association within the holoenzyme is RNA-bridged rather than a direct protein-protein contact.
"These findings demonstrate that in the presence of TER, p65 and TERT associate to form a ternary complex."
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p65 does not itself add catalytic activity, since primer extension by TERT-TER was unchanged by p65 coassembly in rabbit reticulocyte lysate.
"Coassembly of p65 did not affect the primer-extension activity of T. thermophila TERT reconstituted with TER in RRL"
Crystal structure of the essential N-terminal domain of telomerase reverse transcriptase.
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Conserved surface residues in a groove of the Tetrahymena TERT TEN domain are required for catalytic activity, and several are required for sequence-specific binding of a single-stranded telomeric DNA primer.
"These residues are crucial for telomerase catalytic activity, and several of them are required for sequence-specific binding of a single-stranded telomeric DNA primer."
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The TEN domain's positively charged C terminus binds RNA non-sequence-specifically and becomes ordered on interaction with other macromolecules.
"The positively charged C terminus, which becomes ordered upon interaction with other macromolecules, is involved in binding RNA in a non-sequence-specific manner."
An RPA-related sequence-specific DNA-binding subunit of telomerase holoenzyme is required for elongation processivity and telomere maintenance.
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Seven Tetrahymena telomerase proteins each copurify active RNP and are each required for telomere maintenance; the p65-TER-TERT catalytic core is joined by a p75-p45-p19 subcomplex and the peripheral p82 and p50 subunits.
"The catalytic core (p65-TER-TERT) is assembled with a three-protein subcomplex (p75-p45-p19) and two peripheral subunits (p82 and p50)."
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High repeat-addition processivity of the holoenzyme, relative to the minimal catalytic RNP, is attributed to DNA-interacting subunits other than TERT and TER.
"DNA-interacting subunits other than telomerase reverse transcriptase (TERT) and telomerase RNA (TER) have been hypothesized to account for high repeat addition processivity of telomerase holoenzyme compared to the minimal catalytic RNP."
Tetrahymena telomerase protein p65 induces conformational changes throughout telomerase RNA (TER) and rescues telomerase reverse transcriptase and TER assembly mutants.
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p65 binding to TER stems I and IV precedes and facilitates TERT binding to TER, defining a hierarchical RNP assembly pathway.
"the binding of p65 to stems I and IV of telomerase RNA (TER) causes a conformational change that facilitates the subsequent binding of telomerase reverse transcriptase (TERT) to TER"
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Within the assembled RNP, p65 mutually stabilises TER and TERT in catalytically active conformations.
"p65 acts as a molecular buttress within the assembled RNP, mutually stabilizing TER and TERT in catalytically active conformations"
The architecture of Tetrahymena telomerase holoenzyme.
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Electron microscopy of the purified holoenzyme places TERT at the centre of the particle, with TERT, TER and p65 forming the RNP catalytic core and p50 acting as a hub to the p75-p19-p45 subcomplex and Teb1.
"Fitting with high-resolution structures reveals the organization of TERT, TER and p65 in the ribonucleoprotein (RNP) catalytic core."
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Eight reciprocally co-purifying, telomerase-specific subunits were established, each essential for telomere length maintenance, of which only TERT, TER and p65 are required for assembly of a catalytically active RNP in vivo.
"Three of these subunits are required for in vivo assembly of a catalytically active RNP: TERT, TER, and the La-family protein p65"
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The TERT TRBD, RT and CTE domains form a ring encircling the active-site cavity.
"The TERT TRBD, RT domain, and C-terminal extension (CTE) form a ring that encircles an active site cavity"
Structure of Tetrahymena telomerase reveals previously unknown subunits, functions, and interactions.
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The cryo-EM structure resolves the TERT-TER-p65 catalytic core and the single-stranded DNA exit path, and maps extensive contacts of the TERT TEN domain with p50 and TEB.
"This study reveals the paths of TER in the TERT-TER-p65 catalytic core and single-stranded DNA exit"
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The accessory modules of Tetrahymena telomerase are RPA and CST paralogs, namely TEB (Teb1-Teb2-Teb3) and p75-p45-p19, rather than shelterin components.
"The p75-p45-p19 subcomplex is identified as another RPA-related complex, CST (CTC1-STN1-TEN1)."