Structures of telomerase at several steps of telomere repeat synthesis

He, Yao; Wang, Yaqiang; Liu, Baocheng; Helmling, Christina; Sušac, Lukas; Cheng, Ryan R.; Zh, Zhou; Feigon, Juli

doi:10.1038/s41586-021-03529-9

Cited by 49 publications

(44 citation statements)

References 71 publications

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“…Notably, the dynamic movement of fingers-B has also been proposed to play an important role in T. thermophila telomerase action. 28 However, in contrast to our seesaw-like movement of fingers-B in each step of nucleotide addition of human telomerase, the T. thermophila telomerase study proposed that fingers-B is only in the open state to allow RNA template translocation at the end of the telomere extension cycle. 28 Future studies are needed to investigate and verify these two models.…”

Section: Resultsmentioning

confidence: 67%

“…S11b ). 28 , 29 , 49 Similar to human TERT Leu980 , these non-glycine zipper head residues very likely also limit the length of the primer–template duplex in the active site and facilitate RAP during repetitive telomere extension. Therefore, we propose an evolutionally conserved zipper head mechanism for all eukaryotic telomerases in which a non-glycine residue, not its amino acid identity at the zipper head position of TERT, is essential for the repetitive telomere extension.…”

Section: Resultsmentioning

confidence: 99%

“…Similar to our structure, a short primer–template duplex in the active site was also observed in the recent structures of human and T. thermophila telomerases. 28 , 29 A bridge loop in T. thermophila TERT RBD was proposed to help maintain this short duplex through a stacking interaction between TERT Phe414 and product nucleotides at positions 5–8 that flip away from the duplex. 28 We propose that the zipper head residue Asn926 in T. thermophila telomerase plays a major role in limiting the duplex length to separate the template from the primer strand beyond position 4, and the latter is then stabilized by the bridge loop.…”

Section: Resultsmentioning

confidence: 99%

“… 28 , 29 A bridge loop in T. thermophila TERT RBD was proposed to help maintain this short duplex through a stacking interaction between TERT Phe414 and product nucleotides at positions 5–8 that flip away from the duplex. 28 We propose that the zipper head residue Asn926 in T. thermophila telomerase plays a major role in limiting the duplex length to separate the template from the primer strand beyond position 4, and the latter is then stabilized by the bridge loop. Structural comparison revealed a corresponding bridge loop in our and the recently reported human telomerase structures (Supplementary information, Fig.…”

Section: Resultsmentioning

confidence: 99%

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Zipper head mechanism of telomere synthesis by human telomerase

et al. 2021

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Telomerase, a multi-subunit ribonucleoprotein complex, is a unique reverse transcriptase that catalyzes the processive addition of a repeat sequence to extend the telomere end using a short fragment of its own RNA component as the template. Despite recent structural characterizations of human and Tetrahymena telomerase, it is still a mystery how telomerase repeatedly uses its RNA template to synthesize telomeric DNA. Here, we report the cryo-EM structure of human telomerase holoenzyme bound with telomeric DNA at resolutions of 3.5 Å and 3.9 Å for the catalytic core and biogenesis module, respectively. The structure reveals that a leucine residue Leu980 in telomerase reverse transcriptase (TERT) catalytic subunit functions as a zipper head to limit the length of the short primer–template duplex in the active center. Moreover, our structural and computational analyses suggest that TERT and telomerase RNA (hTR) are organized to harbor a preformed active site that can accommodate short primer–template duplex substrates for catalysis. Furthermore, our findings unveil a double-fingers architecture in TERT that ensures nucleotide addition processivity of human telomerase. We propose that the zipper head Leu980 is a structural determinant for the sequence-based pausing signal of DNA synthesis that coincides with the RNA element-based physical template boundary. Functional analyses unveil that the non-glycine zipper head plays an essential role in both telomerase repeat addition processivity and telomere length homeostasis. In addition, we also demonstrate that this zipper head mechanism is conserved in all eukaryotic telomerases. Together, our study provides an integrated model for telomerase-mediated telomere synthesis.

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Section: Resultsmentioning

confidence: 67%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Zipper head mechanism of telomere synthesis by human telomerase

et al. 2021

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“…How do G-quadruplexes affect telomerase activity [ 93 ]? Although structures of Tetrahymena telomerase at different stages of the catalytic cycle have been recently captured [ 94 ], the human enzyme will require its own sets of snapshots for a thorough mechanistic understanding of its catalytic actions.…”

Section: Prospectsmentioning

confidence: 99%

Structural biology of human telomerase: progress and prospects

Nguyen

2021

Biochemical Society Transactions

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Telomerase ribonucleoprotein was discovered over three decades ago as a specialized reverse transcriptase that adds telomeric repeats to the ends of linear eukaryotic chromosomes. Telomerase plays key roles in maintaining genome stability; and its dysfunction and misregulation have been linked to different types of cancers and a spectrum of human genetic disorders. Over the years, a wealth of genetic and biochemical studies of human telomerase have illuminated its numerous fascinating features. Yet, structural studies of human telomerase have lagged behind due to various challenges. Recent technical developments in cryo-electron microscopy have allowed for the first detailed visualization of the human telomerase holoenzyme, revealing unprecedented insights into its active site and assembly. This review summarizes the cumulative work leading to the recent structural advances, as well as highlights how the future structural work will further advance our understanding of this enzyme.

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Tetrahymena

Cole¹

2022

Encyclopedia of Life Sciences

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The Tetrahymena genus is composed of mostly free‐living ciliated protozoa that have helped researchers gain insight into fundamental problems of cell biology. As all ciliates, Tetrahymena contain separate germline and somatic nuclei known as the micronucleus and macronucleus, respectively. The macronucleus is derived from a copy of the micronucleus through a process that involves extensive whole‐genome rearrangement and that is under intensive study. Tetrahymena thermophila can be readily manipulated using the tools of genetics, molecular biology, cell biology and biochemistry. Recently, next‐generation, whole‐genome sequencing has made possible the identification of previously unidentified genes responsible for a rich gallery of mutant phenotypes. Notable discoveries made using Tetrahymena include the structure of telomeres and telomerase, self‐splicing RNA, the first microtubular motor, and the link between histone acetylation and gene regulation. The approximately 104 Megabase macronuclear genome of T. thermophila has been sequenced and annotated; the micronuclear genome has been sequenced as well. Key Concepts Tetrahymena are large, complex eukaryotic cells well‐suited both for university research and for the undergraduate teaching‐laboratory. Tetrahymena, have been studied for nearly a century and have been the source of numerous ground‐breaking discoveries. Applying modern tools of genomics, proteomics, and next‐generation, whole‐genome sequencing has ushered in a new era of research to such topics as the assembly of basal bodies and cilia, pattern formation, novel roles for small ribonucleic acids ( RNAs ), membrane trafficking, secretion, phagocytosis, pinocytosis, cytoskeletal motility and chromosome dynamics including studies on the origins of deoxyribonucleic acid ( DNA ) replication, telomere synthesis, meiosis, recombination, apoptosis and the regulation of gene expression through epigenetic chromatin marking. Tetrahymena offer special insights into cell biological processes due to their many original and extraordinary capabilities including the use of a unique genetic code, novel twists on metabolism and protein trafficking, self‐splicing RNA, programmed genome rearrangement involved in genome surveillance, cortical patterning and cellular regeneration. Tetrahymena exhibit both conserved and evolutionarily divergent solutions to fundamental cell biological problems.

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Structures of telomerase at several steps of telomere repeat synthesis

Cited by 49 publications

References 71 publications

Zipper head mechanism of telomere synthesis by human telomerase

Zipper head mechanism of telomere synthesis by human telomerase

Structural biology of human telomerase: progress and prospects

Tetrahymena

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