Telomerase-Mediated Anti-Ageing Interventions.

The ageing process involves a gradual decline of chromosome integrity throughout an organism's lifespan. Telomeres are protective DNA-protein complexes that cap the ends of linear chromosomes in eukaryotic organisms. Telomeric DNA consists of long stretches of short "TTAGGG" repeats that are conserved across most eukaryotes including humans.

Transposition, duplication, and divergence of the telomerase RNA underlies the evolution of telomeres.

Telomeres are nucleoprotein complexes with a crucial role of protecting chromosome ends. It consists of simple repeat sequences and dedicated telomere-binding proteins. Because of its vital functions, components of the telomere, for example its sequence, should be under strong evolutionary constraint.

Room-temperature structural studies of SARS-CoV-2 protein NendoU with an X-ray free-electron laser.

NendoU from SARS-CoV-2 is responsible for the virus's ability to evade the innate immune system by cleaving the polyuridine leader sequence of antisense viral RNA. Here we report the room-temperature structure of NendoU, solved by serial femtosecond crystallography at an X-ray free-electron laser to 2.6 Å resolution.

Biogenesis of telomerase RNA from a protein-coding mRNA precursor.

Telomerase is a eukaryotic ribonucleoprotein (RNP) enzyme that adds DNA repeats onto chromosome ends to maintain genomic stability and confer cellular immortality in cancer and stem cells. The telomerase RNA (TER) component is essential for telomerase catalytic activity and provides the template for telomeric DNA synthesis. The biogenesis of TERs is extremely divergent across eukaryotic kingdoms, employing distinct types of transcription machinery and processing pathways.

Plant telomere biology: The green solution to the end-replication problem.

Telomere maintenance is a fundamental cellular process conserved across all eukaryotic lineages. Although plants and animals diverged over 1.5 billion years ago, lessons learned from plants continue to push the boundaries of science, revealing detailed molecular mechanisms in telomere biology with broad implications for human health, aging biology, and stress responses.

Monophyletic Origin and Divergent Evolution of Animal Telomerase RNA.

Telomerase RNA (TR) is a noncoding RNA essential for the function of telomerase ribonucleoprotein. TRs from vertebrates, fungi, ciliates, and plants exhibit extreme diversity in size, sequence, secondary structure, and biogenesis pathway. However, the evolutionary pathways leading to such unusual diversity among eukaryotic kingdoms remain elusive.

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

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.

A single nucleotide incorporation step limits human telomerase repeat addition activity.

Human telomerase synthesizes telomeric DNA repeats (GGTTAG) onto chromosome ends using a short template from its integral telomerase RNA (hTR). However, telomerase is markedly slow for processive DNA synthesis among DNA polymerases. We report here that the unique template-embedded pause signal restricts the first nucleotide incorporation for each repeat synthesized, imparting a significantly greater This slow nucleotide incorporation step drastically limits repeat addition processivity and rate under physiological conditions, which is alleviated with augmented concentrations of dGTP or dGDP, and not with dGMP nor other nucleotides.

Telomere biology and telomerase mutations in cirrhotic patients with hepatocellular carcinoma.

Telomeres are repetitive DNA sequences at linear chromosome termini, protecting chromosomes against end-to-end fusion and damage, providing chromosomal stability. Telomeres shorten with mitotic cellular division, but are maintained in cells with high proliferative capacity by telomerase. Loss-of-function mutations in telomere-maintenance genes are genetic risk factors for cirrhosis development in humans and murine models.

In Vitro Preparation and Crystallization of Vertebrate Telomerase Subunits.

Telomerase is a unique reverse transcriptase that replicates the telomeric DNA at most eukaryotic chromosomal ends. The telomerase consists of the catalytic protein subunit TERT and the RNA component TR that provides the template for telomeric DNA synthesis. In vitro reconstitution of telomerase core components in large quantity is the prerequisite to studying the catalytic mechanisms of telomerase at the structural level; however, large-scale preparation of recombinant telomerase, especially that of higher eukaryotes, has been a big challenge for a long time.

The functional requirement of two structural domains within telomerase RNA emerged early in eukaryotes.

Telomerase emerged during evolution as a prominent solution to the eukaryotic linear chromosome end-replication problem. Telomerase minimally comprises the catalytic telomerase reverse transcriptase (TERT) and telomerase RNA (TR) that provides the template for telomeric DNA synthesis. While the TERT protein is well-conserved across taxa, TR is highly divergent amongst distinct groups of species.

Evolutionary perspectives of telomerase RNA structure and function.

Telomerase is the eukaryotic solution to the 'end-replication problem' of linear chromosomes by synthesising the highly repetitive DNA constituent of telomeres, the nucleoprotein cap that protects chromosome termini. Functioning as a ribonucleoprotein (RNP) enzyme, telomerase is minimally composed of the highly conserved catalytic telomerase reverse transcriptase (TERT) and essential telomerase RNA (TR) component. Beyond merely providing the template for telomeric DNA synthesis, TR is an innate telomerase component and directly facilitates enzymatic function.

Structure and function of echinoderm telomerase RNA.

Telomerase is a ribonucleoprotein (RNP) enzyme that requires an integral telomerase RNA (TR) subunit, in addition to the catalytic telomerase reverse transcriptase (TERT), for enzymatic function. The secondary structures of TRs from the three major groups of species, ciliates, fungi, and vertebrates, have been studied extensively and demonstrate dramatic diversity. Herein, we report the first comprehensive secondary structure of TR from echinoderms-marine invertebrates closely related to vertebrates-determined by phylogenetic comparative analysis of 16 TR sequences from three separate echinoderm classes.

Sample Preparation of Telomerase Subunits for Crystallization.

Telomerase is a large ribonucleoprotein complex that replicates the linear chromosome ends in most eukaryotes. Large-scale preparation of the telomerase core components has long been a big challenge in this field, hindering the understanding of the catalytic mechanism of telomerase, as well as slowing down the development of telomerase inhibitors for cancer therapy. We have successfully developed a protocol for large-scale preparation of the TRBD-CR4/5 complex of the medaka telomerase , and used this method to study the high-resolution structure of the TRBD-CR4/5 complex by X-ray crystallography.

Prevalent and distinct spliceosomal 3'-end processing mechanisms for fungal telomerase RNA.

Telomerase RNA (TER) is an essential component of the telomerase ribonucleoprotein complex. The mechanism for TER 3'-end processing is highly divergent among different organisms. Here we report a unique spliceosome-mediated TER 3'-end cleavage mechanism in Neurospora crassa that is distinct from that found specifically in the fission yeast Schizosaccharomyces pombe.

Telomerase mutations in smokers with severe emphysema.

Mutations in the essential telomerase genes TERT and TR cause familial pulmonary fibrosis; however, in telomerase-null mice, short telomeres predispose to emphysema after chronic cigarette smoke exposure. Here, we tested whether telomerase mutations are a risk factor for human emphysema by examining their frequency in smokers with chronic obstructive pulmonary disease (COPD). Across two independent cohorts, we found 3 of 292 severe COPD cases carried deleterious mutations in TERT (1%).

A self-regulating template in human telomerase.

Telomerase is a specialized reverse transcriptase (RT) containing an intrinsic telomerase RNA (TR) component. It synthesizes telomeric DNA repeats, (GGTTAG)n in humans, by reiteratively copying a precisely defined, short template sequence from the integral TR. The specific mechanism of how the telomerase active site uses this short template region accurately and efficiently during processive DNA repeat synthesis has remained elusive.

Structural basis for protein-RNA recognition in telomerase.

Telomerase is a large ribonucleoprotein complex minimally composed of a catalytic telomerase reverse transcriptase (TERT) and an RNA component (TR) that provides the template for telomeric DNA synthesis. However, it remains unclear how TERT and TR assemble into a functional telomerase. Here we report the crystal structure of the conserved regions 4 and 5 (CR4/5) of TR in complex with the TR-binding domain (TRBD) of TERT from the teleost fish Oryzias latipes.

Identification of purple sea urchin telomerase RNA using a next-generation sequencing based approach.

Telomerase is a ribonucleoprotein (RNP) enzyme essential for telomere maintenance and chromosome stability. While the catalytic telomerase reverse transcriptase (TERT) protein is well conserved across eukaryotes, telomerase RNA (TR) is extensively divergent in size, sequence, and structure. This diversity prohibits TR identification from many important organisms.

A homozygous telomerase T-motif variant resulting in markedly reduced repeat addition processivity in siblings with Hoyeraal Hreidarsson syndrome.

Hoyeraal Hreidarsson syndrome (HHS) is a form of dyskeratosis congenita (DC) characterized by bone marrow failure, intrauterine growth retardation, developmental delay, microcephaly, cerebellar hypoplasia, immunodeficiency, and extremely short telomeres. As with DC, mutations in genes encoding factors required for telomere maintenance, such as telomerase reverse transcriptase (TERT), have been found in patients with HHS. We describe 2 sibling HHS cases caused by a homozygous mutation (p.

The common ancestral core of vertebrate and fungal telomerase RNAs.

Telomerase is a ribonucleoprotein with an intrinsic telomerase RNA (TER) component. Within yeasts, TER is remarkably large and presents little similarity in secondary structure to vertebrate or ciliate TERs. To better understand the evolution of fungal telomerase, we identified 74 TERs from Pezizomycotina and Taphrinomycotina subphyla, sister clades to budding yeasts.

RNA-protein binding interface in the telomerase ribonucleoprotein.

Telomerase is a specialized reverse transcriptase containing an intrinsic telomerase RNA (TR) which provides the template for telomeric DNA synthesis. Distinct from conventional reverse transcriptases, telomerase has evolved a unique TR-binding domain (TRBD) in the catalytic telomerase reverse transcriptase (TERT) protein, integral for ribonucleoprotein assembly. Two structural elements in the vertebrate TR, the pseudoknot and CR4/5, bind TERT independently and are essential for telomerase enzymatic activity.

It all comes together at the ends: telomerase structure, function, and biogenesis.

Telomerase is a reverse transcriptase specialized in the addition of telomeric DNA repeats onto the ends of chromosomes. Telomere extension offsets the loss of telomeric repeats from the failure of DNA polymerases to fully replicate linear chromosome ends. Telomerase functions as a ribonucleoprotein, requiring an integral telomerase RNA (TR) component, in addition to the catalytic telomerase reverse transcriptase (TERT).

RNA/DNA hybrid binding affinity determines telomerase template-translocation efficiency.

Telomerase synthesizes telomeric DNA repeats onto chromosome termini from an intrinsic RNA template. The processive synthesis of DNA repeats relies on a unique, yet poorly understood, mechanism whereby the telomerase RNA template translocates and realigns with the DNA primer after synthesizing each repeat. Here, we provide evidence that binding of the realigned RNA/DNA hybrid by the active site is an essential step for template translocation.

Ancestral mutation in telomerase causes defects in repeat addition processivity and manifests as familial pulmonary fibrosis.

The telomerase reverse transcriptase synthesizes new telomeres onto chromosome ends by copying from a short template within its integral RNA component. During telomere synthesis, telomerase adds multiple short DNA repeats successively, a property known as repeat addition processivity. However, the consequences of defects in processivity on telomere length maintenance are not fully known.