Most cited article - PubMed ID 33050064
Composition and Function of Telomerase-A Polymerase Associated with the Origin of Eukaryotes
Understanding the origin of eukaryotic cells is one of the most difficult problems in all of biology. A key challenge relevant to the question of eukaryogenesis is reconstructing the gene repertoire of the last eukaryotic common ancestor (LECA). As data sets grow, sketching an accurate genomics-informed picture of early eukaryotic cellular complexity requires provision of analytical resources and a commitment to data sharing. Here, we summarise progress towards understanding the biology of LECA and outline a community approach to inferring its wider gene repertoire. Once assembled, a robust LECA gene set will be a useful tool for evaluating alternative hypotheses about the origin of eukaryotes and understanding the evolution of traits in all descendant lineages, with relevance in diverse fields such as cell biology, microbial ecology, biotechnology, agriculture, and medicine. In this Consensus View, we put forth the status quo and an agreed path forward to reconstruct LECA's gene content.
Most eukaryotic organisms employ a telomerase complex for the maintenance of chromosome ends. The core of this complex is composed of telomerase reverse transcriptase (TERT) and telomerase RNA (TR) subunits. The TERT reverse transcriptase (RT) domain synthesises telomeric DNA using the TR template sequence. The other TERT domains contribute to this process in different ways. In particular, the TERT RNA-binding domain (TRBD) interacts with specific TR motif(s). Using a yeast 3-hybrid system, we show the critical role of Arabidopsis thaliana (At) TRBD and embryophyta-conserved KRxR motif in the unstructured linker preceding the TRBD domain for binding to the recently identified AtTR subunit. We also show the essential role of the predicted P4 stem and pseudoknot AtTR structures and provide evidence for the binding of AtTRBD to pseudoknot and KRxR motif stabilising interaction with the P4 stem structure. Our results thus provide the first insight into the core part of the plant telomerase complex.
- Keywords
- A.thaliana telomerase, AtTERT, AtTR, Protein-RNA interactions, Yeast three-hybrid,
- MeSH
- Arabidopsis * genetics enzymology MeSH
- Nucleic Acid Conformation MeSH
- Arabidopsis Proteins * genetics metabolism chemistry MeSH
- RNA, Plant genetics metabolism MeSH
- RNA metabolism genetics MeSH
- Two-Hybrid System Techniques MeSH
- Telomerase * genetics metabolism chemistry MeSH
- Protein Binding MeSH
- Publication type
- Journal Article MeSH
Telomeres are essential structures formed from satellite DNA repeats at the ends of chromosomes in most eukaryotes. Satellite DNA repeat sequences are useful markers for karyotyping, but have a more enigmatic role in the eukaryotic cell. Much work has been done to investigate the structure and arrangement of repetitive DNA elements in classical models with implications for species evolution. Still more is needed until there is a complete picture of the biological function of DNA satellite sequences, particularly when considering non-model organisms. Celebrating Gregor Mendel's anniversary by going to the roots, this review is designed to inspire and aid new research into telomeres and satellites with a particular focus on non-model organisms and accessible experimental and in silico methods that do not require specialized equipment or expensive materials. We describe how to identify telomere (and satellite) repeats giving many examples of published (and some unpublished) data from these techniques to illustrate the principles behind the experiments. We also present advice on how to perform and analyse such experiments, including details of common pitfalls. Our examples are a selection of recent developments and underexplored areas of research from the past. As a nod to Mendel's early work, we use many examples from plants and insects, especially as much recent work has expanded beyond the human and yeast models traditional in telomere research. We give a general introduction to the accepted knowledge of telomere and satellite systems and include references to specialized reviews for the interested reader.
- Keywords
- FISH, NGS, TRAP, eukaryotic tree of life, interstitial telomere sequences, retroelements, satellite, subtelomere structure, telomerase RNA, telomere evolution,
- MeSH
- DNA MeSH
- Humans MeSH
- Repetitive Sequences, Nucleic Acid MeSH
- DNA, Satellite * MeSH
- Base Sequence MeSH
- Telomere * genetics MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Review MeSH
- Names of Substances
- DNA MeSH
- DNA, Satellite * MeSH
Telomerase, an essential enzyme that maintains chromosome ends, is important for genome integrity and organism development. Various hypotheses have been proposed in human, ciliate and yeast systems to explain the coordination of telomerase holoenzyme assembly and the timing of telomerase performance at telomeres during DNA replication or repair. However, a general model is still unclear, especially pathways connecting telomerase with proposed non-telomeric functions. To strengthen our understanding of telomerase function during its intracellular life, we report on interactions of several groups of proteins with the Arabidopsis telomerase protein subunit (AtTERT) and/or a component of telomerase holoenzyme, POT1a protein. Among these are the nucleosome assembly proteins (NAP) and the minichromosome maintenance (MCM) system, which reveal new insights into the telomerase interaction network with links to telomere chromatin assembly and replication. A targeted investigation of 176 candidate proteins demonstrated numerous interactions with nucleolar, transport and ribosomal proteins, as well as molecular chaperones, shedding light on interactions during telomerase biogenesis. We further identified protein domains responsible for binding and analyzed the subcellular localization of these interactions. Moreover, additional interaction networks of NAP proteins and the DOMINO1 protein were identified. Our data support an image of functional telomerase contacts with multiprotein complexes including chromatin remodeling and cell differentiation pathways.
- Keywords
- Arabidopsis, chromatin, folding, mitochondria, protein–protein interaction, replication, telomerase, transport,
- MeSH
- Arabidopsis metabolism MeSH
- Transcription, Genetic MeSH
- Golgi Apparatus metabolism MeSH
- Telomere Homeostasis MeSH
- Protein Interaction Maps MeSH
- Mitochondria metabolism MeSH
- Multiprotein Complexes metabolism MeSH
- Nucleosomes metabolism MeSH
- Peptides metabolism MeSH
- RNA Processing, Post-Transcriptional genetics MeSH
- Arabidopsis Proteins chemistry metabolism MeSH
- Telomere-Binding Proteins metabolism MeSH
- Gene Expression Regulation, Plant MeSH
- DNA Replication MeSH
- Chromatin Assembly and Disassembly MeSH
- Ribosomes metabolism MeSH
- Telomerase metabolism MeSH
- Protein Binding MeSH
- Publication type
- Journal Article MeSH
- Names of Substances
- Multiprotein Complexes MeSH
- Nucleosomes MeSH
- Peptides MeSH
- Arabidopsis Proteins MeSH
- Telomere-Binding Proteins MeSH
- Telomerase MeSH
Telomerase RNA (TR) carries the template for synthesis of telomere DNA and provides a scaffold for telomerase assembly. Fungal TRs are long and have been compared to higher eukaryotes, where they show considerable diversity within phylogenetically close groups. TRs of several Saccharomycetaceae were recently identified, however, many of these remained uncharacterised in the template region. Here we show that this is mainly due to high variability in telomere sequence. We predicted the telomere sequences using Tandem Repeats Finder and then we identified corresponding putative template regions in TR candidates. Remarkably long telomere units and the corresponding putative TRs were found in Tetrapisispora species. Notably, variable lengths of the annealing sequence of the template region (1-10 nt) were found. Consequently, species with the same telomere sequence may not harbour identical TR templates. Thus, TR sequence alone can be used to predict a template region and telomere sequence, but not to determine these exactly. A conserved feature of telomere sequences, tracts of adjacent Gs, led us to test the propensity of individual telomere sequences to form G4. The results show highly diverse values of G4-propensity, indicating the lack of ubiquitous conservation of this feature across Saccharomycetaceae.
- MeSH
- Benzothiazoles metabolism MeSH
- Fluorescence MeSH
- G-Quadruplexes MeSH
- Genetic Variation * MeSH
- Templates, Genetic * MeSH
- Reproducibility of Results MeSH
- RNA genetics MeSH
- Saccharomycetales genetics MeSH
- Base Sequence MeSH
- Telomerase genetics MeSH
- Telomere genetics MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Names of Substances
- Benzothiazoles MeSH
- RNA MeSH
- Telomerase MeSH
- telomerase RNA MeSH Browser
- thioflavin T MeSH Browser
