1
|
Zeinoun B, Teixeira MT, Barascu A. TERRA and Telomere Maintenance in the Yeast Saccharomyces cerevisiae. Genes (Basel) 2023; 14:genes14030618. [PMID: 36980890 PMCID: PMC10048448 DOI: 10.3390/genes14030618] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 02/24/2023] [Accepted: 02/26/2023] [Indexed: 03/06/2023] Open
Abstract
Telomeres are structures made of DNA, proteins and RNA found at the ends of eukaryotic linear chromosomes. These dynamic nucleoprotein structures protect chromosomal tips from end-to-end fusions, degradation, activation of damage checkpoints and erroneous DNA repair events. Telomeres were thought to be transcriptionally silent regions because of their constitutive heterochromatin signature until telomeric long non-coding RNAs (LncRNAs) were discovered. One of them, TERRA (TElomeric Repeat-containing RNA), starts in the subtelomeric regions towards the chromosome ends from different telomeres and has been extensively studied in many evolutionarily distant eukaryotes. Changes in TERRA’s expression can lead to telomeric dysfunction, interfere with the replicative machinery and impact telomere length. TERRA also co-localizes in vivo with telomerase, and can form RNA:DNA hybrid structures called R-loops, which have been implicated in the onset of senescence and the alternative lengthening of telomere (ALT) pathway. Yet, the molecular mechanisms involving TERRA, as well as its function, remain elusive. Here, we review the current knowledge of TERRA transcription, structure, expression, regulation and its multiple telomeric and extra-telomeric functions in the budding yeast Saccharomyces cerevisiae.
Collapse
|
2
|
Coutelier H, Ilioaia O, Le Peillet J, Hamon M, D’Amours D, Teixeira MT, Xu Z. The Polo kinase Cdc5 is regulated at multiple levels in the adaptation response to telomere dysfunction. Genetics 2022; 223:6808627. [PMID: 36342193 PMCID: PMC9836022 DOI: 10.1093/genetics/iyac171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 11/02/2022] [Indexed: 11/09/2022] Open
Abstract
Telomere dysfunction activates the DNA damage checkpoint to induce a cell cycle arrest. After an extended period of time, however, cells can bypass the arrest and undergo cell division despite the persistence of the initial damage, a process called adaptation to DNA damage. The Polo kinase Cdc5 in Saccharomyces cerevisiae is essential for adaptation and for many other cell cycle processes. How the regulation of Cdc5 in response to telomere dysfunction relates to adaptation is not clear. Here, we report that Cdc5 protein level decreases after telomere dysfunction in a Mec1-, Rad53- and Ndd1-dependent manner. This regulation of Cdc5 is important to maintain long-term cell cycle arrest but not for the initial checkpoint arrest. We find that both Cdc5 and the adaptation-deficient mutant protein Cdc5-ad are heavily phosphorylated and several phosphorylation sites modulate adaptation efficiency. The PP2A phosphatases are involved in Cdc5-ad phosphorylation status and contribute to adaptation mechanisms. We finally propose that Cdc5 orchestrates multiple cell cycle pathways to promote adaptation.
Collapse
Affiliation(s)
| | | | | | - Marion Hamon
- Sorbonne Université, PSL, CNRS, FR550, Institut de Biologie Physico-Chimique, 75005 Paris, France
| | - Damien D’Amours
- Ottawa Institute of Systems Biology, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Maria Teresa Teixeira
- Sorbonne Université, PSL, CNRS, UMR8226, Institut de Biologie Physico-Chimique, Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, 75005 Paris, France
| | - Zhou Xu
- Corresponding author: Sorbonne Université, CNRS, UMR7238, Institut de Biologie Paris‐Seine, Laboratory of Computational and Quantitative Biology, 75005 Paris, France.
| |
Collapse
|
3
|
Martin H, Doumic M, Teixeira MT, Xu Z. Telomere shortening causes distinct cell division regimes during replicative senescence in Saccharomyces cerevisiae. Cell Biosci 2021; 11:180. [PMID: 34627377 PMCID: PMC8502270 DOI: 10.1186/s13578-021-00693-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Accepted: 09/24/2021] [Indexed: 11/21/2022] Open
Abstract
Background Telomerase-negative cells have limited proliferation potential. In these cells, telomeres shorten until they reach a critical length and induce a permanently arrested state. This process called replicative senescence is associated with genomic instability and participates in tissue and organismal ageing. Experimental data using single-cell approaches in the budding yeast model organism show that telomerase-negative cells often experience abnormally long cell cycles, which can be followed by cell cycles of normal duration, before reaching the terminal senescent state. These series of non-terminal cell cycle arrests contribute to the heterogeneity of senescence and likely magnify its genomic instability. Due to their apparent stochastic nature, investigating the dynamics and the molecular origins of these arrests has been difficult. In particular, whether the non-terminal arrests series stem from a mechanism similar to the one that triggers terminal senescence is not known. Results Here, we provide a mathematical description of sequences of non-terminal arrests to understand how they appear. We take advantage of an experimental data set of cell cycle duration measurements performed in individual telomerase-negative yeast cells that keep track of the number of generations since telomerase inactivation. Using numerical simulations, we show that the occurrence of non-terminal arrests is a generation-dependent process that can be explained by the shortest telomere reaching a probabilistic threshold length. While the onset of senescence is also triggered by telomere shortening, we highlight differences in the laws that describe the number of consecutive arrests in non-terminal arrests compared to senescence arrests, suggesting distinct underlying mechanisms and cellular states. Conclusions Replicative senescence is a complex process that affects cell divisions earlier than anticipated, as exemplified by the frequent occurrence of non-terminal arrests early after telomerase inactivation. The present work unravels two kinetically and mechanistically distinct generation-dependent processes underlying non-terminal and terminal senescence arrests. We suggest that these two processes are responsible for two consequences of senescence at the population level, the increase of genome instability on the one hand, and the limitation of proliferation capacity on the other hand. Supplementary Information The online version contains supplementary material available at 10.1186/s13578-021-00693-3.
Collapse
Affiliation(s)
- Hugo Martin
- JL Lions Laboratory, Sorbonne Université, 75005, Paris, France
| | - Marie Doumic
- JL Lions Laboratory, Sorbonne Université, 75005, Paris, France.
| | - Maria Teresa Teixeira
- Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, Institut de Biologie Physico-Chimique, PSL, CNRS, UMR8226, Sorbonne Université, 75005, Paris, France
| | - Zhou Xu
- Laboratory of Computational and Quantitative Biology, Institut de Biologie Paris-Seine, CNRS, UMR7238, Sorbonne Université, 75005, Paris, France.
| |
Collapse
|
4
|
Abstract
Replicative senescence, which is induced by telomere shortening, underlies the loss of regeneration capacity of organs and is ultimately detrimental to the organism. At the same time, it is required to protect organisms from unlimited cell proliferation that may arise from numerous stimuli or deregulations. One important feature of replicative senescence is its high level of heterogeneity and asynchrony, which promote genome instability and senescence escape. Characterizing this heterogeneity and investigating its sources are thus critical to understanding the robustness of replicative senescence. Here we review the different aspects of senescence driven by telomere attrition that are subject to variation in Saccharomyces cerevisiae, the current understanding of the molecular processes at play, and the consequences of heterogeneity in replicative senescence.
Collapse
Affiliation(s)
- Zhou Xu
- CNRS, UMR7238, Institut de Biologie Paris‐Seine, Laboratory of Computational and Quantitative BiologySorbonne UniversitéParisFrance
| | - Maria Teresa Teixeira
- CNRS, UMR8226, Institut de Biologie Physico‐Chimique, Laboratory of Molecular and Cell Biology of EukaryotesSorbonne Université, PSL Research UniversityParisFrance
| |
Collapse
|
5
|
Eberhard S, Valuchova S, Ravat J, Fulneček J, Jolivet P, Bujaldon S, Lemaire SD, Wollman FA, Teixeira MT, Riha K, Xu Z. Molecular characterization of Chlamydomonas reinhardtii telomeres and telomerase mutants. Life Sci Alliance 2019; 2:2/3/e201900315. [PMID: 31160377 PMCID: PMC6549138 DOI: 10.26508/lsa.201900315] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Revised: 05/27/2019] [Accepted: 05/27/2019] [Indexed: 12/15/2022] Open
Abstract
This study characterizes the sequence, end structure, and length distribution of Chlamydomonas reinhardtii telomeres and shows that telomerase mutants are defective in telomere maintenance. Telomeres are repeated sequences found at the end of the linear chromosomes of most eukaryotes and are required for chromosome integrity. Expression of the reverse-transcriptase telomerase allows for extension of telomeric repeats to counteract natural telomere shortening. Although Chlamydomonas reinhardtii, a photosynthetic unicellular green alga, is widely used as a model organism in photosynthesis and flagella research, and for biotechnological applications, the biology of its telomeres has not been investigated in depth. Here, we show that the C. reinhardtii (TTTTAGGG)n telomeric repeats are mostly nondegenerate and that the telomeres form a protective structure, with a subset ending with a 3′ overhang and another subset presenting a blunt end. Although telomere size and length distributions are stable under various standard growth conditions, they vary substantially between 12 genetically close reference strains. Finally, we identify CrTERT, the gene encoding the catalytic subunit of telomerase and show that telomeres shorten progressively in mutants of this gene. Telomerase mutants eventually enter replicative senescence, demonstrating that telomerase is required for long-term maintenance of telomeres in C. reinhardtii.
Collapse
Affiliation(s)
- Stephan Eberhard
- Sorbonne Université, CNRS, UMR 7141, Institut de Biologie Physico-Chimique, Biologie du Chloroplaste et Perception de la Lumière chez les Micro-algues, Paris, France
| | - Sona Valuchova
- Central European Institute of Technology, Masaryk University, Brno, Czech Republic
| | - Julie Ravat
- Sorbonne Université, CNRS, UMR 7141, Institut de Biologie Physico-Chimique, Biologie du Chloroplaste et Perception de la Lumière chez les Micro-algues, Paris, France
| | - Jaroslav Fulneček
- Central European Institute of Technology, Masaryk University, Brno, Czech Republic
| | - Pascale Jolivet
- Sorbonne Université, PSL Research University, CNRS, UMR 8226, Institut de Biologie Physico-Chimique, Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, Paris, France
| | - Sandrine Bujaldon
- Sorbonne Université, CNRS, UMR 7141, Institut de Biologie Physico-Chimique, Biologie du Chloroplaste et Perception de la Lumière chez les Micro-algues, Paris, France
| | - Stéphane D Lemaire
- Sorbonne Université, PSL Research University, CNRS, UMR 8226, Institut de Biologie Physico-Chimique, Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, Paris, France
| | - Francis-André Wollman
- Sorbonne Université, CNRS, UMR 7141, Institut de Biologie Physico-Chimique, Biologie du Chloroplaste et Perception de la Lumière chez les Micro-algues, Paris, France
| | - Maria Teresa Teixeira
- Sorbonne Université, PSL Research University, CNRS, UMR 8226, Institut de Biologie Physico-Chimique, Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, Paris, France
| | - Karel Riha
- Central European Institute of Technology, Masaryk University, Brno, Czech Republic
| | - Zhou Xu
- Sorbonne Université, PSL Research University, CNRS, UMR 8226, Institut de Biologie Physico-Chimique, Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, Paris, France .,Sorbonne Université, CNRS, UMR 7238, Institut de Biologie Paris-Seine, Laboratory of Computational and Quantitative Biology, Paris, France
| |
Collapse
|
6
|
Coutelier H, Xu Z, Morisse MC, Lhuillier-Akakpo M, Pelet S, Charvin G, Dubrana K, Teixeira MT. Corrigendum: Adaptation to DNA damage checkpoint in senescent telomerase-negative cells promotes genome instability. Genes Dev 2019; 33:378. [PMID: 30824534 DOI: 10.1101/gad.324459.119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
7
|
Jolivet P, Serhal K, Graf M, Eberhard S, Xu Z, Luke B, Teixeira MT. A subtelomeric region affects telomerase-negative replicative senescence in Saccharomyces cerevisiae. Sci Rep 2019; 9:1845. [PMID: 30755624 PMCID: PMC6372760 DOI: 10.1038/s41598-018-38000-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Accepted: 12/04/2018] [Indexed: 11/21/2022] Open
Abstract
In eukaryotes, telomeres determine cell proliferation potential by triggering replicative senescence in the absence of telomerase. In Saccharomyces cerevisiae, senescence is mainly dictated by the first telomere that reaches a critically short length, activating a DNA-damage-like response. How the corresponding signaling is modulated by the telomeric structure and context is largely unknown. Here we investigated how subtelomeric elements of the shortest telomere in a telomerase-negative cell influence the onset of senescence. We found that a 15 kb truncation of the 7L subtelomere widely used in studies of telomere biology affects cell growth when combined with telomerase inactivation. This effect is likely not explained by (i) elimination of sequence homology at chromosome ends that would compromise homology-directed DNA repair mechanisms; (ii) elimination of the conserved subtelomeric X-element; (iii) elimination of a gene that would become essential in the absence of telomerase; and (iv) heterochromatinization of inner genes, causing the silencing of an essential gene in replicative senescent cells. This works contributes to better delineate subtelomere functions and their impact on telomere biology.
Collapse
Affiliation(s)
- Pascale Jolivet
- Sorbonne Université, PSL, CNRS, UMR8226, Institut de Biologie Physico-Chimique, Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, F-75005, Paris, France
| | - Kamar Serhal
- Sorbonne Université, PSL, CNRS, UMR8226, Institut de Biologie Physico-Chimique, Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, F-75005, Paris, France.,Institut de Génétique Humaine, CNRS, Université Montpellier, Montpellier, France
| | - Marco Graf
- Institute of Molecular Biology (IMB), 55128, Mainz, Germany
| | - Stephan Eberhard
- Sorbonne Université, PSL, CNRS, UMR7141, Institut de Biologie Physico-Chimique, Laboratoire de Physiologie Moléculaire et Membranaire du Chloroplaste, F-75005, Paris, France
| | - Zhou Xu
- Sorbonne Université, PSL, CNRS, UMR8226, Institut de Biologie Physico-Chimique, Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, F-75005, Paris, France
| | - Brian Luke
- Institute of Neurobiology and Developmental Biology, JGU Mainz, Ackermannweg 4, 55128, Mainz, Germany.,Institute of Molecular Biology (IMB), 55128, Mainz, Germany
| | - Maria Teresa Teixeira
- Sorbonne Université, PSL, CNRS, UMR8226, Institut de Biologie Physico-Chimique, Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, F-75005, Paris, France.
| |
Collapse
|
8
|
Graf M, Bonetti D, Lockhart A, Serhal K, Kellner V, Maicher A, Jolivet P, Teixeira MT, Luke B. Telomere Length Determines TERRA and R-Loop Regulation through the Cell Cycle. Cell 2017; 170:72-85.e14. [DOI: 10.1016/j.cell.2017.06.006] [Citation(s) in RCA: 128] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Revised: 04/21/2017] [Accepted: 06/06/2017] [Indexed: 10/19/2022]
|
9
|
Soudet J, Jolivet P, Teixeira MT. Elucidation of the DNA end-replication problem in Saccharomyces cerevisiae. Mol Cell 2014; 53:954-64. [PMID: 24656131 DOI: 10.1016/j.molcel.2014.02.030] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Revised: 01/15/2014] [Accepted: 01/31/2014] [Indexed: 11/26/2022]
Abstract
The model for telomere shortening at each replication cycle is currently incomplete, and the exact contribution of the telomeric 3' overhang to the shortening rate remains unclear. Here, we demonstrate key steps of the mechanism of telomere replication in Saccharomyces cerevisiae. By following the dynamics of telomeres during replication at near-nucleotide resolution, we find that the leading-strand synthesis generates blunt-end intermediates before being 5'-resected and filled in. Importantly, the shortening rate is set by positioning the last Okazaki fragments at the very ends of the chromosome. Thus, telomeres shorten in direct proportion to the 3' overhang lengths of 5-10 nucleotides that are present in parental templates. Furthermore, the telomeric protein Cdc13 coordinates leading- and lagging-strand syntheses. Taken together, our data unravel a precise choreography of telomere replication elucidating the DNA end-replication problem and provide a framework to understand the control of the cell proliferation potential.
Collapse
Affiliation(s)
- Julien Soudet
- Centre National de la Recherche Scientifique, UMR8226, Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, Institut de Biologie Physico-Chimique, 75005 Paris, France; Sorbonne Universités, UPMC Univ Paris 06, UMR8226, Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, Institut de Biologie Physico-Chimique, 75005 Paris, France
| | - Pascale Jolivet
- Centre National de la Recherche Scientifique, UMR8226, Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, Institut de Biologie Physico-Chimique, 75005 Paris, France; Sorbonne Universités, UPMC Univ Paris 06, UMR8226, Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, Institut de Biologie Physico-Chimique, 75005 Paris, France
| | - Maria Teresa Teixeira
- Centre National de la Recherche Scientifique, UMR8226, Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, Institut de Biologie Physico-Chimique, 75005 Paris, France; Sorbonne Universités, UPMC Univ Paris 06, UMR8226, Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, Institut de Biologie Physico-Chimique, 75005 Paris, France.
| |
Collapse
|
10
|
Abstract
In the absence of telomerase, telomeres progressively shorten with every round of DNA replication, leading to replicative senescence. In telomerase-deficient Saccharomyces cerevisiae, the shortest telomere triggers the onset of senescence by activating the DNA damage checkpoint and recruiting homologous recombination (HR) factors. Yet, the molecular structures that trigger this checkpoint and the mechanisms of repair have remained elusive. By tracking individual telomeres, we show that telomeres are subjected to different pathways depending on their length. We first demonstrate a progressive accumulation of subtelomeric single-stranded DNA (ssDNA) through 5'-3' resection as telomeres shorten. Thus, exposure of subtelomeric ssDNA could be the signal for cell cycle arrest in senescence. Strikingly, early after loss of telomerase, HR counteracts subtelomeric ssDNA accumulation rather than elongates telomeres. We then asked whether replication repair pathways contribute to this mechanism. We uncovered that Rad5, a DNA helicase/Ubiquitin ligase of the error-free branch of the DNA damage tolerance (DDT) pathway, associates with native telomeres and cooperates with HR in senescent cells. We propose that DDT acts in a length-independent manner, whereas an HR-based repair using the sister chromatid as a template buffers precocious 5'-3' resection at the shortest telomeres.
Collapse
Affiliation(s)
- Emilie Fallet
- Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, Institut de Biologie Physico-Chimique, Centre National de la Recherche Scientifique, Université Pierre et Marie Curie, FRE3354, 75005 Paris, France, Laboratoire de Biologie Moléculaire de la Cellule, Centre National de la Recherche Scientifique, Ecole Normale Supérieure de Lyon, Université de Lyon 1, UMR5239, 69364 Lyon Cedex 07, France, Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen N, Denmark, Institute for Research on Cancer and Aging, Nice (IRCAN), University of Nice Sophia-Antipolis, CNRS UMR7284/INSERM U1081, Faculty of Medicine, Nice F-06107, France and Department of Medical Genetics, CHU Nice, 06202 Nice cedex 3, France
| | | | | | | | | | | |
Collapse
|
11
|
Abstract
Telomeres are multifunctional genetic elements that cap chromosome ends, playing essential roles in genome stability, chromosome higher-order organization and proliferation control. The telomere field has largely benefited from the study of unicellular eukaryotic organisms such as yeasts. Easy cultivation in laboratory conditions and powerful genetics have placed mainly Saccharomyces cerevisiae, Kluveromyces lactis and Schizosaccharomyces pombe as crucial model organisms for telomere biology research. Studies in these species have made it possible to elucidate the basic mechanisms of telomere maintenance, function and evolution. Moreover, comparative genomic analyses show that telomeres have evolved rapidly among yeast species and functional plasticity emerges as one of the driving forces of this evolution. This provides a precious opportunity to further our understanding of telomere biology.
Collapse
Affiliation(s)
- M T Teixeira
- Laboratoire de Biologie Moléculaire de la Cellule of Ecole Normale Supérieure de Lyon, UMR CNRS/INRA/ENS, IFR 128 BioSciences Lyon Gerland, 46 Allée d'Italie, 69364 Lyon cedex 07, France.
| | | |
Collapse
|
12
|
Teixeira MT, Dujon B, Fabre E. Genome-wide nuclear morphology screen identifies novel genes involved in nuclear architecture and gene-silencing in Saccharomyces cerevisiae. J Mol Biol 2002; 321:551-61. [PMID: 12206772 DOI: 10.1016/s0022-2836(02)00652-6] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Organisation of the cell nucleus is crucial for the regulation of gene expression but little is known about how nuclei are structured. To address this issue, we designed a genomic screen to identify factors involved in nuclear architecture in Saccharomyces cerevisiae. This screen is based on microscopic monitoring of nuclear pore complexes and nucleolar proteins fused with the green fluorescent protein in a collection of approximately 400 individual deletion mutants. Among the 12 genes identified by this screen, most affect both the nuclear envelope and the nucleolar morphology. Corresponding gene products are localised preferentially to the nucleus or close to the nuclear periphery. Interestingly, these nuclear morphology alterations were associated with chromatin-silencing defects. These genes provide a molecular context to explore the functional link between nuclear architecture and gene silencing.
Collapse
Affiliation(s)
- Maria Teresa Teixeira
- Département de Structure et Dynamique des Génomes, Unité de Génétique Moléculaire des Levures, URA 2171 CNRS and UFR 927 Univ. P. M Curie, Institut Pasteur, 25 Rue du Docteur Roux, 75724 Cedex 15, Paris, France
| | | | | |
Collapse
|
13
|
Abstract
Nup145p is a component of the nuclear pore complex of Saccharomyces cerevisiae and is essential for mRNA export. Nup145p and its apparent vertebrate homologue are the only known nucleoporins to be composed of two functionally independent peptide moieties resulting from the post-translational cleavage of a large precursor molecule. In this study, the proteolytic cleavage site of Nup145p has been mapped upstream of an evolutionary conserved serine residue. Cleavage occurs at the same site when a precursor is artificially expressed in Escherichia coli. A hydroxyl-containing residue is critical for the reaction, although a thiol-containing residue offers an acceptable replacement. In vitro kinetics experiments using a purified precursor molecule demonstrate that the cleavage is self-catalyzed and that the catalytic domain lies within the N-terminal moiety. Taken altogether, our data are consistent with a proteolytic mechanism involving an N>O acyl rearrangement and a subsequent ester intermediate uncovered in other self-processing proteins.
Collapse
Affiliation(s)
- M T Teixeira
- Unité de Génétique Moléculaire des levures, Institut Pasteur, Département des Biotechnologies, 25 Rue du Docteur Roux, 75724 Paris Cedex 15, France.
| | | | | |
Collapse
|
14
|
Teixeira MT, Siniossoglou S, Podtelejnikov S, Bénichou JC, Mann M, Dujon B, Hurt E, Fabre E. Two functionally distinct domains generated by in vivo cleavage of Nup145p: a novel biogenesis pathway for nucleoporins. EMBO J 1997; 16:5086-97. [PMID: 9305650 PMCID: PMC1170143 DOI: 10.1093/emboj/16.16.5086] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Nup145p is an essential yeast nucleoporin involved in nuclear export of polyadenylated RNAs. We demonstrate here that Nup145p is cleaved in vivo to yield two functionally distinct domains: a carboxy-terminal domain (C-Nup145p) which is located at the nuclear pore complex (NPC) and assembles into the Nup84p complex, and a GLFG-containing amino-terminal domain (N-Nup145p) which is not part of this complex. Whereas the essential C-Nup145p accomplishes the functions required for efficient mRNA export and normal NPC distribution, N-Nup145p, which is homologous to the GLFG-containing nucleoporins Nup100p and Nup116p, is not necessary for cell growth. However, the N-Nup145p becomes essential in a nup188 mutant background. Strikingly, generation of a free N-domain is a prerequisite for complementation of this peculiar synthetic lethal mutant. These data suggest that N- and C-domains of Nup145p perform independent functions, and that the in vivo cleavage observed is of functional importance.
Collapse
Affiliation(s)
- M T Teixeira
- Unité de Génétique Moléculaire des levures (URA 1300 CNRS and UPR 927 Univ. P M Curie), Institut Pasteur, Département des Biotechnologies, Paris, France
| | | | | | | | | | | | | | | |
Collapse
|
15
|
Lessa I, Mendonça GA, Teixeira MT. [Non-communicable chronic diseases in Brazil: from risk factors to social impact]. Bol Oficina Sanit Panam 1996; 120:389-413. [PMID: 8924219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The current epidemiologic profile of Brazil includes both the diseases of underdevelopment and those associated with modern life. Consequently, the country faces the difficult task of carrying out health promotion and protection activities aimed at controlling communicable diseases as well as noncommunicable chronic diseases (NCDs). This study sought to describe the epidemiologic situation of Brazilian adults with regard to NCDs and to present available data on the quality of care provided for these diseases and their social impact. To these ends, a literature review was conducted for the period 1964-1995--that is, since the beginning of the production and dissemination of data on cardiovascular diseases, cancer, and diabetes. Of the 153 bibliographic references that were discovered, 97 were used. The social, political, economic, and health inequities that exist among Brazil's geographic regions are reflected in the national scientific production, which is concentrated in the Southeast and South. Most of the studies based on primary data come from those regions. Information is scarce from the North-east, except the city of Salvador. Therefore, the health profile of adults--including risk factors and morbidity and mortality--can be better delineated for residents of the South and Southeast of the country, whereas for the other regions the necessary information is practically nonexistent. Risk factors linked to life-style are as widespread and important in Brazil as they are in industrialized countries. Prevalence and mortality rates among persons with or without certain socio-environmental risks (such as low level of schooling or unskilled occupations) indicate that NCDs predominate in the lowest social strata. Inter-regional differences in the prevalence of arterial hypertension and diabetes mellitus, the most common fatal cardiovascular causes, and the predominant cancers, as well as morbidity and mortality in both sexes, illustrate the political, social, and economic inequities of development in each region. Comparisons with other countries of the incidence of cardiovascular diseases in a capital in the Northeast or mortality from cardiovascular diseases in the capitals in the South and Southeast show, in the first case, that Salvador has the highest incidence among the Western countries analyzed and, in the second case, that the mortality data rank among the top seven. Cardiovascular diseases and diabetes show increasing trends, with the exception of a small decline for ischemic heart disease and cerebrovascular disease in the municipality of São Paulo. Deaths rates in hospitals from specific cardiovascular diseases and avoidable complications of diabetes are high, especially among indigent patients as opposed to private patients. Premature mortality, as measured by productive years of life lost, reflects the poor quality of medical care and the absence of targeted control programs. These data, combined with other sources of information, such as consents for treatment and pensions paid for illness, give some idea of the impact of NCDs on the society. The authors point to the basic research that could be done in all the country's regions to serve as a basis for planning and implementing populational strategies to reduce risk factors and to treat and control chronic noncommunicable diseases in Brazil.
Collapse
Affiliation(s)
- I Lessa
- Universidade Federal da Bahia, Instituto de Saúde Coletiva, Brasil
| | | | | |
Collapse
|