Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 30
Filtrar
1.
EMBO Rep ; 17(5): 753-68, 2016 05.
Artículo en Inglés | MEDLINE | ID: mdl-26902262

RESUMEN

Retrotransposons, the ancestors of retroviruses, have the potential for gene disruption and genomic takeover if not kept in check. Paradoxically, although host cells repress these elements by multiple mechanisms, they are transcribed and are even activated under stress conditions. Here, we describe a new mechanism of retrotransposon regulation through transcription start site (TSS) selection by altered nucleosome occupancy. We show that Fun30 chromatin remodelers cooperate to maintain a high level of nucleosome occupancy at retrotransposon-flanking long terminal repeat (LTR) elements. This enforces the use of a downstream TSS and the production of a truncated RNA incapable of reverse transcription and retrotransposition. However, in stressed cells, nucleosome occupancy at LTR elements is reduced, and the TSS shifts to allow for productive transcription. We propose that controlled retrotransposon transcription from a nonproductive TSS allows for rapid stress-induced activation, while preventing uncontrolled transposon activity in the genome.


Asunto(s)
Regulación de la Expresión Génica , Retroelementos , Sitio de Iniciación de la Transcripción , Secuencia de Bases , Catálisis , Cromatina/genética , Cromatina/metabolismo , Ensamble y Desensamble de Cromatina , Modelos Biológicos , Mutación , Nucleosomas , Fenotipo , Estrés Fisiológico , Secuencias Repetidas Terminales , Activación Transcripcional
2.
FEMS Yeast Res ; 17(1)2017 01 01.
Artículo en Inglés | MEDLINE | ID: mdl-28087675

RESUMEN

Life is maintained through alternating phases of cell division and quiescence. The causes and consequences of spontaneous mutations have been extensively explored in proliferating cells, and the major sources include errors of DNA replication and DNA repair. The foremost consequences are genetic variations within a cell population that can lead to heritable diseases and drive evolution. While most of our knowledge on DNA damage response and repair has been gained through cells actively dividing, it remains essential to also understand how DNA damage is metabolized in cells which are not dividing. In this review, we summarize the current knowledge concerning the type of lesions that arise in non-dividing budding and fission yeast cells, as well as the pathways used to repair them. We discuss the contribution of these models to our current understanding of age-related pathologies.


Asunto(s)
Reparación del ADN , Mutación , Saccharomyces cerevisiae/genética , Schizosaccharomyces/genética , Modelos Biológicos
3.
RNA Biol ; 14(7): 843-853, 2017 07 03.
Artículo en Inglés | MEDLINE | ID: mdl-28497998

RESUMEN

Most cells in nature are not actively dividing, yet are able to return to the cell cycle given the appropriate environmental signals. There is now ample evidence that quiescent G0 cells are not shut-down but still metabolically and transcriptionally active. Quiescent cells must maintain a basal transcriptional capacity to maintain transcripts and proteins necessary for survival. This implies a tight control over RNA polymerases: RNA pol II for mRNA transcription during G0, but especially RNA pol I and RNA pol III to maintain an appropriate level of structural RNAs, raising the possibility that specific transcriptional control mechanisms evolved in quiescent cells. In accordance with this, we recently discovered that RNA interference is necessary to control RNA polymerase I transcription during G0. While this mini-review focuses on yeast model organisms (Saccharomyces cerevisiae and Schizosaccharomyces pombe), parallels are drawn to other eukaryotes and mammalian systems, in particular stem cells.


Asunto(s)
Ciclo Celular/genética , Transcripción Genética , ARN Polimerasas Dirigidas por ADN/metabolismo , Epigénesis Genética , Código de Histonas , Modelos Biológicos
4.
Nature ; 469(7328): 112-5, 2011 Jan 06.
Artículo en Inglés | MEDLINE | ID: mdl-21151105

RESUMEN

Centromere-binding protein B (CENP-B) is a widely conserved DNA binding factor associated with heterochromatin and centromeric satellite repeats. In fission yeast, CENP-B homologues have been shown to silence long terminal repeat (LTR) retrotransposons by recruiting histone deacetylases. However, CENP-B factors also have unexplained roles in DNA replication. Here we show that a molecular function of CENP-B is to promote replication-fork progression through the LTR. Mutants have increased genomic instability caused by replication-fork blockage that depends on the DNA binding factor switch-activating protein 1 (Sap1), which is directly recruited by the LTR. The loss of Sap1-dependent barrier activity allows the unhindered progression of the replication fork, but results in rearrangements deleterious to the retrotransposon. We conclude that retrotransposons influence replication polarity through recruitment of Sap1 and transposition near replication-fork blocks, whereas CENP-B counteracts this activity and promotes fork stability. Our results may account for the role of LTR in fragile sites, and for the association of CENP-B with pericentromeric heterochromatin and tandem satellite repeats.


Asunto(s)
Proteína B del Centrómero/metabolismo , Replicación del ADN/genética , Genoma Fúngico/genética , Inestabilidad Genómica/genética , Retroelementos/genética , Schizosaccharomyces/genética , Secuencias Repetidas Terminales/genética , Proteína B del Centrómero/deficiencia , Proteína B del Centrómero/genética , Proteínas Cromosómicas no Histona/genética , Proteínas Cromosómicas no Histona/metabolismo , Secuencia Conservada/genética , Daño del ADN/genética , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Recombinación Genética , Schizosaccharomyces/metabolismo , Proteínas de Schizosaccharomyces pombe/genética , Proteínas de Schizosaccharomyces pombe/metabolismo
5.
Nature ; 479(7371): 135-8, 2011 Oct 16.
Artículo en Inglés | MEDLINE | ID: mdl-22002604

RESUMEN

Heterochromatin comprises tightly compacted repetitive regions of eukaryotic chromosomes. The inheritance of heterochromatin through mitosis requires RNA interference (RNAi), which guides histone modification during the DNA replication phase of the cell cycle. Here we show that the alternating arrangement of origins of replication and non-coding RNA in pericentromeric heterochromatin results in competition between transcription and replication in Schizosaccharomyces pombe. Co-transcriptional RNAi releases RNA polymerase II (Pol II), allowing completion of DNA replication by the leading strand DNA polymerase, and associated histone modifying enzymes that spread heterochromatin with the replication fork. In the absence of RNAi, stalled forks are repaired by homologous recombination without histone modification.


Asunto(s)
Replicación del ADN/fisiología , Silenciador del Gen , Heterocromatina/genética , Heterocromatina/metabolismo , Interferencia de ARN , ARN Polimerasa II/metabolismo , Schizosaccharomyces/genética , Centrómero/genética , Centrómero/metabolismo , Proteínas Cromosómicas no Histona/genética , Proteínas Cromosómicas no Histona/metabolismo , Daño del ADN , ADN Polimerasa Dirigida por ADN/metabolismo , Histonas/metabolismo , Recombinación Homóloga , Modelos Genéticos , Datos de Secuencia Molecular , ARN Interferente Pequeño/genética , ARN Interferente Pequeño/metabolismo , Origen de Réplica , Fase S , Proteínas de Schizosaccharomyces pombe/genética , Proteínas de Schizosaccharomyces pombe/metabolismo , Transcripción Genética
6.
EMBO J ; 28(6): 632-40, 2009 Mar 18.
Artículo en Inglés | MEDLINE | ID: mdl-19197239

RESUMEN

In humans, a mutation in the tyrosyl-DNA phosphodiesterase (Tdp1) is responsible for the recessively inherited syndrome spinocerebellar ataxia with axonal neuropathy (SCAN1). Tdp1 is a well-conserved DNA repair enzyme, which processes modified 3' phospho-DNA adducts in vitro. Here, we report that in the yeast Schizosaccharomyces pombe, tdp1 mutant cells progressively accumulate DNA damage and rapidly lose viability in a physiological G0/quiescent state. Remarkably, this effect is independent of topoisomerase I function. Moreover, we provide evidence that Tdp1, with the polynucleotide kinase (Pnk1), processes the same naturally occurring 3'-ends, produced from oxidative DNA damage in G0. We also found that one half of the dead cells lose their nuclear DNA. Nuclear DNA degradation is genetically programmed and mainly depends on the two DNA damage checkpoint responses, ATM/Tel1 and ATR/Rad3, reminiscent to programmed cell death. Diminishing the respiration rate or treating cells with a low concentration of antioxidants rescues the quiescent tdp1 mutant cells. These findings suggest that mitochondrial respiration causes neuronal cell death in the SCAN1 syndrome and in other neurological disorders.


Asunto(s)
División Celular , Daño del ADN , Hidrolasas Diéster Fosfóricas/metabolismo , Proteínas de Schizosaccharomyces pombe/metabolismo , Schizosaccharomyces/citología , Schizosaccharomyces/enzimología , Apoptosis , Núcleo Celular/enzimología , Roturas del ADN de Cadena Simple , Reparación del ADN , Viabilidad Microbiana , Mitocondrias/enzimología , Mutación/genética , Oxidación-Reducción , Fenotipo , Polinucleótido 5'-Hidroxil-Quinasa/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Fase de Descanso del Ciclo Celular
7.
Microbiol Mol Biol Rev ; 87(1): e0000821, 2023 03 21.
Artículo en Inglés | MEDLINE | ID: mdl-36629411

RESUMEN

Schizosaccharomyces pombe is an ascomycete fungus that divides by medial fission; it is thus commonly referred to as fission yeast, as opposed to the distantly related budding yeast Saccharomyces cerevisiae. The reproductive lifestyle of S. pombe relies on an efficient genetic sex determination system generating a 1:1 sex ratio and using alternating haploid/diploid phases in response to environmental conditions. In this review, we address how one haploid cell manages to generate two sister cells with opposite mating types, a prerequisite to conjugation and meiosis. This mating-type switching process depends on two highly efficient consecutive asymmetric cell divisions that rely on DNA replication, repair, and recombination as well as the structure and components of heterochromatin. We pay special attention to the intimate interplay between the genetic and epigenetic partners involved in this process to underscore the importance of basic research and its profound implication for a better understanding of chromatin biology.


Asunto(s)
Schizosaccharomyces , Schizosaccharomyces/genética , Schizosaccharomyces/metabolismo , Saccharomyces cerevisiae/genética , Reproducción/genética , Replicación del ADN
8.
EMBO J ; 27(9): 1378-87, 2008 May 07.
Artículo en Inglés | MEDLINE | ID: mdl-18388861

RESUMEN

Recombination is essential for the recovery of stalled/collapsed replication forks and therefore for the maintenance of genomic stability. The situation becomes critical when the replication fork collides with an unrepaired single-strand break and converts it into a one-ended double-strand break. We show in fission yeast that a unique broken replication fork requires the homologous recombination (HR) enzymes for cell viability. Two structure-specific heterodimeric endonucleases participate in two different resolution pathways. Mus81/Eme1 is essential when the sister chromatid is used for repair; conversely, Swi9/Swi10 is essential when an ectopic sequence is used for repair. Consequently, the utilization of these two HR modes of resolution mainly relies on the ratio of unique and repeated sequences present in various eukaryotic genomes. We also provide molecular evidence for sister recombination intermediates. These findings demonstrate that Mus81/Eme1 is the dedicated endonuclease that resolves sister chromatid recombination intermediates during the repair of broken replication forks.


Asunto(s)
Cromátides/genética , Replicación del ADN/fisiología , Proteínas de Unión al ADN/fisiología , Endonucleasas/fisiología , Recombinación Genética , Proteínas de Schizosaccharomyces pombe/fisiología , Inmunoprecipitación de Cromatina , ADN Helicasas/genética , ADN Helicasas/metabolismo , ADN Helicasas/fisiología , Replicación del ADN/genética , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Electroforesis en Gel Bidimensional , Endonucleasas/genética , Endonucleasas/metabolismo , Modelos Genéticos , Fenotipo , Recombinasa Rad51/genética , Recombinasa Rad51/metabolismo , Recombinasa Rad51/fisiología , Schizosaccharomyces/genética , Schizosaccharomyces/metabolismo , Schizosaccharomyces/fisiología , Proteínas de Schizosaccharomyces pombe/genética , Proteínas de Schizosaccharomyces pombe/metabolismo
10.
mBio ; 12(6): e0255821, 2021 12 21.
Artículo en Inglés | MEDLINE | ID: mdl-34724812

RESUMEN

Malaria parasites need to cope with changing environmental conditions that require strong countermeasures to ensure pathogen survival in the human and mosquito hosts. The molecular mechanisms that protect Plasmodium falciparum homeostasis during the complex life cycle remain unknown. Here, we identify cytosine methylation of tRNAAsp (GTC) as being critical to maintain stable protein synthesis. Using conditional knockout (KO) of a member of the DNA methyltransferase family, called Pf-DNMT2, RNA bisulfite sequencing demonstrated the selective cytosine methylation of this enzyme of tRNAAsp (GTC) at position C38. Although no growth defect on parasite proliferation was observed, Pf-DNMT2KO parasites showed a selective downregulation of proteins with a GAC codon bias. This resulted in a significant shift in parasite metabolism, priming KO parasites for being more sensitive to various types of stress. Importantly, nutritional stress made tRNAAsp (GTC) sensitive to cleavage by an unknown nuclease and increased gametocyte production (>6-fold). Our study uncovers an epitranscriptomic mechanism that safeguards protein translation and homeostasis of sexual commitment in malaria parasites. IMPORTANCE P. falciparum is the most virulent malaria parasite species, accounting for the majority of the disease mortality and morbidity. Understanding how this pathogen is able to adapt to different cellular and environmental stressors during its complex life cycle is crucial in order to develop new strategies to tackle the disease. In this study, we identified the writer of a specific tRNA cytosine methylation site as a new layer of epitranscriptomic regulation in malaria parasites that regulates the translation of a subset of parasite proteins (>400) involved in different metabolic pathways. Our findings give insight into a novel molecular mechanism that regulates P. falciparum response to drug treatment and sexual commitment.


Asunto(s)
Citosina/metabolismo , Metiltransferasas/metabolismo , Plasmodium falciparum/genética , Proteínas Protozoarias/metabolismo , ARN Protozoario/genética , ARN de Transferencia/genética , Metilación de ADN , Epigenoma , Humanos , Malaria Falciparum/parasitología , Metiltransferasas/genética , Plasmodium falciparum/enzimología , Plasmodium falciparum/fisiología , Proteínas Protozoarias/genética , Procesamiento Postranscripcional del ARN , ARN Protozoario/metabolismo , ARN de Transferencia/metabolismo , Estrés Fisiológico
11.
Nat Commun ; 11(1): 1973, 2020 04 24.
Artículo en Inglés | MEDLINE | ID: mdl-32332728

RESUMEN

The genetics of quiescence is an emerging field compared to that of growth, yet both states generate spontaneous mutations and genetic diversity fueling evolution. Reconciling mutation rates in dividing conditions and mutation accumulation as a function of time in non-dividing situations remains a challenge. Nitrogen-starved fission yeast cells reversibly arrest proliferation, are metabolically active and highly resistant to a variety of stresses. Here, we show that mutations in stress- and mitogen-activated protein kinase (S/MAPK) signaling pathways are enriched in aging cultures. Targeted resequencing and competition experiments indicate that these mutants arise in the first month of quiescence and expand clonally during the second month at the expense of the parental population. Reconstitution experiments show that S/MAPK modules mediate the sacrifice of many cells for the benefit of some mutants. These findings suggest that non-dividing conditions promote genetic diversity to generate a social cellular environment prone to kin selection.


Asunto(s)
Sistema de Señalización de MAP Quinasas , Mitosis , Mutación , Nitrógeno/fisiología , Schizosaccharomyces/genética , Schizosaccharomyces/fisiología , Técnicas de Cocultivo , ADN/metabolismo , Citometría de Flujo , Variación Genética , Genotipo , Fenotipo , Proteínas Serina-Treonina Quinasas/genética , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/fisiología , Proteínas de Schizosaccharomyces pombe/genética , Análisis de Secuencia de ADN , Transducción de Señal , Procesos Estocásticos
12.
DNA Repair (Amst) ; 7(1): 1-9, 2008 Jan 01.
Artículo en Inglés | MEDLINE | ID: mdl-17716957

RESUMEN

The Schizosaccharomyces pombe Swi5 protein forms two distinct protein complexes, Swi5-Sfr1 and Swi5-Swi2, each of which plays an important role in the related but functionally distinct processes of homologous recombination and mating-type switching, respectively. The Swi5-Sfr1 mediator complex has been shown to associate with the two RecA-like recombinases, Rhp51 (spRad51) and Dmc1, and to stimulate in vitro DNA strand exchange reactions mediated by these proteins. Genetic analysis indicates that Swi5-Sfr1 works independently of another mediator complex, Rhp55-Rhp57, during Rhp51-dependent recombinational repair. In addition, mutations affecting the two mediators generate distinct repair spectra of HO endonuclease-induced DNA double strand breaks, suggesting that these recombination mediators differently regulate recombination outcomes in an independent manner.


Asunto(s)
ADN de Hongos/genética , Recombinación Genética/fisiología , Proteínas de Schizosaccharomyces pombe/fisiología , Schizosaccharomyces/metabolismo , Reparación del ADN , Genes Fúngicos , Schizosaccharomyces/genética , Proteínas de Schizosaccharomyces pombe/genética
13.
Mol Biol Cell ; 17(1): 308-16, 2006 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-16251353

RESUMEN

DNA replication initiates at discrete origins along eukaryotic chromosomes. However, in most organisms, origin firing is not efficient; a specific origin will fire in some but not all cell cycles. This observation raises the question of how individual origins are selected to fire and whether origin firing is globally coordinated to ensure an even distribution of replication initiation across the genome. We have addressed these questions by determining the location of firing origins on individual fission yeast DNA molecules using DNA combing. We show that the firing of replication origins is stochastic, leading to a random distribution of replication initiation. Furthermore, origin firing is independent between cell cycles; there is no epigenetic mechanism causing an origin that fires in one cell cycle to preferentially fire in the next. Thus, the fission yeast strategy for the initiation of replication is different from models of eukaryotic replication that propose coordinated origin firing.


Asunto(s)
Replicación del ADN/genética , ADN de Hongos/biosíntesis , ADN de Hongos/genética , Origen de Réplica/genética , Schizosaccharomyces/genética , Genoma Fúngico/genética , Fase S , Schizosaccharomyces/citología , Proteínas de Schizosaccharomyces pombe/genética , Procesos Estocásticos
14.
Epigenetics Chromatin ; 12(1): 45, 2019 07 17.
Artículo en Inglés | MEDLINE | ID: mdl-31315658

RESUMEN

BACKGROUND: Cellular quiescence is a reversible differentiation state during which cells modify their gene expression program to inhibit metabolic functions and adapt to a new cellular environment. The epigenetic changes accompanying these alterations are not well understood. We used fission yeast cells as a model to study the regulation of quiescence. When these cells are starved for nitrogen, the cell cycle is arrested in G1, and the cells enter quiescence (G0). A gene regulatory program is initiated, including downregulation of thousands of genes-for example, those related to cell proliferation-and upregulation of specific genes-for example, autophagy genes-needed to adapt to the physiological challenge. These changes in gene expression are accompanied by a marked alteration of nuclear organization and chromatin structure. RESULTS: Here, we investigated the role of Leo1, a subunit of the conserved RNA polymerase-associated factor 1 (Paf1) complex, in the quiescence process using fission yeast as the model organism. Heterochromatic regions became very dynamic in fission yeast in G0 during nitrogen starvation. The reduction of heterochromatin in early G0 was correlated with reduced target of rapamycin complex 2 (TORC2) signaling. We demonstrated that cells lacking Leo1 show reduced survival in G0. In these cells, heterochromatic regions, including subtelomeres, were stabilized, and the expression of many genes, including membrane transport genes, was abrogated. TOR inhibition mimics the effect of nitrogen starvation, leading to the expression of subtelomeric genes, and this effect was suppressed by genetic deletion of leo1. CONCLUSIONS: We identified a protein, Leo1, necessary for survival during quiescence. Leo1 is part of a conserved protein complex, Paf1C, linked to RNA polymerase II. We showed that Leo1, acting downstream of TOR, is crucial for the dynamic reorganization of chromosomes and the regulation of gene expression during cellular quiescence. Genes encoding membrane transporters are not expressed in quiescent leo1 mutant cells, and cells die after 2 weeks of nitrogen starvation. Taken together, our results suggest that Leo1 is essential for the dynamic regulation of heterochromatin and gene expression during cellular quiescence.


Asunto(s)
Heterocromatina/metabolismo , Proteínas de Unión al ARN/metabolismo , Fase de Descanso del Ciclo Celular/genética , Ciclo Celular/genética , Epigénesis Genética , Regulación Fúngica de la Expresión Génica , Heterocromatina/genética , Histonas/metabolismo , Proteínas Nucleares/metabolismo , ARN Polimerasa II/genética , Proteínas de Unión al ARN/genética , Fase de Descanso del Ciclo Celular/fisiología , Schizosaccharomyces/genética , Schizosaccharomyces/metabolismo , Proteínas de Schizosaccharomyces pombe/genética , Proteínas de Schizosaccharomyces pombe/metabolismo
15.
Mol Cell Biol ; 25(1): 303-11, 2005 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-15601851

RESUMEN

A strand-specific imprint (break) controls mating-type switching in fission yeast. By introducing a thiamine repressible promoter upstream of the mat1 locus, we can force transcription through the imprinted region, erasing the imprint and inhibiting further mating-type switching, in a reversible manner. Starting from a synchronized, virgin M-cell population, we show that the site- and strand-specific break is formed when DNA replication intermediates appear at mat1 during the first S phase. The formation of the break is concomitant with a replication fork pause and binding of the Swi1 protein at mat1 until early G(2) and then rapidly disappears. Upon its formation, the break remains stable throughout the cell cycle and triggers mating-type switching during the second S phase. Finally, we have recreated the mating-type switching pedigree at the molecular and single-cell levels, allowing for the first time separation between the establishment of imprinting and its developmental fate.


Asunto(s)
Genes Fúngicos , Genes del Tipo Sexual de los Hongos , Schizosaccharomyces/genética , Schizosaccharomyces/fisiología , Alelos , Ciclo Celular , Proteínas de Ciclo Celular , Inmunoprecipitación de Cromatina , ADN/química , ADN/metabolismo , ADN de Hongos/metabolismo , Proteínas de Unión al ADN , Electroforesis en Gel Bidimensional , Fase G2 , Regulación Fúngica de la Expresión Génica , Impresión Genómica , Cinética , Modelos Genéticos , Linaje , Reacción en Cadena de la Polimerasa , Regiones Promotoras Genéticas , Unión Proteica , Fase S , Proteínas de Schizosaccharomyces pombe , Factores de Tiempo , Factores de Transcripción/metabolismo , Transcripción Genética
16.
Microb Cell ; 5(4): 169-183, 2018 Jan 16.
Artículo en Inglés | MEDLINE | ID: mdl-29610759

RESUMEN

Genetic and molecular studies have indicated that an epigenetic imprint at mat1, the sexual locus of fission yeast, initiates mating type switching. The polar DNA replication of mat1 generates an imprint on the Watson strand. The process by which the imprint is formed and maintained through the cell cycle remains unclear. To understand better the mechanism of imprint formation and stability, we characterized the recruitment of early players of mating type switching at the mat1 region. We found that the switch activating protein 1 (Sap1) is preferentially recruited inside the mat1M allele on a sequence (SS13) that enhances the imprint. The lysine specific demethylases, Lsd1/2, that control the replication fork pause at MPS1 and the formation of the imprint are specifically drafted inside of mat1, regardless of the allele. The CENP-B homolog, Abp1, is highly enriched next to mat1 but it is not required in the process. Additionally, we established the computational signature of the imprint. Using this signature, we show that both sides of the imprinted molecule are bound by Lsd1/2 and Sap1, suggesting a nucleoprotein protective structure defined as imprintosome.

17.
Curr Biol ; 14(21): 1924-8, 2004 Nov 09.
Artículo en Inglés | MEDLINE | ID: mdl-15530393

RESUMEN

The sexual locus mat1, in the fission yeast Schizosaccharomyces pombe, efficiently switches between the two mating types, P and M, by a process similar to gene conversion, using the silent mat2-P and mat3-M loci, respectively, as donors of the P and M genetic information . It has been proposed that an asymmetrically inherited, site- and strand-specific imprint at mat1 initiates the mating-type switching process . The molecular nature of the imprint is controversial; it was initially described as a double-strand break and then as a single-strand lesion or a strand-specific, alkali-labile modification . Here, we use E. coli DNA ligase in vitro to demonstrate that the imprint is a nick with no resection of nucleotides. By using ligation-mediated PCR, we show that the nick contains 3'OH and 5'OH unphosphorylated termini resistant to RNase treatments. This nonmutational mark on one of the DNA strands provides the first example of a novel type of imprint.


Asunto(s)
Cromosomas Fúngicos/genética , Daño del ADN , Genes Fúngicos/genética , Genes del Tipo Sexual de los Hongos , Genes de Cambio/genética , Schizosaccharomyces/genética , Animales , ADN Ligasas/metabolismo , Conversión Génica/genética , Oligonucleótidos , Reacción en Cadena de la Polimerasa
18.
Cell Cycle ; 16(18): 1643-1653, 2017 Sep 17.
Artículo en Inglés | MEDLINE | ID: mdl-28846478

RESUMEN

The nucleolus is a distinct compartment of the nucleus responsible for ribosome biogenesis. Mis-regulation of nucleolar functions and of the cellular translation machinery has been associated with disease, in particular with many types of cancer. Indeed, many tumor suppressors (p53, Rb, PTEN, PICT1, BRCA1) and proto-oncogenes (MYC, NPM) play a direct role in the nucleolus, and interact with the RNA polymerase I transcription machinery and the nucleolar stress response. We have identified Dicer and the RNA interference pathway as having an essential role in the nucleolus of quiescent Schizosaccharomyces pombe cells, distinct from pericentromeric silencing, by controlling RNA polymerase I release. We propose that this novel function is evolutionarily conserved and may contribute to the tumorigenic pre-disposition of DICER1 mutations in mammals.


Asunto(s)
Neoplasias/enzimología , Neoplasias/patología , Ribonucleasa III/metabolismo , Animales , Carcinogénesis/patología , Nucléolo Celular/metabolismo , ADN Ribosómico/genética , Genes Supresores de Tumor , Humanos , Neoplasias/genética
19.
Nat Commun ; 8(1): 1684, 2017 11 22.
Artículo en Inglés | MEDLINE | ID: mdl-29167439

RESUMEN

While the mechanisms of telomere maintenance has been investigated in dividing cells, little is known about the stability of telomeres in quiescent cells and how dysfunctional telomeres are processed in non-proliferating cells. Here we examine the stability of telomeres in quiescent cells using fission yeast. While wild type telomeres are stable in quiescence, we observe that eroded telomeres were highly rearranged during quiescence in telomerase minus cells. These rearrangements depend on homologous recombination (HR) and correspond to duplications of subtelomeric regions. HR is initiated at newly identified subtelomeric homologous repeated sequences (HRS). We further show that TERRA (Telomeric Repeat-containing RNA) is increased in post-mitotic cells with short telomeres and correlates with telomere rearrangements. Finally, we demonstrate that rearranged telomeres prevent cells to exit properly from quiescence. Taken together, we describe in fission yeast a mode of telomere repair mechanism specific to post-mitotic cells that is likely promoted by transcription.


Asunto(s)
Schizosaccharomyces/genética , Schizosaccharomyces/metabolismo , Homeostasis del Telómero/genética , Telómero/genética , Telómero/metabolismo , ADN de Hongos/genética , ADN de Hongos/metabolismo , Reordenamiento Génico , Inestabilidad Genómica , Recombinación Homóloga , Modelos Genéticos , ARN de Hongos/genética , ARN de Hongos/metabolismo , Reparación del ADN por Recombinación , Fase de Descanso del Ciclo Celular/genética , Schizosaccharomyces/citología , Proteínas de Schizosaccharomyces pombe/genética , Duplicaciones Segmentarias en el Genoma
20.
Elife ; 62017 12 18.
Artículo en Inglés | MEDLINE | ID: mdl-29252184

RESUMEN

To maintain life across a fluctuating environment, cells alternate between phases of cell division and quiescence. During cell division, the spontaneous mutation rate is expressed as the probability of mutations per generation (Luria and Delbrück, 1943; Lea and Coulson, 1949), whereas during quiescence it will be expressed per unit of time. In this study, we report that during quiescence, the unicellular haploid fission yeast accumulates mutations as a linear function of time. The novel mutational landscape of quiescence is characterized by insertion/deletion (indels) accumulating as fast as single nucleotide variants (SNVs), and elevated amounts of deletions. When we extended the study to 3 months of quiescence, we confirmed the replication-independent mutational spectrum at the whole-genome level of a clonally aged population and uncovered phenotypic variations that subject the cells to natural selection. Thus, our results support the idea that genomes continuously evolve under two alternating phases that will impact on their size and composition.


Asunto(s)
Mutación , Schizosaccharomyces/genética , Variación Biológica Poblacional , Schizosaccharomyces/fisiología , Selección Genética , Factores de Tiempo
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA