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Measuring DNA modifications with the comet assay: a compendium of protocols. Nat Protoc 2023; 18:929-989. [PMID: 36707722 DOI: 10.1038/s41596-022-00754-y] [Citation(s) in RCA: 94] [Impact Index Per Article: 94.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Accepted: 07/05/2022] [Indexed: 01/28/2023]
Abstract
The comet assay is a versatile method to detect nuclear DNA damage in individual eukaryotic cells, from yeast to human. The types of damage detected encompass DNA strand breaks and alkali-labile sites (e.g., apurinic/apyrimidinic sites), alkylated and oxidized nucleobases, DNA-DNA crosslinks, UV-induced cyclobutane pyrimidine dimers and some chemically induced DNA adducts. Depending on the specimen type, there are important modifications to the comet assay protocol to avoid the formation of additional DNA damage during the processing of samples and to ensure sufficient sensitivity to detect differences in damage levels between sample groups. Various applications of the comet assay have been validated by research groups in academia, industry and regulatory agencies, and its strengths are highlighted by the adoption of the comet assay as an in vivo test for genotoxicity in animal organs by the Organisation for Economic Co-operation and Development. The present document includes a series of consensus protocols that describe the application of the comet assay to a wide variety of cell types, species and types of DNA damage, thereby demonstrating its versatility.
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2
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Rácz HV, Mukhtar F, Imre A, Rádai Z, Gombert AK, Rátonyi T, Nagy J, Pócsi I, Pfliegler WP. How to characterize a strain? Clonal heterogeneity in industrial Saccharomyces influences both phenotypes and heterogeneity in phenotypes. Yeast 2021; 38:453-470. [PMID: 33844327 DOI: 10.1002/yea.3562] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Revised: 03/15/2021] [Accepted: 04/01/2021] [Indexed: 12/15/2022] Open
Abstract
Populations of microbes are constantly evolving heterogeneity that selection acts upon, yet heterogeneity is nontrivial to assess methodologically. The necessary practice of isolating single-cell colonies and thus subclone lineages for establishing, transferring, and using a strain results in single-cell bottlenecks with a generally neglected effect on the characteristics of the strain itself. Here, we present evidence that various subclone lineages for industrial yeasts sequenced for recent genomic studies show considerable differences, ranging from loss of heterozygosity to aneuploidies. Subsequently, we assessed whether phenotypic heterogeneity is also observable in industrial yeast, by individually testing subclone lineages obtained from products. Phenotyping of industrial yeast samples and their newly isolated subclones showed that single-cell bottlenecks during isolation can indeed considerably influence the observable phenotype. Next, we decoupled fitness distributions on the level of individual cells from clonal interference by plating single-cell colonies and quantifying colony area distributions. We describe and apply an approach using statistical modeling to compare the heterogeneity in phenotypes across samples and subclone lineages. One strain was further used to show how individual subclonal lineages are remarkably different not just in phenotype but also in the level of heterogeneity in phenotype. With these observations, we call attention to the fact that choosing an initial clonal lineage from an industrial yeast strain may vastly influence downstream performances and observations on karyotype, on phenotype, and also on heterogeneity.
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Affiliation(s)
- Hanna Viktória Rácz
- Department of Molecular Biotechnology and Microbiology, University of Debrecen, Debrecen, Hungary.,Doctoral School of Nutrition and Food Sciences, University of Debrecen, Debrecen, Hungary
| | - Fezan Mukhtar
- Department of Molecular Biotechnology and Microbiology, University of Debrecen, Debrecen, Hungary
| | - Alexandra Imre
- Department of Molecular Biotechnology and Microbiology, University of Debrecen, Debrecen, Hungary.,Kálmán Laki Doctoral School of Biomedical and Clinical Sciences, University of Debrecen, Debrecen, Hungary
| | - Zoltán Rádai
- MTA-ÖK Lendület Seed Ecology Research Group, Institute of Ecology and Botany, Centre for Ecological Research, Vácrátót, Hungary
| | | | - Tamás Rátonyi
- Institute of Land Use, Technology and Regional Development, University of Debrecen, Debrecen, Hungary
| | - János Nagy
- Institute of Land Use, Technology and Regional Development, University of Debrecen, Debrecen, Hungary
| | - István Pócsi
- Department of Molecular Biotechnology and Microbiology, University of Debrecen, Debrecen, Hungary
| | - Walter P Pfliegler
- Department of Molecular Biotechnology and Microbiology, University of Debrecen, Debrecen, Hungary
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3
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Dahiya R, Mohammad T, Alajmi MF, Rehman MT, Hasan GM, Hussain A, Hassan MI. Insights into the Conserved Regulatory Mechanisms of Human and Yeast Aging. Biomolecules 2020; 10:E882. [PMID: 32526825 PMCID: PMC7355435 DOI: 10.3390/biom10060882] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2020] [Revised: 05/22/2020] [Accepted: 05/27/2020] [Indexed: 12/12/2022] Open
Abstract
Aging represents a significant biological process having strong associations with cancer, diabetes, and neurodegenerative and cardiovascular disorders, which leads to progressive loss of cellular functions and viability. Astonishingly, age-related disorders share several genetic and molecular mechanisms with the normal aging process. Over the last three decades, budding yeast Saccharomyces cerevisiae has emerged as a powerful yet simple model organism for aging research. Genetic approaches using yeast RLS have led to the identification of hundreds of genes impacting lifespan in higher eukaryotes. Numerous interventions to extend yeast lifespan showed an analogous outcome in multi-cellular eukaryotes like fruit flies, nematodes, rodents, and humans. We collected and analyzed a multitude of observations from published literature and provide the contribution of yeast in the understanding of aging hallmarks most applicable to humans. Here, we discuss key pathways and molecular mechanisms that underpin the evolutionarily conserved aging process and summarize the current understanding and clinical applicability of its trajectories. Gathering critical information on aging biology would pave the way for future investigation targeted at the discovery of aging interventions.
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Affiliation(s)
- Rashmi Dahiya
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi 110025, India;
| | - Taj Mohammad
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi 110025, India;
| | - Mohamed F. Alajmi
- Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia; (M.F.A.); (M.T.R.); (A.H.)
| | - Md. Tabish Rehman
- Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia; (M.F.A.); (M.T.R.); (A.H.)
| | - Gulam Mustafa Hasan
- Department of Biochemistry, College of Medicine, Prince Sattam Bin Abdulaziz University, P.O. Box 173, Al-Kharj 11942, Saudi Arabia;
| | - Afzal Hussain
- Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia; (M.F.A.); (M.T.R.); (A.H.)
| | - Md. Imtaiyaz Hassan
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi 110025, India;
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Potocki L, Kuna E, Filip K, Kasprzyk B, Lewinska A, Wnuk M. Activation of transposable elements and genetic instability during long-term culture of the human fungal pathogen Candida albicans. Biogerontology 2019; 20:457-474. [PMID: 30989423 PMCID: PMC6593122 DOI: 10.1007/s10522-019-09809-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Accepted: 04/08/2019] [Indexed: 02/08/2023]
Abstract
It has been repeatedly reported that transposable elements (TE) become active and/or mobile in the genomes of replicatively and stress-induced senescent mammalian cells. However, the biological role of senescence-associated transposon activation and its occurrence and relevance in other eukaryotic cells remain to be elucidated. In the present study, Candida albicans, a prevalent opportunistic fungal pathogen in humans, was used to analyze changes in gene copy number of selected TE, namely Cirt2, Moa and Cmut1 during long-term culture (up to 90 days). The effects of stress stimuli (fluconazole, hydrogen peroxide, hypochlorite) and ploidy state (haploid, diploid, tetraploid cells) were also considered. An increase in copy number of Cirt2 and Moa was the most accented in tetraploid cells after 90 days of culture that was accompanied by changes in karyotype patterns and slightly more limited growth rate compared to haploid and diploid cells. Stress stimuli did not potentiate TE activity. Elevation in chromosomal DNA breaks was also observed during long-term culture of cells of different ploidy, however this was not correlated with increased TE activity. Our results suggest that increased TE activity may promote genomic diversity and plasticity, and cellular heterogeneity during long-term culture of C. albicans cells.
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Affiliation(s)
- Leszek Potocki
- Department of Genetics, Faculty of Biotechnology, University of Rzeszow, Pigonia 1, 35-310, Rzeszow, Poland
| | - Ewelina Kuna
- Department of Genetics, Faculty of Biotechnology, University of Rzeszow, Pigonia 1, 35-310, Rzeszow, Poland
| | - Kamila Filip
- Department of Genetics, Faculty of Biotechnology, University of Rzeszow, Pigonia 1, 35-310, Rzeszow, Poland
| | - Beata Kasprzyk
- Department of Genetics, Faculty of Biotechnology, University of Rzeszow, Pigonia 1, 35-310, Rzeszow, Poland
| | - Anna Lewinska
- Department of Cell Biochemistry, Faculty of Biotechnology, University of Rzeszow, Pigonia 1, 35-310, Rzeszow, Poland.
| | - Maciej Wnuk
- Department of Genetics, Faculty of Biotechnology, University of Rzeszow, Pigonia 1, 35-310, Rzeszow, Poland.
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5
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Krol K, Antoniuk-Majchrzak J, Skoneczny M, Sienko M, Jendrysek J, Rumienczyk I, Halas A, Kurlandzka A, Skoneczna A. Lack of G1/S control destabilizes the yeast genome via replication stress-induced DSBs and illegitimate recombination. J Cell Sci 2018; 131:jcs.226480. [PMID: 30463853 DOI: 10.1242/jcs.226480] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Accepted: 11/05/2018] [Indexed: 12/13/2022] Open
Abstract
The protein Swi6 in Saccharomyces cerevisiae is a cofactor in two complexes that regulate the transcription of the genes controlling the G1/S transition. It also ensures proper oxidative and cell wall stress responses. Previously, we found that Swi6 was crucial for the survival of genotoxic stress. Here, we show that a lack of Swi6 causes replication stress leading to double-strand break (DSB) formation, inefficient DNA repair and DNA content alterations, resulting in high cell mortality. Comparative genome hybridization experiments revealed that there was a random genome rearrangement in swi6Δ cells, whereas in diploid swi6Δ/swi6Δ cells, chromosome V is duplicated. SWI4 and PAB1, which are located on chromosome V and are known multicopy suppressors of swi6Δ phenotypes, partially reverse swi6Δ genome instability when overexpressed. Another gene on chromosome V, RAD51, also supports swi6Δ survival, but at a high cost; Rad51-dependent illegitimate recombination in swi6Δ cells appears to connect DSBs, leading to genome rearrangement and preventing cell death.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Kamil Krol
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
| | | | - Marek Skoneczny
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
| | - Marzena Sienko
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
| | - Justyna Jendrysek
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
| | - Izabela Rumienczyk
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
| | - Agnieszka Halas
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
| | - Anna Kurlandzka
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
| | - Adrianna Skoneczna
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
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6
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Szwajczak E, Fijalkowska IJ, Suski C. The importance of an interaction network for proper DNA polymerase ζ heterotetramer activity. Curr Genet 2018; 64:575-580. [PMID: 29189894 PMCID: PMC5948306 DOI: 10.1007/s00294-017-0789-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Revised: 11/23/2017] [Accepted: 11/27/2017] [Indexed: 12/22/2022]
Abstract
Precisely controlled mechanisms have been evolved to rescue impeded DNA replication resulting from encountered obstacles and involve a set of low-fidelity translesion synthesis (TLS) DNA polymerases. Studies in recent years have brought new insights into those TLS polymerases, especially concerning the structure and subunit composition of DNA polymerase zeta (Pol ζ). Pol ζ is predominantly involved in induced mutagenesis as well as the bypass of noncanonical DNA structures, and it is proficient in extending from terminal mismatched nucleotides incorporated by major replicative DNA polymerases. Two active forms of Pol ζ, heterodimeric (Pol ζ2) and heterotetrameric (Pol ζ4) ones, have been identified and studied. Here, in the light of recent publications regarding induced and spontaneous mutagenesis and diverse interactions within Pol ζ holoenzyme, combined with Pol ζ binding to the TLS polymerase Rev1p, we discuss the subunit composition of Pol ζ in various cellular physiological conditions. Available data show that it is the heterotetrameric form of Pol ζ that is involved both during spontaneous and induced mutagenesis, and underline the importance of interactions within Pol ζ when an increased Pol ζ recruitment occurs. Understanding Pol ζ function in the bypass of DNA obstacles would give a significant insight into cellular tolerance of DNA damage, genetic instability and the onset of cancer progression.
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Affiliation(s)
- Ewa Szwajczak
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106, Warszawa, Poland
| | - Iwona J Fijalkowska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106, Warszawa, Poland
| | - Catherine Suski
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106, Warszawa, Poland.
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7
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Tight Regulation of Srs2 Helicase Activity Is Crucial for Proper Functioning of DNA Repair Mechanisms. G3-GENES GENOMES GENETICS 2018. [PMID: 29531123 PMCID: PMC5940153 DOI: 10.1534/g3.118.200181] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Proper DNA damage repair is one of the most vital and fundamental functions of every cell. Several different repair mechanisms exist to deal with various types of DNA damage, in various stages of the cell cycle and under different conditions. Homologous recombination is one of the most important repair mechanisms in all organisms. Srs2, a regulator of homologous recombination, is a DNA helicase involved in DNA repair, cell cycle progression and genome integrity. Srs2 can remove Rad51 from ssDNA, and is thought to inhibit unscheduled recombination. However, Srs2 has to be precisely regulated, as failure to do so is toxic and can lead to cell death. We noticed that a very slight elevation of the levels of Srs2 (by addition of a single extra copy of the SRS2 gene) leads to hyper-sensitivity of yeast cells to methyl methanesulfonate (MMS, a DNA damaging agent). This effect is seen in haploid, but not in diploid, cells. We analyzed the mechanism that controls haploid/diploid sensitivity and arrived to the conclusion that the sensitivity requires the activity of RAD59 and RDH54, whose expression in diploid cells is repressed. We carried out a mutational analysis of Srs2 to determine the regions of the protein required for the sensitization to genotoxins. Interestingly, Srs2 needs the HR machinery and its helicase activity for its toxicity, but does not need to dismantle Rad51. Our work underscores the tight regulation that is required on the levels of Srs2 activity, and the fact that Srs2 helicase activity plays a more central role in DNA repair than the ability of Srs2 to dismantle Rad51 filaments.
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8
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Krol K, Jendrysek J, Debski J, Skoneczny M, Kurlandzka A, Kaminska J, Dadlez M, Skoneczna A. Ribosomal DNA status inferred from DNA cloud assays and mass spectrometry identification of agarose-squeezed proteins interacting with chromatin (ASPIC-MS). Oncotarget 2018; 8:24988-25004. [PMID: 28212567 PMCID: PMC5421904 DOI: 10.18632/oncotarget.15332] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 01/23/2017] [Indexed: 11/25/2022] Open
Abstract
Ribosomal RNA-encoding genes (rDNA) are the most abundant genes in eukaryotic genomes. To meet the high demand for rRNA, rDNA genes are present in multiple tandem repeats clustered on a single or several chromosomes and are vastly transcribed. To facilitate intensive transcription and prevent rDNA destabilization, the rDNA-encoding portion of the chromosome is confined in the nucleolus. However, the rDNA region is susceptible to recombination and DNA damage, accumulating mutations, rearrangements and atypical DNA structures. Various sophisticated techniques have been applied to detect these abnormalities. Here, we present a simple method for the evaluation of the activity and integrity of an rDNA region called a “DNA cloud assay”. We verified the efficacy of this method using yeast mutants lacking genes important for nucleolus function and maintenance (RAD52, SGS1, RRM3, PIF1, FOB1 and RPA12). The DNA cloud assay permits the evaluation of nucleolus status and is compatible with downstream analyses, such as the chromosome comet assay to identify DNA structures present in the cloud and mass spectrometry of agarose squeezed proteins (ASPIC-MS) to detect nucleolar DNA-bound proteins, including Las17, the homolog of human Wiskott-Aldrich Syndrome Protein (WASP).
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Affiliation(s)
- Kamil Krol
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Laboratory of Mutagenesis and DNA Repair, Warsaw, 02-106, Poland
| | - Justyna Jendrysek
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Laboratory of Mutagenesis and DNA Repair, Warsaw, 02-106, Poland
| | - Janusz Debski
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Mass Spectrometry Laboratory, Warsaw, 02-106, Poland
| | - Marek Skoneczny
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Department of Genetics, Warsaw, 02-106, Poland
| | - Anna Kurlandzka
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Department of Genetics, Warsaw, 02-106, Poland
| | - Joanna Kaminska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Department of Genetics, Warsaw, 02-106, Poland
| | - Michal Dadlez
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Mass Spectrometry Laboratory, Warsaw, 02-106, Poland
| | - Adrianna Skoneczna
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Laboratory of Mutagenesis and DNA Repair, Warsaw, 02-106, Poland
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9
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Abstract
Ploidy is considered a very stable cellular characteristic. Although rare, changes in ploidy play important roles in the acquisition of long-term adaptations. Since these duplications allow the subsequent loss of individual chromosomes and accumulation of mutations, changes in ploidy can also cause genomic instability, and have been found to promote cancer. Despite the importance of the subject, measuring the rate of whole-genome duplications has proven extremely challenging. We have recently measured the rate of diploidization in yeast using long-term, in-lab experiments. We found that spontaneous diploidization occurs frequently, by two different mechanisms: endoreduplication and mating type switching. Despite its common occurrence, spontaneous diploidization is usually selected against, although it can be advantageous under some stressful conditions. Our results have implications for the understanding of evolutionary processes, as well as for the use of yeast cells in biotechnological applications.
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10
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Spontaneous Changes in Ploidy Are Common in Yeast. Curr Biol 2018; 28:825-835.e4. [PMID: 29502947 DOI: 10.1016/j.cub.2018.01.062] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Revised: 12/11/2017] [Accepted: 01/22/2018] [Indexed: 12/19/2022]
Abstract
Changes in ploidy are relatively rare, but play important roles in the development of cancer and the acquisition of long-term adaptations. Genome duplications occur across the tree of life, and can alter the rate of adaptive evolution. Moreover, by allowing the subsequent loss of individual chromosomes and the accumulation of mutations, changes in ploidy can promote genomic instability and/or adaptation. Although many studies have been published in the last years about changes in chromosome number and their evolutionary consequences, tracking and measuring the rate of whole-genome duplications have been extremely challenging. We have systematically studied the appearance of diploid cells among haploid yeast cultures evolving for over 100 generations in different media. We find that spontaneous diploidization is a relatively common event, which is usually selected against, but under certain stressful conditions may become advantageous. Furthermore, we were able to detect and distinguish between two different mechanisms of diploidization, one that requires whole-genome duplication (endoreduplication) and a second that involves mating-type switching despite the use of heterothallic strains. Our results have important implications for our understanding of evolution and adaptation in fungal pathogens and the development of cancer, and for the use of yeast cells in biotechnological applications.
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11
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Rad5 coordinates translesion DNA synthesis pathway by recognizing specific DNA structures in saccharomyces cerevisiae. Curr Genet 2018; 64:889-899. [PMID: 29396601 DOI: 10.1007/s00294-018-0807-y] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Revised: 01/11/2018] [Accepted: 01/25/2018] [Indexed: 02/07/2023]
Abstract
DNA repair is essential to maintain genome integrity. In addition to various DNA repair pathways dealing with specific types of DNA lesions, DNA damage tolerance (DDT) promotes the bypass of DNA replication blocks encountered by the replication fork to prevent cell death. Budding yeast Rad5 plays an essential role in the DDT pathway and its structure indicates that Rad5 recognizes damaged DNA or stalled replication forks, suggesting that Rad5 plays an important role in the DDT pathway choice. It has been reported that Rad5 forms subnuclear foci in the presence of methyl methanesulfonate (MMS) during the S phase. By analyzing the formation of Rad5 foci after MMS treatment, we showed that some specific DNA structures rather than mono-ubiquitination of proliferating cell nuclear antigen are required for the recruitment of Rad5 to the damaged site. Moreover, inactivation of the base excision repair (BER) pathway greatly decreased the Rad5 focus formation, suggesting that Rad5 recognizes specific DNA structures generated by BER. We also identified a negative role of overexpressed translesion synthesis polymerase Polη in the formation of Rad5 foci. Based on these data, we propose a modified DDT pathway model in which Rad5 plays a role in activating the DDT pathway.
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12
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Leshets M, Ramamurthy D, Lisby M, Lehming N, Pines O. Fumarase is involved in DNA double-strand break resection through a functional interaction with Sae2. Curr Genet 2017; 64:697-712. [DOI: 10.1007/s00294-017-0786-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Revised: 11/19/2017] [Accepted: 11/22/2017] [Indexed: 11/28/2022]
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13
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Maicher A, Kupiec M. Rnr1's role in telomere elongation cannot be replaced by Rnr3: a role beyond dNTPs? Curr Genet 2017; 64:547-550. [PMID: 29119271 DOI: 10.1007/s00294-017-0779-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Accepted: 11/03/2017] [Indexed: 11/29/2022]
Abstract
Telomeres, the nucleoprotein complexes at the end of eukaryotic chromosomes, protect them from degradation and ensure the replicative capacity of cells. In most human tumors and in budding yeast, telomere length is maintained by the activity of telomerase, an enzyme that adds dNTPs according to an internal RNA template. The dNTPs are generated with the help of the ribonucleotide reductase (RNR) complex. We have recently generated strains lacking the large subunit of RNR, Rnr1, which were kept viable by the expression of RNR complexes containing the Rnr1 homolog, Rnr3. Interestingly, we found that these Rnr1-deficient strains have short telomeres that are stably maintained, but cannot become efficiently elongated by telomerase. Thus, a basic maintenance of short telomeres is possible under conditions, where Rnr1 activity is absent, but a sustained elongation of short telomeres fully depends on Rnr1 activity. We show that Rnr3 cannot compensate for this telomeric function of Rnr1 even when overall cellular dNTP values are restored. This suggests that Rnr1 plays a role in telomere elongation beyond increasing cellular dNTP levels. Furthermore, our data indicate that telomerase may act in two different modes, one that is capable of coping with the "end-replication problem" and is functional even in the absence of Rnr1 and another required for the sustained elongation of short telomeres, which fully depends on the presence of Rnr1. Supply of dNTPs for telomere elongation is provided by the Mec1ATR checkpoint, both during regular DNA replication and upon replication fork stalling. We discuss the implications of these results on telomere maintenance in yeast and cancer cells.
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Affiliation(s)
- André Maicher
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Ramat Aviv, Tel Aviv, 6997801, Israel
| | - Martin Kupiec
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Ramat Aviv, Tel Aviv, 6997801, Israel.
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14
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Nikolaou C. Invisible cities: segregated domains in the yeast genome with distinct structural and functional attributes. Curr Genet 2017; 64:247-258. [PMID: 28780612 DOI: 10.1007/s00294-017-0731-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Revised: 07/31/2017] [Accepted: 08/02/2017] [Indexed: 02/07/2023]
Abstract
Recent advances in our understanding of the three-dimensional organization of the eukaryotic nucleus have rendered the spatial distribution of genes increasingly relevant. In a recent work (Tsochatzidou et al., Nucleic Acids Res 45:5818-5828, 2017), we proposed the existence of a functional compartmentalization of the yeast genome according to which, genes occupying the chromosomal regions at the nuclear periphery have distinct structural, functional and evolutionary characteristics compared to their centromeric-proximal counterparts. Around the same time, it was also shown that the genome of Saccharomyces cerevisiae is organized in topologically associated domains (TADs), which are largely associated with the replication timing. In this work, we proceed to investigate whether such units of three-dimensional genomic organization can be linked to transcriptional activity as a driving force for the shaping of genomic architecture. Through the application of a simple boundary-calling criterion in genome-wide 3C data, we define ~100 TAD-like domains which can be clustered in six different classes with radically different nucleosomal organizations, significant variations in transcription factor binding and uneven chromosomal distribution. Approximately ~20% of the genome is found to be confined in regions with "closed" chromatin structure around gene promoters. Most interestingly, we find both "open" and "closed" regions to be segregated, in the sense that they tend to avoid inter-chromosomal interactions. Our data further enforce the notion of a marked compartmentalization of the yeast genome in isolated territories, with implications in its function and evolution.
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Affiliation(s)
- Christoforos Nikolaou
- Computational Genomics Group, Department of Biology, University of Crete, 70013, Herakleion, Greece.
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15
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Harari Y, Kupiec M. Mec1 ATR is needed for extensive telomere elongation in response to ethanol in yeast. Curr Genet 2017; 64:223-234. [PMID: 28780613 DOI: 10.1007/s00294-017-0728-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Revised: 07/26/2017] [Accepted: 07/31/2017] [Indexed: 11/26/2022]
Abstract
Telomere length homeostasis is essential for cell survival. In humans, telomeres shorten as a function of age. Short telomeres are known determinants of cell senescence and longevity. The yeast Saccharomyces cerevisiae expresses telomerase and maintains a strict telomere length homeostasis during vegetative growth. We have previously reported that different environmental signals promote changes in telomere length in S. cerevisiae. In particular, exposure to ethanol induces an extensive telomere elongation response due to a reduction in RAP1 mRNA and protein levels. Here we show that the reduction in Rap1 protein levels disrupts the physical interaction between Rap1 and Rif1, which in turn reduces the recruitment of these two proteins to telomeres during G2-phase. Although elongation of the shortest telomeres has been shown to depend on the Rif2 telomeric protein and on the Tel1(ATM) protein kinase, we show here that the extensive telomere elongation in response to ethanol exposure is Rif1 and Mec1 (ATR)-dependent. Our results fit a model in which Rif1 and Rap1 form a complex that is loaded onto telomeres at the end of S-phase. Reduced levels of the Rap1-Rif1 complex in ethanol lead to continuous telomere elongation in a Mec1-dependent process.
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Affiliation(s)
- Yaniv Harari
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Ramat Aviv, Tel Aviv, Israel
| | - Martin Kupiec
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Ramat Aviv, Tel Aviv, Israel.
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