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Shaban K, Dolson A, Fisher A, Lessard E, Sauty SM, Yankulov K. TOF1 and RRM3 reveal a link between gene silencing and the pausing of replication forks. Curr Genet 2023; 69:235-249. [PMID: 37347284 DOI: 10.1007/s00294-023-01273-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Revised: 06/01/2023] [Accepted: 06/14/2023] [Indexed: 06/23/2023]
Abstract
Eukaryotic DNA replication is accompanied by the disassembly and reassembly of nucleosomes and the transmission of epigenetic marks to the newly assembled chromatids. Several histone chaperones, including CAF-1 and Asf1p, are central to these processes. On the other hand, replication forks pause at numerous positions throughout the genome, but it is not known if and how this pausing affects the reassembly and maintenance of chromatin structures. Here, we applied drug-free gene silencing assays to analyze the genetic interactions between CAC1, ASF1, and two genes that regulate the stability of the paused replisome (TOF1) and the resumption of elongation (RRM3). Our results show that TOF1 and RRM3 differentially interact with CAF-1 and ASF1 and that the deletions of TOF1 and RRM3 lead to reduced silencing and increased frequency of epigenetic conversions at three loci in the genome of S. cerevisiae. Our study adds details to the known activities of CAF-1 and Asf1p and suggests that the pausing of the replication fork can lead to epigenetic instability.
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Affiliation(s)
- Kholoud Shaban
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, N1G2W1, Canada
| | - Andrew Dolson
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, N1G2W1, Canada
| | - Ashley Fisher
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, N1G2W1, Canada
| | - Emma Lessard
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, N1G2W1, Canada
| | - Safia Mahabub Sauty
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, N1G2W1, Canada
| | - Krassimir Yankulov
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, N1G2W1, Canada.
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Sauty SM, Yankulov K. Analyses of POL30 (PCNA) reveal positional effects in transient repression or bi-modal active/silent state at the sub-telomeres of S. cerevisiae. Epigenetics Chromatin 2023; 16:40. [PMID: 37858268 PMCID: PMC10585736 DOI: 10.1186/s13072-023-00513-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Accepted: 10/06/2023] [Indexed: 10/21/2023] Open
Abstract
BACKGROUND Classical studies on position effect variegation in Drosophila have demonstrated the existence of bi-modal Active/Silent state of the genes juxtaposed to heterochromatin. Later studies with irreversible methods for the detection of gene repression have revealed a similar phenomenon at the telomeres of Saccharomyces cerevisiae and other species. In this study, we used dual reporter constructs and a combination of reversible and non-reversible methods to present evidence for the different roles of PCNA and histone chaperones in the stability and the propagation of repressed states at the sub-telomeres of S. cerevisiae. RESULTS We show position dependent transient repression or bi-modal expression of reporter genes at the VIIL sub-telomere. We also show that mutations in the replicative clamp POL30 (PCNA) or the deletion of the histone chaperone CAF1 or the RRM3 helicase lead to transient de-repression, while the deletion of the histone chaperone ASF1 causes a shift from transient de-repression to a bi-modal state of repression. We analyze the physical interaction of CAF1 and RRM3 with PCNA and discuss the implications of these findings for our understanding of the stability and transmission of the epigenetic state of the genes. CONCLUSIONS There are distinct modes of gene silencing, bi-modal and transient, at the sub-telomeres of S. cerevisiae. We characterise the roles of CAF1, RRM3 and ASF1 in these modes of gene repression. We suggest that the interpretations of past and future studies should consider the existence of the dissimilar states of gene silencing.
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Affiliation(s)
- Safia Mahabub Sauty
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, N1G2W1, Canada
| | - Krassimir Yankulov
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, N1G2W1, Canada.
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Shaban K, Sauty SM, Fisher A, Cheng A, Yankulov K. Evaluation of drug-free methods for the detection of gene silencing in Saccharomyces cerevisiae. Biochem Cell Biol 2023; 101:125-130. [PMID: 36661263 DOI: 10.1139/bcb-2022-0243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Multiple studies in Saccharomyces cerevisiae have measured the levels of gene silencing by inserting the URA3 gene at various loci and selecting against URA3-expressing cells by 5-flouroorotic acid (5-FOA). However, 5-FOA affects the cellular pools of dNTPs and can produce side effects. To circumvent this issue, we and others have introduced drug-free techniques to detect silent and active gene states. In this study, we compared three drug-free methods based on the expression of fluorescent reporters in the VIIL telomere of S. cerevisiae. Our results point out that only one of these methods is suitable for large-scale drug-free analyses of gene silencing.
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Affiliation(s)
- Kholoud Shaban
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Safia Mahabub Sauty
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Ashley Fisher
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Ashley Cheng
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Krassimir Yankulov
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada
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Urban JA, Ranjan R, Chen X. Asymmetric Histone Inheritance: Establishment, Recognition, and Execution. Annu Rev Genet 2022; 56:113-143. [PMID: 35905975 PMCID: PMC10054593 DOI: 10.1146/annurev-genet-072920-125226] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The discovery of biased histone inheritance in asymmetrically dividing Drosophila melanogaster male germline stem cells demonstrates one means to produce two distinct daughter cells with identical genetic material. This inspired further studies in different systems, which revealed that this phenomenon may be a widespread mechanism to introduce cellular diversity. While the extent of asymmetric histone inheritance could vary among systems, this phenomenon is proposed to occur in three steps: first, establishment of histone asymmetry between sister chromatids during DNA replication; second, recognition of sister chromatids carrying asymmetric histone information during mitosis; and third, execution of this asymmetry in the resulting daughter cells. By compiling the current knowledge from diverse eukaryotic systems, this review comprehensively details and compares known chromatin factors, mitotic machinery components, and cell cycle regulators that may contribute to each of these three steps. Also discussed are potential mechanisms that introduce and regulate variable histone inheritance modes and how these different modes may contribute to cell fate decisions in multicellular organisms.
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Affiliation(s)
- Jennifer A Urban
- Department of Biology, The Johns Hopkins University, Baltimore, Maryland, USA;
| | - Rajesh Ranjan
- Department of Biology, The Johns Hopkins University, Baltimore, Maryland, USA; .,Howard Hughes Medical Institute, The Johns Hopkins University, Baltimore, Maryland, USA; ,
| | - Xin Chen
- Department of Biology, The Johns Hopkins University, Baltimore, Maryland, USA; .,Howard Hughes Medical Institute, The Johns Hopkins University, Baltimore, Maryland, USA; ,
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Dolson A, Sauty SM, Shaban K, Yankulov K. Dbf4-Dependent Kinase: DDK-ated to post-initiation events in DNA replication. Cell Cycle 2021; 20:2348-2360. [PMID: 34662256 DOI: 10.1080/15384101.2021.1986999] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Dbf4-Dependent Kinase (DDK) has a well-established essential role at origins of DNA replication, where it phosphorylates and activates the replicative MCM helicase. It also acts in the response to mutagens and in DNA repair as well as in key steps during meiosis. Recent studies have indicated that, in addition to the MCM helicase, DDK phosphorylates several substrates during the elongation stage of DNA replication or upon replication stress. However, these activities of DDK are not essential for viability. Dbf4-Dependent Kinase is also emerging as a key factor in the regulation of genome-wide origin firing and in replication-coupled chromatin assembly. In this review, we summarize recent progress in our understanding of the diverse roles of DDK.
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Affiliation(s)
- Andrew Dolson
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Safia Mahabub Sauty
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Kholoud Shaban
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Krassimir Yankulov
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
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6
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Aricthota S, Haldar D. DDK/Hsk1 phosphorylates and targets fission yeast histone deacetylase Hst4 for degradation to stabilize stalled DNA replication forks. eLife 2021; 10:70787. [PMID: 34608864 PMCID: PMC8565929 DOI: 10.7554/elife.70787] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 10/01/2021] [Indexed: 01/01/2023] Open
Abstract
In eukaryotes, paused replication forks are prone to collapse, which leads to genomic instability, a hallmark of cancer. Dbf4-dependent kinase (DDK)/Hsk1Cdc7 is a conserved replication initiator kinase with conflicting roles in replication stress response. Here, we show that fission yeast DDK/Hsk1 phosphorylates sirtuin, Hst4 upon replication stress at C-terminal serine residues. Phosphorylation of Hst4 by DDK marks it for degradation via the ubiquitin ligase SCFpof3. Phosphorylation-defective hst4 mutant (4SA-hst4) displays defective recovery from replication stress, faulty fork restart, slow S-phase progression and decreased viability. The highly conserved fork protection complex (FPC) stabilizes stalled replication forks. We found that the recruitment of FPC components, Swi1 and Mcl1 to the chromatin is compromised in the 4SA-hst4 mutant, although whole cell levels increased. These defects are dependent upon H3K56ac and independent of intra S-phase checkpoint activation. Finally, we show conservation of H3K56ac-dependent regulation of Timeless, Tipin, and And-1 in human cells. We propose that degradation of Hst4 via DDK increases H3K56ac, changing the chromatin state in the vicinity of stalled forks facilitating recruitment and function of FPC. Overall, this study identified a crucial role of DDK and FPC in the regulation of replication stress response with implications in cancer therapeutics.
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Affiliation(s)
- Shalini Aricthota
- Laboratory of Chromatin Biology and Epigenetics, Centre for DNA Fingerprinting and Diagnostics, Hyderabad, India.,Graduate Studies, Manipal Academy of Higher Education, Manipal, India
| | - Devyani Haldar
- Laboratory of Chromatin Biology and Epigenetics, Centre for DNA Fingerprinting and Diagnostics, Hyderabad, India
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Shyian M, Shore D. Approaching Protein Barriers: Emerging Mechanisms of Replication Pausing in Eukaryotes. Front Cell Dev Biol 2021; 9:672510. [PMID: 34124054 PMCID: PMC8194067 DOI: 10.3389/fcell.2021.672510] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Accepted: 05/03/2021] [Indexed: 11/13/2022] Open
Abstract
During nuclear DNA replication multiprotein replisome machines have to jointly traverse and duplicate the total length of each chromosome during each cell cycle. At certain genomic locations replisomes encounter tight DNA-protein complexes and slow down. This fork pausing is an active process involving recognition of a protein barrier by the approaching replisome via an evolutionarily conserved Fork Pausing/Protection Complex (FPC). Action of the FPC protects forks from collapse at both programmed and accidental protein barriers, thus promoting genome integrity. In addition, FPC stimulates the DNA replication checkpoint and regulates topological transitions near the replication fork. Eukaryotic cells have been proposed to employ physiological programmed fork pausing for various purposes, such as maintaining copy number at repetitive loci, precluding replication-transcription encounters, regulating kinetochore assembly, or controlling gene conversion events during mating-type switching. Here we review the growing number of approaches used to study replication pausing in vivo and in vitro as well as the characterization of additional factors recently reported to modulate fork pausing in different systems. Specifically, we focus on the positive role of topoisomerases in fork pausing. We describe a model where replisome progression is inherently cautious, which ensures general preservation of fork stability and genome integrity but can also carry out specialized functions at certain loci. Furthermore, we highlight classical and novel outstanding questions in the field and propose venues for addressing them. Given how little is known about replisome pausing at protein barriers in human cells more studies are required to address how conserved these mechanisms are.
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Affiliation(s)
- Maksym Shyian
- Department of Molecular Biology, Institute of Genetics and Genomics of Geneva (iGE3), University of Geneva, Geneva, Switzerland
| | - David Shore
- Department of Molecular Biology, Institute of Genetics and Genomics of Geneva (iGE3), University of Geneva, Geneva, Switzerland
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Shaban K, Sauty SM, Yankulov K. Variation, Variegation and Heritable Gene Repression in S. cerevisiae. Front Genet 2021; 12:630506. [PMID: 33747046 PMCID: PMC7970126 DOI: 10.3389/fgene.2021.630506] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Accepted: 02/08/2021] [Indexed: 11/13/2022] Open
Abstract
Phenotypic heterogeneity provides growth advantages for a population upon changes of the environment. In S. cerevisiae, such heterogeneity has been observed as "on/off" states in the expression of individual genes in individual cells. These variations can persist for a limited or extended number of mitotic divisions. Such traits are known to be mediated by heritable chromatin structures, by the mitotic transmission of transcription factors involved in gene regulatory circuits or by the cytoplasmic partition of prions or other unstructured proteins. The significance of such epigenetic diversity is obvious, however, we have limited insight into the mechanisms that generate it. In this review, we summarize the current knowledge of epigenetically maintained heterogeneity of gene expression and point out similarities and converging points between different mechanisms. We discuss how the sharing of limiting repression or activation factors can contribute to cell-to-cell variations in gene expression and to the coordination between short- and long- term epigenetic strategies. Finally, we discuss the implications of such variations and strategies in adaptation and aging.
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Affiliation(s)
- Kholoud Shaban
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada
| | - Safia Mahabub Sauty
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada
| | - Krassimir Yankulov
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada
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9
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Goffová I, Fajkus J. The rDNA Loci-Intersections of Replication, Transcription, and Repair Pathways. Int J Mol Sci 2021; 22:1302. [PMID: 33525595 PMCID: PMC7865372 DOI: 10.3390/ijms22031302] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 01/25/2021] [Accepted: 01/25/2021] [Indexed: 12/28/2022] Open
Abstract
Genes encoding ribosomal RNA (rDNA) are essential for cell survival and are particularly sensitive to factors leading to genomic instability. Their repetitive character makes them prone to inappropriate recombinational events arising from collision of transcriptional and replication machineries, resulting in unstable rDNA copy numbers. In this review, we summarize current knowledge on the structure and organization of rDNA, its role in sensing changes in the genome, and its linkage to aging. We also review recent findings on the main factors involved in chromatin assembly and DNA repair in the maintenance of rDNA stability in the model plants Arabidopsis thaliana and the moss Physcomitrella patens, providing a view across the plant evolutionary tree.
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Affiliation(s)
- Ivana Goffová
- Laboratory of Functional Genomics and Proteomics, National Centre for Biomolecular Research, Faculty of Science, Masaryk University, CZ-61137 Brno, Czech Republic;
- Chromatin Molecular Complexes, Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, CZ-62500 Brno, Czech Republic
| | - Jiří Fajkus
- Laboratory of Functional Genomics and Proteomics, National Centre for Biomolecular Research, Faculty of Science, Masaryk University, CZ-61137 Brno, Czech Republic;
- Chromatin Molecular Complexes, Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, CZ-62500 Brno, Czech Republic
- Department of Cell Biology and Radiobiology, Institute of Biophysics of the Czech Academy of Sciences, CZ-61265 Brno, Czech Republic
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10
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Mack EA, Tagliamonte MS, Xiao YP, Quesada S, Allred DR. Babesia bovis Rad51 ortholog influences switching of ves genes but is not essential for segmental gene conversion in antigenic variation. PLoS Pathog 2020; 16:e1008772. [PMID: 32866214 PMCID: PMC7485966 DOI: 10.1371/journal.ppat.1008772] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 09/11/2020] [Accepted: 08/13/2020] [Indexed: 01/04/2023] Open
Abstract
The tick-borne apicomplexan parasite, Babesia bovis, a highly persistent bovine pathogen, expresses VESA1 proteins on the infected erythrocyte surface to mediate cytoadhesion. The cytoadhesion ligand, VESA1, which protects the parasite from splenic passage, is itself protected from a host immune response by rapid antigenic variation. B. bovis relies upon segmental gene conversion (SGC) as a major mechanism to vary VESA1 structure. Gene conversion has been considered a form of homologous recombination (HR), a process for which Rad51 proteins are considered pivotal components. This could make BbRad51 a choice target for development of inhibitors that both interfere with parasite genome integrity and disrupt HR-dependent antigenic variation. Previously, we knocked out the Bbrad51 gene from the B. bovis haploid genome, resulting in a phenotype of sensitivity to methylmethane sulfonate (MMS) and apparent loss of HR-dependent integration of exogenous DNA. In a further characterization of BbRad51, we demonstrate here that ΔBbrad51 parasites are not more sensitive than wild-type to DNA damage induced by γ-irradiation, and repair their genome with similar kinetics. To assess the need for BbRad51 in SGC, RT-PCR was used to observe alterations to a highly variant region of ves1α transcripts over time. Mapping of these amplicons to the genome revealed a significant reduction of in situ transcriptional switching (isTS) among ves loci, but not cessation. By combining existing pipelines for analysis of the amplicons, we demonstrate that SGC continues unabated in ΔBbrad51 parasites, albeit at an overall reduced rate, and a reduction in SGC tract lengths was observed. By contrast, no differences were observed in the lengths of homologous sequences at which recombination occurred. These results indicate that, whereas BbRad51 is not essential to babesial antigenic variation, it influences epigenetic control of ves loci, and its absence significantly reduces successful variation. These results necessitate a reconsideration of the likely enzymatic mechanism(s) underlying SGC and suggest the existence of additional targets for development of small molecule inhibitors. B. bovis establishes highly persistent infections in cattle, in part by using cytoadhesion to avoid passage through the spleen. While protective, a host antibody response targeting the cytoadhesion ligand is quickly rendered ineffective by antigenic variation. In B. bovis, antigenic variation relies heavily upon segmental gene conversion (SGC), presumed to be a form of homologous recombination (HR), to generate variants. As Rad51 is generally considered essential to HR, we investigated its contribution to SGC. While diminishing the parasite’s capacity for HR-dependent integration of exogenous DNA, the loss of BbRad51 did not affect the parasite’s sensitivity to ionizing radiation, overall genome stability, or competence for SGC. Instead, loss of BbRad51 diminished the extent of in situ transcriptional switching (isTS) among ves gene loci, the accumulation of SGC recombinants, and the mean lengths of SGC sequence tracts. Given the overall reductions in VESA1 variability, compromise of the parasite’s capacity for in vivo persistence is predicted.
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Affiliation(s)
- Erin A. Mack
- Department of Infectious Diseases and Immunology, University of Florida, Gainesville, Florida, United States of America
| | - Massimiliano S. Tagliamonte
- Department of Pathology, Immunology, and Laboratory Medicine, University of Florida, Gainesville, Florida, United States of America
- Emerging Pathogens Institute, University of Florida, Gainesville, Florida, United States of America
| | - Yu-Ping Xiao
- Department of Infectious Diseases and Immunology, University of Florida, Gainesville, Florida, United States of America
| | - Samantha Quesada
- Department of Infectious Diseases and Immunology, University of Florida, Gainesville, Florida, United States of America
| | - David R. Allred
- Department of Infectious Diseases and Immunology, University of Florida, Gainesville, Florida, United States of America
- Department of Pathology, Immunology, and Laboratory Medicine, University of Florida, Gainesville, Florida, United States of America
- Emerging Pathogens Institute, University of Florida, Gainesville, Florida, United States of America
- Genetics Institute, University of Florida, Gainesville, Florida, United States of America
- * E-mail:
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11
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Spakman D, King GA, Peterman EJG, Wuite GJL. Constructing arrays of nucleosome positioning sequences using Gibson Assembly for single-molecule studies. Sci Rep 2020; 10:9903. [PMID: 32555215 PMCID: PMC7303147 DOI: 10.1038/s41598-020-66259-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Accepted: 04/24/2020] [Indexed: 01/08/2023] Open
Abstract
As the basic building blocks of chromatin, nucleosomes play a key role in dictating the accessibility of the eukaryotic genome. Consequently, nucleosomes are involved in essential genomic transactions such as DNA transcription, replication and repair. In order to unravel the mechanisms by which nucleosomes can influence, or be altered by, DNA-binding proteins, single-molecule techniques are increasingly employed. To this end, DNA molecules containing a defined series of nucleosome positioning sequences are often used to reconstitute arrays of nucleosomes in vitro. Here, we describe a novel method to prepare DNA molecules containing defined arrays of the ‘601’ nucleosome positioning sequence by exploiting Gibson Assembly cloning. The approaches presented here provide a more accessible and efficient means to generate arrays of nucleosome positioning motifs, and facilitate a high degree of control over the linker sequences between these motifs. Nucleosomes reconstituted on such arrays are ideal for interrogation with single-molecule techniques. To demonstrate this, we use dual-trap optical tweezers, in combination with fluorescence microscopy, to monitor nucleosome unwrapping and histone localisation as a function of tension. We reveal that, although nucleosomes unwrap at ~20 pN, histones (at least histone H3) remain bound to the DNA, even at tensions beyond 60 pN.
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Affiliation(s)
- Dian Spakman
- Department of Physics and Astronomy, and LaserLaB Amsterdam, Vrije Universiteit Amsterdam, De Boelelaan 1081, 1081 HV, Amsterdam, The Netherlands
| | - Graeme A King
- Department of Physics and Astronomy, and LaserLaB Amsterdam, Vrije Universiteit Amsterdam, De Boelelaan 1081, 1081 HV, Amsterdam, The Netherlands. .,Institute of Structural and Molecular Biology, University College London, Gower Street, London, WC1E 6BT, UK.
| | - Erwin J G Peterman
- Department of Physics and Astronomy, and LaserLaB Amsterdam, Vrije Universiteit Amsterdam, De Boelelaan 1081, 1081 HV, Amsterdam, The Netherlands.
| | - Gijs J L Wuite
- Department of Physics and Astronomy, and LaserLaB Amsterdam, Vrije Universiteit Amsterdam, De Boelelaan 1081, 1081 HV, Amsterdam, The Netherlands.
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12
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Rowlands H, Shaban K, Cheng A, Foster B, Yankulov K. Dysfunctional CAF-I reveals its role in cell cycle progression and differential regulation of gene silencing. Cell Cycle 2019; 18:3223-3236. [PMID: 31564230 DOI: 10.1080/15384101.2019.1673100] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Chromatin Assembly Factor I (CAF-I) plays a central role in the reassembly of H3/H4 histones during DNA replication. In S. cerevisiae CAF-I is not essential and its loss is associated with reduced gene silencing at telomeres and increased sensitivity to DNA damage. Two kinases, Cyclin Dependent Kinase (CDK) and Dbf4-Dependent Kinase (DDK), are known to phosphorylate the Cac1p subunit of CAF-I, but their role in the regulation of CAF-I activity is not well understood. In this study we systematically mutated the phosphorylation target sites of these kinases. We show that concomitant mutations of the CDK and DDK target sites of Cac1p lead to growth retardation and significant cell cycle defects, altered cell morphology and increased sensitivity to DNA damage. Surprisingly, some mutations also produced flocculation, a phenotype that is lost in most laboratory strains, and displayed elevated expression of FLO genes. None of these effects is observed upon the destruction of CAF-I. In contrast, the mutations that caused flocculation did not affect gene silencing at the mating type and subtelomeric loci. We conclude that dysfunctional CAF-I produces severe phenotypes, which reveal a possible role of CAF-I in the coordination of DNA replication, chromatin reassembly and cell cycle progression. Our study highlights the role of phosphorylation of Cac1p by CDK and a putative role for DDK in the transmission and re-assembly of chromatin during DNA replication.
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Affiliation(s)
- Hollie Rowlands
- Department of Molecular and Cellular Biology, University of Guelph , Guelph , Canada
| | - Kholoud Shaban
- Department of Molecular and Cellular Biology, University of Guelph , Guelph , Canada
| | - Ashley Cheng
- Department of Molecular and Cellular Biology, University of Guelph , Guelph , Canada
| | - Barret Foster
- Department of Molecular and Cellular Biology, University of Guelph , Guelph , Canada
| | - Krassimir Yankulov
- Department of Molecular and Cellular Biology, University of Guelph , Guelph , Canada
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13
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Rowlands H, Shaban K, Foster B, Proteau Y, Yankulov K. Histone chaperones and the Rrm3p helicase regulate flocculation in S. cerevisiae. Epigenetics Chromatin 2019; 12:56. [PMID: 31547833 PMCID: PMC6757361 DOI: 10.1186/s13072-019-0303-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2019] [Accepted: 09/03/2019] [Indexed: 12/16/2022] Open
Abstract
Background Biofilm formation or flocculation is a major phenotype in wild type budding yeasts but rarely seen in laboratory yeast strains. Here, we analysed flocculation phenotypes and the expression of FLO genes in laboratory strains with various genetic backgrounds. Results We show that mutations in histone chaperones, the helicase RRM3 and the Histone Deacetylase HDA1 de-repress the FLO genes and partially reconstitute flocculation. We demonstrate that the loss of repression correlates to elevated expression of several FLO genes, to increased acetylation of histones at the promoter of FLO1 and to variegated expression of FLO11. We show that these effects are related to the activity of CAF-1 at the replication forks. We also demonstrate that nitrogen starvation or inhibition of histone deacetylases do not produce flocculation in W303 and BY4742 strains but do so in strains compromised for chromatin maintenance. Finally, we correlate the de-repression of FLO genes to the loss of silencing at the subtelomeric and mating type gene loci. Conclusions We conclude that the deregulation of chromatin maintenance and transmission is sufficient to reconstitute flocculation in laboratory yeast strains. Consequently, we propose that a gain in epigenetic silencing is a major contributing factor for the loss of flocculation phenotypes in these strains. We suggest that flocculation in yeasts provides an excellent model for addressing the challenging issue of how epigenetic mechanisms contribute to evolution.
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Affiliation(s)
- Hollie Rowlands
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Canada
| | - Kholoud Shaban
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Canada
| | - Barret Foster
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Canada
| | - Yannic Proteau
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Canada
| | - Krassimir Yankulov
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Canada.
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14
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Liu Y, Siles L, Postigo A, Dean DC. Epigenetically distinct sister chromatids and asymmetric generation of tumor initiating cells. Cell Cycle 2018; 17:2221-2229. [PMID: 30290712 DOI: 10.1080/15384101.2018.1532254] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Cancer stem cells (CSC) are thought to be an important source of cancer cells in tumors of different origins. Mounting evidence suggests they are generated reversibly from existing cancer cells, and supply new cancer cells during tumor progression and following therapy. Elegant lineage mapping stud(ies are identifying progenitors, and in some cases differentiated cells, as targets of transformation in a variety of tumors. Recent evidence suggests resulting tumor initiating cells (TIC) might be distinct from CSC. Molecular pathways leading from cells of tumor origin to precancerous lesions and cancer cells are only beginning to be unraveled. We review a pathway where asymmetric division of precancerous cells generates TIC in a K-Ras-initiated model of lung cancer. And, we compare unexpected steps in this asymmetric division to those evident in well-studied stem cell models.
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Affiliation(s)
- Yongqing Liu
- a Molecular Targets Program , James Graham Brown Cancer Center , Louisville , Kentucky.,b Department of Ophthalmology and Visual Sciences.,c Birth Defects Center , University of Louisville Health Sciences Center
| | - Laura Siles
- d Group of Transcriptional Regulation of Gene Expression , Institut d'Investigacions BiomèdiquesAugust Pi i Sunyer (IDIBAPS) , Barcelona , Spain
| | - Antonio Postigo
- a Molecular Targets Program , James Graham Brown Cancer Center , Louisville , Kentucky.,d Group of Transcriptional Regulation of Gene Expression , Institut d'Investigacions BiomèdiquesAugust Pi i Sunyer (IDIBAPS) , Barcelona , Spain.,e ICREA , Barcelona , Spain
| | - Douglas C Dean
- a Molecular Targets Program , James Graham Brown Cancer Center , Louisville , Kentucky.,b Department of Ophthalmology and Visual Sciences.,c Birth Defects Center , University of Louisville Health Sciences Center
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15
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Falk M, Falková I, Kopečná O, Bačíková A, Pagáčová E, Šimek D, Golan M, Kozubek S, Pekarová M, Follett SE, Klejdus B, Elliott KW, Varga K, Teplá O, Kratochvílová I. Chromatin architecture changes and DNA replication fork collapse are critical features in cryopreserved cells that are differentially controlled by cryoprotectants. Sci Rep 2018; 8:14694. [PMID: 30279538 PMCID: PMC6168476 DOI: 10.1038/s41598-018-32939-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Accepted: 09/17/2018] [Indexed: 11/22/2022] Open
Abstract
In this work, we shed new light on the highly debated issue of chromatin fragmentation in cryopreserved cells. Moreover, for the first time, we describe replicating cell-specific DNA damage and higher-order chromatin alterations after freezing and thawing. We identified DNA structural changes associated with the freeze-thaw process and correlated them with the viability of frozen and thawed cells. We simultaneously evaluated DNA defects and the higher-order chromatin structure of frozen and thawed cells with and without cryoprotectant treatment. We found that in replicating (S phase) cells, DNA was preferentially damaged by replication fork collapse, potentially leading to DNA double strand breaks (DSBs), which represent an important source of both genome instability and defects in epigenome maintenance. This induction of DNA defects by the freeze-thaw process was not prevented by any cryoprotectant studied. Both in replicating and non-replicating cells, freezing and thawing altered the chromatin structure in a cryoprotectant-dependent manner. Interestingly, cells with condensed chromatin, which was strongly stimulated by dimethyl sulfoxide (DMSO) prior to freezing had the highest rate of survival after thawing. Our results will facilitate the design of compounds and procedures to decrease injury to cryopreserved cells.
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Affiliation(s)
- Martin Falk
- The Czech Academy of Sciences, Institute of Biophysics, Královopolská 135, CZ-612 65, Brno, Czech Republic.
| | - Iva Falková
- The Czech Academy of Sciences, Institute of Biophysics, Královopolská 135, CZ-612 65, Brno, Czech Republic
| | - Olga Kopečná
- The Czech Academy of Sciences, Institute of Biophysics, Královopolská 135, CZ-612 65, Brno, Czech Republic
| | - Alena Bačíková
- The Czech Academy of Sciences, Institute of Biophysics, Královopolská 135, CZ-612 65, Brno, Czech Republic
| | - Eva Pagáčová
- The Czech Academy of Sciences, Institute of Biophysics, Královopolská 135, CZ-612 65, Brno, Czech Republic
| | - Daniel Šimek
- The Czech Academy of Sciences, Institute of Physics, Na Slovance 2, CZ-182 21, Prague 8, Czech Republic
| | - Martin Golan
- The Czech Academy of Sciences, Institute of Physics, Na Slovance 2, CZ-182 21, Prague 8, Czech Republic
- Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 5, Prague 2, CZ-121 16, Czech Republic
| | - Stanislav Kozubek
- The Czech Academy of Sciences, Institute of Biophysics, Královopolská 135, CZ-612 65, Brno, Czech Republic
| | - Michaela Pekarová
- The Czech Academy of Sciences, Institute of Biophysics, Královopolská 135, CZ-612 65, Brno, Czech Republic
| | - Shelby E Follett
- Department of Chemistry, University of Wyoming, 1000 E. University Ave, WY 82071, Laramie, USA
| | - Bořivoj Klejdus
- Institute of Chemistry and Biochemistry, Faculty of Agronomy, Mendel University in Brno, Zemědělská 1, CZ-613 00, Czech Republic
- CEITEC-Central European Institute of Technology, Mendel University in Brno, Zemědělská 1, CZ-613 00, Brno, Czech Republic
| | - K Wade Elliott
- Department of Molecular, Cellular, and Biomedical Sciences, University of New Hampshire, 46 College Road, Durham, NH, 03824, USA
| | - Krisztina Varga
- Department of Molecular, Cellular, and Biomedical Sciences, University of New Hampshire, 46 College Road, Durham, NH, 03824, USA
| | - Olga Teplá
- ISCARE IVF a.s, Jankovcova 1692, CZ-160 00, Praha 6, Czech Republic
- VFN Gynekologicko-porodnická klinika, Apolinářská 18, CZ-120 00, Czech Republic
| | - Irena Kratochvílová
- The Czech Academy of Sciences, Institute of Physics, Na Slovance 2, CZ-182 21, Prague 8, Czech Republic.
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