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Pytko KG, Dannenberg RL, Eckert KA, Hedglin M. Replication of [AT/TA] 25 Microsatellite Sequences by Human DNA Polymerase δ Holoenzymes Is Dependent on dNTP and RPA Levels. Biochemistry 2024; 63:969-983. [PMID: 38623046 DOI: 10.1021/acs.biochem.4c00006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/17/2024]
Abstract
Fragile sites are unstable genomic regions that are prone to breakage during stressed DNA replication. Several common fragile sites (CFS) contain A+T-rich regions including perfect [AT/TA] microsatellite repeats that may collapse into hairpins when in single-stranded DNA (ssDNA) form and coincide with chromosomal hotspots for breakage and rearrangements. While many factors contribute to CFS instability, evidence exists for replication stalling within [AT/TA] microsatellite repeats. Currently, it is unknown how stress causes replication stalling within [AT/TA] microsatellite repeats. To investigate this, we utilized FRET to characterize the structures of [AT/TA]25 sequences and also reconstituted lagging strand replication to characterize the progression of pol δ holoenzymes through A+T-rich sequences. The results indicate that [AT/TA]25 sequences adopt hairpins that are unwound by the major ssDNA-binding complex, RPA, and the progression of pol δ holoenzymes through A+T-rich sequences saturated with RPA is dependent on the template sequence and dNTP concentration. Importantly, the effects of RPA on the replication of [AT/TA]25 sequences are dependent on dNTP concentration, whereas the effects of RPA on the replication of A+T-rich, nonstructure-forming sequences are independent of dNTP concentration. Collectively, these results reveal complexities in lagging strand replication and provide novel insights into how [AT/TA] microsatellite repeats contribute to genome instability.
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Affiliation(s)
- Kara G Pytko
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, United States
| | - Rachel L Dannenberg
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, United States
| | - Kristin A Eckert
- Department of Pathology and Laboratory Medicine, The Jake Gittlen Laboratories for Cancer Research, Hershey, PA 17033, United States
| | - Mark Hedglin
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, United States
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Pytko KG, Dannenberg RL, Eckert KA, Hedglin M. Replication of [AT/TA] 25 microsatellite sequences by human DNA polymerase δ holoenzymes is dependent on dNTP and RPA levels. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.07.566133. [PMID: 37986888 PMCID: PMC10659299 DOI: 10.1101/2023.11.07.566133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
Difficult-to-Replicate Sequences (DiToRS) are natural impediments in the human genome that inhibit DNA replication under endogenous replication. Some of the most widely-studied DiToRS are A+T-rich, high "flexibility regions," including long stretches of perfect [AT/TA] microsatellite repeats that have the potential to collapse into hairpin structures when in single-stranded DNA (ssDNA) form and are sites of recurrent structural variation and double-stranded DNA (dsDNA) breaks. Currently, it is unclear how these flexibility regions impact DNA replication, greatly limiting our fundamental understanding of human genome stability. To investigate replication through flexibility regions, we utilized FRET to characterize the effects of the major ssDNA-binding complex, RPA, on the structure of perfect [AT/TA]25 microsatellite repeats and also re-constituted human lagging strand replication to quantitatively characterize initial encounters of pol δ holoenzymes with A+T-rich DNA template sequences. The results indicate that [AT/TA]25 sequences adopt hairpin structures that are unwound by RPA and pol δ holoenzymes support dNTP incorporation through the [AT/TA]25 sequences as well as an A+T-rich, non-structure forming sequence. Furthermore, the extent of dNTP incorporation is dependent on the sequence of the DNA template and the concentration of dNTPs. Importantly, the effects of RPA on the replication of [AT/TA]25 sequences are dependent on the concentration of dNTPs, whereas the effects of RPA on the replication of an A+T-rich, non-structure forming sequence are independent of dNTP concentration. Collectively, these results reveal complexities in lagging strand replication and provide novel insights into how flexibility regions contribute to genome instability.
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Affiliation(s)
- Kara G. Pytko
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802
| | - Rachel L. Dannenberg
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802
| | - Kristin A. Eckert
- Department of Pathology and Laboratory Medicine, The Jake Gittlen Laboratories for Cancer Research, Hershey, PA 17033
| | - Mark Hedglin
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802
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Kodali S, Meyer-Nava S, Landry S, Chakraborty A, Rivera-Mulia JC, Feng W. Epigenomic signatures associated with spontaneous and replication stress-induced DNA double strand breaks. Front Genet 2022; 13:907547. [PMID: 36506300 PMCID: PMC9730818 DOI: 10.3389/fgene.2022.907547] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Accepted: 11/07/2022] [Indexed: 11/25/2022] Open
Abstract
Common fragile sites (CFSs) are specific regions of all individuals' genome that are predisposed to DNA double strand breaks (DSBs) and undergo subsequent rearrangements. CFS formation can be induced in vitro by mild level of DNA replication stress, such as DNA polymerase inhibition or nucleotide pool disturbance. The mechanisms of CFS formation have been linked to DNA replication timing control, transcription activities, as well as chromatin organization. However, it is unclear what specific cis- or trans-factors regulate the interplay between replication and transcription that determine CFS formation. We recently reported genome-wide mapping of DNA DSBs under replication stress induced by aphidicolin in human lymphoblastoids for the first time. Here, we systematically compared these DSBs with regards to nearby epigenomic features mapped in the same cell line from published studies. We demonstrate that aphidicolin-induced DSBs are strongly correlated with histone 3 lysine 36 trimethylation, a marker for active transcription. We further demonstrate that this DSB signature is a composite effect by the dual treatment of aphidicolin and its solvent, dimethylsulfoxide, the latter of which potently induces transcription on its own. We also present complementing evidence for the association between DSBs and 3D chromosome architectural domains with high density gene cluster and active transcription. Additionally, we show that while DSBs were detected at all but one of the fourteen finely mapped CFSs, they were not enriched in the CFS core sequences and rather demarcated the CFS core region. Related to this point, DSB density was not higher in large genes of greater than 300 kb, contrary to reported enrichment of CFS sites at these large genes. Finally, replication timing analyses demonstrate that the CFS core region contain initiation events, suggesting that altered replication dynamics are responsible for CFS formation in relatively higher level of replication stress.
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Affiliation(s)
- Sravan Kodali
- Department of Biochemistry and Molecular Biology, Upstate Medical University, Syracuse, NY, United States
| | - Silvia Meyer-Nava
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, United States
| | - Stephen Landry
- Department of Biochemistry and Molecular Biology, Upstate Medical University, Syracuse, NY, United States
| | - Arijita Chakraborty
- Department of Biochemistry and Molecular Biology, Upstate Medical University, Syracuse, NY, United States
| | - Juan Carlos Rivera-Mulia
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, United States
| | - Wenyi Feng
- Department of Biochemistry and Molecular Biology, Upstate Medical University, Syracuse, NY, United States
- *Correspondence: Wenyi Feng,
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Ben Yamin B, Ahmed-Seghir S, Tomida J, Despras E, Pouvelle C, Yurchenko A, Goulas J, Corre R, Delacour Q, Droin N, Dessen P, Goidin D, Lange SS, Bhetawal S, Mitjavila-Garcia MT, Baldacci G, Nikolaev S, Cadoret JC, Wood RD, Kannouche PL. DNA polymerase zeta contributes to heterochromatin replication to prevent genome instability. EMBO J 2021; 40:e104543. [PMID: 34533226 PMCID: PMC8561639 DOI: 10.15252/embj.2020104543] [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: 01/22/2020] [Revised: 08/20/2021] [Accepted: 08/28/2021] [Indexed: 02/06/2023] Open
Abstract
The DNA polymerase zeta (Polζ) plays a critical role in bypassing DNA damage. REV3L, the catalytic subunit of Polζ, is also essential in mouse embryonic development and cell proliferation for reasons that remain incompletely understood. In this study, we reveal that REV3L protein interacts with heterochromatin components including repressive histone marks and localizes in pericentromeric regions through direct interaction with HP1 dimer. We demonstrate that Polζ/REV3L ensures progression of replication forks through difficult‐to‐replicate pericentromeric heterochromatin, thereby preventing spontaneous chromosome break formation. We also find that Rev3l‐deficient cells are compromised in the repair of heterochromatin‐associated double‐stranded breaks, eliciting deletions in late‐replicating regions. Lack of REV3L leads to further consequences that may be ascribed to heterochromatin replication and repair‐associated functions of Polζ, with a disruption of the temporal replication program at specific loci. This is correlated with changes in epigenetic landscape and transcriptional control of developmentally regulated genes. These results reveal a new function of Polζ in preventing chromosome instability during replication of heterochromatic regions.
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Affiliation(s)
- Barbara Ben Yamin
- CNRS-UMR9019, Equipe labellisée Ligue Contre le Cancer, Gustave Roussy, Paris-Saclay Université, Villejuif, France
| | - Sana Ahmed-Seghir
- CNRS-UMR9019, Equipe labellisée Ligue Contre le Cancer, Gustave Roussy, Paris-Saclay Université, Villejuif, France
| | - Junya Tomida
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center and The University of Texas MD Anderson Cancer Center UT Health Graduate School of Biomedical Sciences, Houston, TX, USA
| | - Emmanuelle Despras
- CNRS-UMR9019, Equipe labellisée Ligue Contre le Cancer, Gustave Roussy, Paris-Saclay Université, Villejuif, France
| | - Caroline Pouvelle
- CNRS-UMR9019, Equipe labellisée Ligue Contre le Cancer, Gustave Roussy, Paris-Saclay Université, Villejuif, France
| | - Andrey Yurchenko
- INSERM U981, Gustave Roussy, Université Paris Saclay, Villejuif, France
| | - Jordane Goulas
- CNRS-UMR9019, Equipe labellisée Ligue Contre le Cancer, Gustave Roussy, Paris-Saclay Université, Villejuif, France
| | - Raphael Corre
- CNRS-UMR9019, Equipe labellisée Ligue Contre le Cancer, Gustave Roussy, Paris-Saclay Université, Villejuif, France
| | - Quentin Delacour
- CNRS-UMR9019, Equipe labellisée Ligue Contre le Cancer, Gustave Roussy, Paris-Saclay Université, Villejuif, France
| | | | - Philippe Dessen
- Bioinformatics Core Facility, Gustave Roussy, Villejuif, France
| | - Didier Goidin
- Life Sciences and Diagnostics Group, Agilent Technologies France, Les Ulis, France
| | - Sabine S Lange
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center and The University of Texas MD Anderson Cancer Center UT Health Graduate School of Biomedical Sciences, Houston, TX, USA
| | - Sarita Bhetawal
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center and The University of Texas MD Anderson Cancer Center UT Health Graduate School of Biomedical Sciences, Houston, TX, USA
| | | | - Giuseppe Baldacci
- Institut Jacques Monod, UMR7592, CNRS and University of Paris, Paris, France
| | - Sergey Nikolaev
- INSERM U981, Gustave Roussy, Université Paris Saclay, Villejuif, France
| | | | - Richard D Wood
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center and The University of Texas MD Anderson Cancer Center UT Health Graduate School of Biomedical Sciences, Houston, TX, USA
| | - Patricia L Kannouche
- CNRS-UMR9019, Equipe labellisée Ligue Contre le Cancer, Gustave Roussy, Paris-Saclay Université, Villejuif, France
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Irony-Tur Sinai M, Salamon A, Stanleigh N, Goldberg T, Weiss A, Wang YH, Kerem B. AT-dinucleotide rich sequences drive fragile site formation. Nucleic Acids Res 2019; 47:9685-9695. [PMID: 31410468 PMCID: PMC6765107 DOI: 10.1093/nar/gkz689] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 07/18/2019] [Accepted: 08/04/2019] [Indexed: 12/29/2022] Open
Abstract
Common fragile sites (CFSs) are genomic regions prone to breakage under replication stress conditions recurrently rearranged in cancer. Many CFSs are enriched with AT-dinucleotide rich sequences (AT-DRSs) which have the potential to form stable secondary structures upon unwinding the double helix during DNA replication. These stable structures can potentially perturb DNA replication progression, leading to genomic instability. Using site-specific targeting system, we show that targeted integration of a 3.4 kb AT-DRS derived from the human CFS FRA16C into a chromosomally stable region within the human genome is able to drive fragile site formation under conditions of replication stress. Analysis of >1300 X chromosomes integrated with the 3.4 kb AT-DRS revealed recurrent gaps and breaks at the integration site. DNA sequences derived from the integrated AT-DRS showed in vitro a significantly increased tendency to fold into branched secondary structures, supporting the predicted mechanism of instability. Our findings clearly indicate that intrinsic DNA features, such as complexed repeated sequence motifs, predispose the human genome to chromosomal instability.
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Affiliation(s)
- Michal Irony-Tur Sinai
- Department of Genetics, The Life Sciences Institute, The Hebrew University of Jerusalem, 9190401, Israel
| | - Anita Salamon
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, Virginia, 229080733, USA
| | - Noemie Stanleigh
- Department of Genetics, The Life Sciences Institute, The Hebrew University of Jerusalem, 9190401, Israel
| | - Tchelet Goldberg
- Department of Genetics, The Life Sciences Institute, The Hebrew University of Jerusalem, 9190401, Israel
| | - Aryeh Weiss
- Faculty of Engineering, Bar-Ilan University, Ramat-Gan, 52900, Israel
| | - Yuh-Hwa Wang
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, Virginia, 229080733, USA
| | - Batsheva Kerem
- Department of Genetics, The Life Sciences Institute, The Hebrew University of Jerusalem, 9190401, Israel
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6
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Palumbo E, Russo A. Common fragile site instability in normal cells: Lessons and perspectives. Genes Chromosomes Cancer 2018; 58:260-269. [PMID: 30387295 DOI: 10.1002/gcc.22705] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Revised: 09/25/2018] [Accepted: 10/01/2018] [Indexed: 12/26/2022] Open
Abstract
Mechanisms and events related to common fragile site (CFS) instability are well known in cancer cells. Here, we argue that normal cells remain an important experimental model to address questions related to CFS instability in the absence of alterations in cell cycle and DNA damage repair pathways, which are common features acquired in cancer. Furthermore, a major gap of knowledge concerns the stability of CFSs during gametogenesis. CFS instability in meiotic or postmeiotic stages of the germ cell line could generate chromosome deletions or large rearrangements. This in turn can lead to the functional loss of the several CFS-associated genes with tumor suppressor function. Our hypothesis is that such mutations can potentially result in genetic predisposition to develop cancer. Indirect evidence for CFS instability in human germ cells has been provided by genomic investigations in family pedigrees associated with genetic disease. The issue of CFS instability in the germ cell line should represent one of the future efforts, and may take advantage of the existence of sequence and functional conservation of CFSs between rodents and humans.
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Affiliation(s)
- Elisa Palumbo
- Department of Molecular Medicine, University of Padova, Padova, Italy
| | - Antonella Russo
- Department of Molecular Medicine, University of Padova, Padova, Italy
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7
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Zheglo D, Brueckner LM, Sepman O, Wecht EM, Kuligina E, Suspitsin E, Imyanitov E, Savelyeva L. The FRA14B
common fragile site maps to a region prone to somatic and germline rearrangements within the large GPHN
gene. Genes Chromosomes Cancer 2018; 58:284-294. [DOI: 10.1002/gcc.22706] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Revised: 10/31/2018] [Accepted: 11/01/2018] [Indexed: 01/27/2023] Open
Affiliation(s)
- Diana Zheglo
- FSBI Research Centre for Medical Genetics; Moscow Russia
| | - Lena M. Brueckner
- Division of Neuroblastoma Genomics; German Cancer Research Center (DKFZ); Heidelberg Germany
| | - Olga Sepman
- Klinik fuer Allgemein-, Viszeral-, Thorax- und minimal-invasive Chirurgie; Pforzheim Germany
| | - Elisa M. Wecht
- Division of Neuroblastoma Genomics; German Cancer Research Center (DKFZ); Heidelberg Germany
| | | | - Evgenij Suspitsin
- Petrov Institute of Oncology; St Petersburg Russia
- St. Petersburg Pediatric Medical University; Sankt-Peterburg Russia
| | - Evgenij Imyanitov
- Petrov Institute of Oncology; St Petersburg Russia
- Mechnikov North-Western Medical University; Saint Petersburg Russia
| | - Larissa Savelyeva
- Division of Neuroblastoma Genomics; German Cancer Research Center (DKFZ); Heidelberg Germany
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8
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Saldivar JC, Park D. Mechanisms shaping the mutational landscape of the FRA3B/FHIT-deficient cancer genome. Genes Chromosomes Cancer 2018; 58:317-323. [PMID: 30242938 DOI: 10.1002/gcc.22684] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Accepted: 09/16/2018] [Indexed: 12/20/2022] Open
Abstract
Genome instability is an enabling characteristic of cancer that facilitates the acquisition of oncogenic mutations that drive tumorigenesis. Underlying much of the instability in cancer is DNA replication stress, which causes both chromosome structural changes and single base-pair mutations. Common fragile sites are some of the earliest and most frequently altered loci in tumors. Notably, the fragile locus, FRA3B, lies within the fragile histidine triad (FHIT) gene, and consequently deletions within FHIT are common in cancer. We review the evidence in support of FHIT as a DNA caretaker and discuss the mechanism by which FHIT promotes genome stability. FHIT increases thymidine kinase 1 (TK1) translation to balance the deoxyribonucleotide triphosphates (dNTPs) for efficient DNA replication. Consequently, FHIT-loss causes replication stress, DNA breaks, aneuploidy, copy-number changes (CNCs), small insertions and deletions, and point mutations. Moreover, FHIT-loss-induced replication stress and DNA breaks cooperate with APOBEC3B overexpression to catalyze DNA hypermutation in cancer, as APOBEC family enzymes prefer single-stranded DNA (ssDNA) as substrates and ssDNA is enriched at sites of both replication stress and DNA breaks. Consistent with the frequent loss of FHIT across a broad spectrum of cancer types, FHIT-deficiency is highly associated with the ubiquitous, clock-like mutation signature 5 occurring in all cancer types thus far examined. The ongoing destabilization of the genome caused by FHIT loss underlies recurrent inactivation of tumor suppressors and activation of oncogenes. Considering that more than 50% of cancers are FHIT-deficient, we propose that FRA3B/FHIT fragility shapes the mutational landscape of cancer genomes.
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Affiliation(s)
- Joshua C Saldivar
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, California
| | - Dongju Park
- Department of Cancer Biology and Genetics, The Ohio State University, Comprehensive Cancer Center, Columbus, Ohio
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Dynamic changes in ORC localization and replication fork progression during tissue differentiation. BMC Genomics 2018; 19:623. [PMID: 30134926 PMCID: PMC6103881 DOI: 10.1186/s12864-018-4992-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Accepted: 08/02/2018] [Indexed: 12/23/2022] Open
Abstract
Background Genomic regions repressed for DNA replication, resulting in either delayed replication in S phase or underreplication in polyploid cells, are thought to be controlled by inhibition of replication origin activation. Studies in Drosophila polytene cells, however, raised the possibility that impeding replication fork progression also plays a major role. Results We exploited genomic regions underreplicated (URs) with tissue specificity in Drosophila polytene cells to analyze mechanisms of replication repression. By localizing the Origin Recognition Complex (ORC) in the genome of the larval fat body and comparing this to ORC binding in the salivary gland, we found that sites of ORC binding show extensive tissue specificity. In contrast, there are common domains nearly devoid of ORC in the salivary gland and fat body that also have reduced density of ORC binding sites in diploid cells. Strikingly, domains lacking ORC can still be replicated in some polytene tissues, showing absence of ORC and origins is insufficient to repress replication. Analysis of the width and location of the URs with respect to ORC position indicates that whether or not a genomic region lacking ORC is replicated is controlled by whether replication forks formed outside the region are inhibited. Conclusions These studies demonstrate that inhibition of replication fork progression can block replication across genomic regions that constitutively lack ORC. Replication fork progression can be inhibited in both tissue-specific and genome region-specific ways. Consequently, when evaluating sources of genome instability it is important to consider altered control of replication forks in response to differentiation. Electronic supplementary material The online version of this article (10.1186/s12864-018-4992-3) contains supplementary material, which is available to authorized users.
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DNA Replication Control During Drosophila Development: Insights into the Onset of S Phase, Replication Initiation, and Fork Progression. Genetics 2017; 207:29-47. [PMID: 28874453 PMCID: PMC5586379 DOI: 10.1534/genetics.115.186627] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Accepted: 05/19/2017] [Indexed: 12/11/2022] Open
Abstract
Proper control of DNA replication is critical to ensure genomic integrity during cell proliferation. In addition, differential regulation of the DNA replication program during development can change gene copy number to influence cell size and gene expression. Drosophila melanogaster serves as a powerful organism to study the developmental control of DNA replication in various cell cycle contexts in a variety of differentiated cell and tissue types. Additionally, Drosophila has provided several developmentally regulated replication models to dissect the molecular mechanisms that underlie replication-based copy number changes in the genome, which include differential underreplication and gene amplification. Here, we review key findings and our current understanding of the developmental control of DNA replication in the contexts of the archetypal replication program as well as of underreplication and differential gene amplification. We focus on the use of these latter two replication systems to delineate many of the molecular mechanisms that underlie the developmental control of replication initiation and fork elongation.
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11
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Blumenfeld B, Ben-Zimra M, Simon I. Perturbations in the Replication Program Contribute to Genomic Instability in Cancer. Int J Mol Sci 2017; 18:E1138. [PMID: 28587102 PMCID: PMC5485962 DOI: 10.3390/ijms18061138] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Revised: 05/08/2017] [Accepted: 05/21/2017] [Indexed: 12/14/2022] Open
Abstract
Cancer and genomic instability are highly impacted by the deoxyribonucleic acid (DNA) replication program. Inaccuracies in DNA replication lead to the increased acquisition of mutations and structural variations. These inaccuracies mainly stem from loss of DNA fidelity due to replication stress or due to aberrations in the temporal organization of the replication process. Here we review the mechanisms and impact of these major sources of error to the replication program.
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Affiliation(s)
- Britny Blumenfeld
- Department of Microbiology and Molecular Genetics, IMRIC, Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem 91120, Israel.
| | - Micha Ben-Zimra
- Department of Microbiology and Molecular Genetics, IMRIC, Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem 91120, Israel.
- Pharmacology and Experimental Therapeutics Unit, The Institute for Drug Research, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem 91120, Israel.
| | - Itamar Simon
- Department of Microbiology and Molecular Genetics, IMRIC, Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem 91120, Israel.
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12
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Abstract
Genomic instability is a hallmark of cancer and a common feature of human disorders, characterized by growth defects, neurodegeneration, cancer predisposition, and aging. Recent evidence has shown that DNA replication stress is a major driver of genomic instability and tumorigenesis. Cells can undergo mitosis with under-replicated DNA or unresolved DNA structures, and specific pathways are dedicated to resolving these structures during mitosis, suggesting that mitotic rescue from replication stress (MRRS) is a key process influencing genome stability and cellular homeostasis. Deregulation of MRRS following oncogene activation or loss-of-function of caretaker genes may be the cause of chromosomal aberrations that promote cancer initiation and progression. In this review, we discuss the causes and consequences of replication stress, focusing on its persistence in mitosis as well as the mechanisms and factors involved in its resolution, and the potential impact of incomplete replication or aberrant MRRS on tumorigenesis, aging and disease.
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Affiliation(s)
- Michalis Fragkos
- a CNRS UMR8200 , University Paris-Saclay , Gustave Roussy, Villejuif , France
| | - Valeria Naim
- a CNRS UMR8200 , University Paris-Saclay , Gustave Roussy, Villejuif , France
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13
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Aladjem MI, Redon CE. Order from clutter: selective interactions at mammalian replication origins. Nat Rev Genet 2017; 18:101-116. [PMID: 27867195 PMCID: PMC6596300 DOI: 10.1038/nrg.2016.141] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Mammalian chromosome duplication progresses in a precise order and is subject to constraints that are often relaxed in developmental disorders and malignancies. Molecular information about the regulation of DNA replication at the chromatin level is lacking because protein complexes that initiate replication seem to bind chromatin indiscriminately. High-throughput sequencing and mathematical modelling have yielded detailed genome-wide replication initiation maps. Combining these maps and models with functional genetic analyses suggests that distinct DNA-protein interactions at subgroups of replication initiation sites (replication origins) modulate the ubiquitous replication machinery and supports an emerging model that delineates how indiscriminate DNA-binding patterns translate into a consistent, organized replication programme.
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Affiliation(s)
- Mirit I Aladjem
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, 37 Convent Drive, Bethesda, Maryland 20892, USA
| | - Christophe E Redon
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, 37 Convent Drive, Bethesda, Maryland 20892, USA
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14
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Cyclin E Deregulation and Genomic Instability. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1042:527-547. [PMID: 29357072 DOI: 10.1007/978-981-10-6955-0_22] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Precise replication of genetic material and its equal distribution to daughter cells are essential to maintain genome stability. In eukaryotes, chromosome replication and segregation are temporally uncoupled, occurring in distinct intervals of the cell cycle, S and M phases, respectively. Cyclin E accumulates at the G1/S transition, where it promotes S phase entry and progression by binding to and activating CDK2. Several lines of evidence from different models indicate that cyclin E/CDK2 deregulation causes replication stress in S phase and chromosome segregation errors in M phase, leading to genomic instability and cancer. In this chapter, we will discuss the main findings that link cyclin E/CDK2 deregulation to genomic instability and the molecular mechanisms by which cyclin E/CDK2 induces replication stress and chromosome aberrations during carcinogenesis.
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15
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Feng W, Chakraborty A. Fragility Extraordinaire: Unsolved Mysteries of Chromosome Fragile Sites. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1042:489-526. [PMID: 29357071 DOI: 10.1007/978-981-10-6955-0_21] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Chromosome fragile sites are a fascinating cytogenetic phenomenon now widely implicated in a slew of human diseases ranging from neurological disorders to cancer. Yet, the paths leading to these revelations were far from direct, and the number of fragile sites that have been molecularly cloned with known disease-associated genes remains modest. Moreover, as more fragile sites were being discovered, research interests in some of the earliest discovered fragile sites ebbed away, leaving a number of unsolved mysteries in chromosome biology. In this review we attempt to recount some of the early discoveries of fragile sites and highlight those phenomena that have eluded intense scrutiny but remain extremely relevant in our understanding of the mechanisms of chromosome fragility. We then survey the literature for disease association for a comprehensive list of fragile sites. We also review recent studies addressing the underlying cause of chromosome fragility while highlighting some ongoing debates. We report an observed enrichment for R-loop forming sequences in fragile site-associated genes than genomic average. Finally, we will leave the reader with some lingering questions to provoke discussion and inspire further scientific inquiries.
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Affiliation(s)
- Wenyi Feng
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, USA.
| | - Arijita Chakraborty
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, USA
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Hazan I, Hofmann TG, Aqeilan RI. Tumor Suppressor Genes within Common Fragile Sites Are Active Players in the DNA Damage Response. PLoS Genet 2016; 12:e1006436. [PMID: 27977694 PMCID: PMC5157955 DOI: 10.1371/journal.pgen.1006436] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The role of common fragile sites (CFSs) in cancer remains controversial. Two main views dominate the discussion: one suggests that CFS loci are hotspots of genomic instability leading to inactivation of genes encoded within them, while the other view proposes that CFSs are functional units and that loss of the encoded genes confers selective pressure, leading to cancer development. The latter view is supported by emerging evidence showing that expression of a given CFS is associated with genome integrity and that inactivation of CFS-resident tumor suppressor genes leads to dysregulation of the DNA damage response (DDR) and increased genomic instability. These two viewpoints of CFS function are not mutually exclusive but rather coexist; when breaks at CFSs are not repaired accurately, this can lead to deletions by which cells acquire growth advantage because of loss of tumor suppressor activities. Here, we review recent advances linking some CFS gene products with the DDR, genomic instability, and carcinogenesis and discuss how their inactivation might represent a selective advantage for cancer cells.
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Affiliation(s)
- Idit Hazan
- Lautenberg Center for Immunology and Cancer Research, IMRIC, Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Thomas G. Hofmann
- Cellular Senescence Group, Department of Epigenetics, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Rami I. Aqeilan
- Lautenberg Center for Immunology and Cancer Research, IMRIC, Hebrew University-Hadassah Medical School, Jerusalem, Israel
- Department of Cancer Biology and Genetics, The Ohio State University Wexner Medical Center, Columbus, Ohio, United States of America
- Department of Biochemistry, University of Vermont College of Medicine, Burlington, Vermont, United States of America
- * E-mail:
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17
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Zofall M, Smith DR, Mizuguchi T, Dhakshnamoorthy J, Grewal SIS. Taz1-Shelterin Promotes Facultative Heterochromatin Assembly at Chromosome-Internal Sites Containing Late Replication Origins. Mol Cell 2016; 62:862-874. [PMID: 27264871 DOI: 10.1016/j.molcel.2016.04.034] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2015] [Revised: 03/07/2016] [Accepted: 04/28/2016] [Indexed: 10/21/2022]
Abstract
Facultative heterochromatin regulates gene expression, but its assembly is poorly understood. Previously, we identified facultative heterochromatin islands in the fission yeast genome and found that RNA elimination machinery promotes island assembly at meiotic genes. Here, we report that Taz1, a component of the telomere protection complex Shelterin, is required to assemble heterochromatin islands at regions corresponding to late replication origins that are sites of double-strand break formation during meiosis. The loss of Taz1 or other Shelterin subunits, including Ccq1 that interacts with Clr4/Suv39h, abolishes heterochromatin at late origins and causes derepression of associated genes. Moreover, the late-origin regulator Rif1 affects heterochromatin at Taz1-dependent islands and subtelomeric regions. We explore the connection between facultative heterochromatin and replication control and show that heterochromatin machinery affects replication timing. These analyses reveal the role of Shelterin in facultative heterochromatin assembly at late origins, which has important implications for genome stability and gene regulation.
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Affiliation(s)
- Martin Zofall
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Deborah R Smith
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Takeshi Mizuguchi
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jothy Dhakshnamoorthy
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Shiv I S Grewal
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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18
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Petrakis TG, Komseli ES, Papaioannou M, Vougas K, Polyzos A, Myrianthopoulos V, Mikros E, Trougakos IP, Thanos D, Branzei D, Townsend P, Gorgoulis VG. Exploring and exploiting the systemic effects of deregulated replication licensing. Semin Cancer Biol 2016; 37-38:3-15. [PMID: 26707000 DOI: 10.1016/j.semcancer.2015.12.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Revised: 12/10/2015] [Accepted: 12/15/2015] [Indexed: 02/07/2023]
Abstract
Maintenance and accurate propagation of the genetic material are key features for physiological development and wellbeing. The replication licensing machinery is crucial for replication precision as it ensures that replication takes place once per cell cycle. Thus, the expression status of the components comprising the replication licensing apparatus is tightly regulated to avoid re-replication; a form of replication stress that leads to genomic instability, a hallmark of cancer. In the present review we discuss the mechanistic basis of replication licensing deregulation, which leads to systemic effects, exemplified by its role in carcinogenesis and a variety of genetic syndromes. In addition, new insights demonstrate that above a particular threshold, the replication licensing factor Cdc6 acts as global transcriptional regulator, outlining new lines of exploration. The role of the putative replication licensing factor ChlR1/DDX11, mutated in the Warsaw Breakage Syndrome, in cancer is also considered. Finally, future perspectives focused on the potential therapeutic advantage by targeting replication licensing factors, and particularly Cdc6, are discussed.
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Affiliation(s)
- Theodoros G Petrakis
- Molecular Carcinogenesis Group, Department of Histology and Embryology, School of Medicine, University of Athens, Athens, Greece
| | - Eirini-Stavroula Komseli
- Molecular Carcinogenesis Group, Department of Histology and Embryology, School of Medicine, University of Athens, Athens, Greece
| | - Marilena Papaioannou
- Molecular Carcinogenesis Group, Department of Histology and Embryology, School of Medicine, University of Athens, Athens, Greece
| | - Kostas Vougas
- Biomedical Research Foundation of the Academy of Athens, Athens, Greece
| | | | | | - Emmanuel Mikros
- Department of Pharmaceutical Chemistry, School of Pharmacy, University of Athens, Athens, Greece
| | - Ioannis P Trougakos
- Department of Cell Biology and Biophysics, Faculty of Biology, University of Athens, Athens, Greece
| | - Dimitris Thanos
- Biomedical Research Foundation of the Academy of Athens, Athens, Greece
| | - Dana Branzei
- FIRC (Fondazione Italiana per la Ricerca sul Cancro) Institute of Molecular Oncology (IFOM), Milan, Italy
| | - Paul Townsend
- Faculty Institute of Cancer Sciences, University of Manchester, Manchester Academic Health Science Centre, Manchester, UK
| | - Vassilis G Gorgoulis
- Molecular Carcinogenesis Group, Department of Histology and Embryology, School of Medicine, University of Athens, Athens, Greece; Biomedical Research Foundation of the Academy of Athens, Athens, Greece; Faculty Institute of Cancer Sciences, University of Manchester, Manchester Academic Health Science Centre, Manchester, UK.
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Sarni D, Kerem B. The complex nature of fragile site plasticity and its importance in cancer. Curr Opin Cell Biol 2016; 40:131-136. [PMID: 27062332 DOI: 10.1016/j.ceb.2016.03.017] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Revised: 03/21/2016] [Accepted: 03/28/2016] [Indexed: 01/12/2023]
Abstract
Common fragile sites (CFSs) are chromosomal regions characterized as hotspots for breakage and chromosomal rearrangements following DNA replication stress. They are preferentially unstable in pre-cancerous lesions and during cancer development. Recently CFSs were found to be tissue- and even oncogene-induced specific, thus indicating an unforeseen complexity. Here we review recent developments in CFS research that shed new light on the molecular basis of their instability and their importance in cancer development.
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Affiliation(s)
- Dan Sarni
- Department of Genetics, The Life Sciences Institute, The Hebrew University, Jerusalem 91904, Israel
| | - Batsheva Kerem
- Department of Genetics, The Life Sciences Institute, The Hebrew University, Jerusalem 91904, Israel.
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Lan H, Chen CL, Miao Y, Yu CX, Guo WW, Xu Q, Deng XX. Fragile Sites of 'Valencia' Sweet Orange (Citrus sinensis) Chromosomes Are Related with Active 45s rDNA. PLoS One 2016; 11:e0151512. [PMID: 26977938 PMCID: PMC4792391 DOI: 10.1371/journal.pone.0151512] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Accepted: 02/29/2016] [Indexed: 12/12/2022] Open
Abstract
Citrus sinensis chromosomes present a morphological differentiation of bands after staining by the fluorochromes CMA and DAPI, but there is still little information on its chromosomal characteristics. In this study, the chromosomes in 'Valencia' C. sinensis were analyzed by fluorescence in situ hybridization (FISH) using telomere DNA and the 45S rDNA gene as probes combining CMA/DAPI staining, which showed that there were two fragile sites in sweet orange chromosomes co-localizing at distended 45S rDNA regions, one proximally locating on B-type chromosome and the other subterminally locating on D-type chromosome. While the chromosomal CMA banding and 45S rDNA FISH mapping in the doubled haploid line of 'Valencia' C. sinensis indicated six 45S rDNA regions, four were identified as fragile sites as doubled comparing its parental line, which confirmed the cytological heterozygosity and chromosomal heteromorphisms in sweet orange. Furthermore, Ag-NOR identified two distended 45S rDNA regions to be active nucleolar organizing regions (NORs) in diploid 'Valencia' C. sinensis. The occurrence of quadrivalent in meiosis of pollen mother cells (PMCs) in 'Valencia' sweet orange further confirmed it was a chromosomal reciprocal translocation line. We speculated this chromosome translocation was probably related to fragile sites. Our data provide insights into the chromosomal characteristics of the fragile sites in 'Valencia' sweet orange and are expected to facilitate the further investigation of the possible functions of fragile sites.
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Affiliation(s)
- Hong Lan
- Key Laboratory of Horticultural Plant Biology (Ministry of Education), Huazhong Agricultural University, Wuhan, 430070, China
| | - Chun-Li Chen
- College of Life Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China
| | - Yin Miao
- College of Life Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China
| | - Chang-Xiu Yu
- College of Life Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China
| | - Wen-Wu Guo
- Key Laboratory of Horticultural Plant Biology (Ministry of Education), Huazhong Agricultural University, Wuhan, 430070, China
| | - Qiang Xu
- Key Laboratory of Horticultural Plant Biology (Ministry of Education), Huazhong Agricultural University, Wuhan, 430070, China
| | - Xiu-Xin Deng
- Key Laboratory of Horticultural Plant Biology (Ministry of Education), Huazhong Agricultural University, Wuhan, 430070, China
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Tokunaga A, Anai H, Hanada K. Mechanisms of gene targeting in higher eukaryotes. Cell Mol Life Sci 2016; 73:523-33. [PMID: 26507245 PMCID: PMC11108335 DOI: 10.1007/s00018-015-2073-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Revised: 10/14/2015] [Accepted: 10/14/2015] [Indexed: 10/22/2022]
Abstract
Targeted genome modifications using techniques that alter the genomic information of interest have contributed to multiple studies in both basic and applied biology. Traditionally, in gene targeting, the target-site integration of a targeting vector by homologous recombination is used. However, this strategy has several technical problems. The first problem is the extremely low frequency of gene targeting, which makes obtaining recombinant clones an extremely labor intensive task. The second issue is the limited number of biomaterials to which gene targeting can be applied. Traditional gene targeting hardly occurs in most of the human adherent cell lines. However, a new approach using designer nucleases that can introduce site-specific double-strand breaks in genomic DNAs has increased the efficiency of gene targeting. This new method has also expanded the number of biomaterials to which gene targeting could be applied. Here, we summarize various strategies for target gene modification, including a comparison of traditional gene targeting with designer nucleases.
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Affiliation(s)
- Akinori Tokunaga
- The Tokunaga Laboratory, Faculty of Medicine, Oita University, 1-1 Idaigaoka, Hasama-machi, Yufu, Oita, 879-5593, Japan
- Section of Physiology, Department of Integrative Aging Neuroscience, National Center for Geriatrics and Gerontology (NCGG), 7-430, Morioka-cho, Obu, Aichi, 474-8511, Japan
| | - Hirofumi Anai
- Clinical Engineering Research Center, Faculty of Medicine, Oita University, 1-1 Idaigaoka, Hasama-machi, Yufu, Oita, 879-5593, Japan
| | - Katsuhiro Hanada
- Clinical Engineering Research Center, Faculty of Medicine, Oita University, 1-1 Idaigaoka, Hasama-machi, Yufu, Oita, 879-5593, Japan.
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The DNA damage response and immune signaling alliance: Is it good or bad? Nature decides when and where. Pharmacol Ther 2015; 154:36-56. [PMID: 26145166 DOI: 10.1016/j.pharmthera.2015.06.011] [Citation(s) in RCA: 117] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Accepted: 06/10/2015] [Indexed: 12/15/2022]
Abstract
The characteristic feature of healthy living organisms is the preservation of homeostasis. Compelling evidence highlight that the DNA damage response and repair (DDR/R) and immune response (ImmR) signaling networks work together favoring the harmonized function of (multi)cellular organisms. DNA and RNA viruses activate the DDR/R machinery in the host cells both directly and indirectly. Activation of DDR/R in turn favors the immunogenicity of the incipient cell. Hence, stimulation of DDR/R by exogenous or endogenous insults triggers innate and adaptive ImmR. The immunogenic properties of ionizing radiation, a prototypic DDR/R inducer, serve as suitable examples of how DDR/R stimulation alerts host immunity. Thus, critical cellular danger signals stimulate defense at the systemic level and vice versa. Disruption of DDR/R-ImmR cross talk compromises (multi)cellular integrity, leading to cell-cycle-related and immune defects. The emerging DDR/R-ImmR concept opens up a new avenue of therapeutic options, recalling the Hippocrates quote "everything in excess is opposed by nature."
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Thys RG, Lehman CE, Pierce LCT, Wang YH. DNA secondary structure at chromosomal fragile sites in human disease. Curr Genomics 2015; 16:60-70. [PMID: 25937814 PMCID: PMC4412965 DOI: 10.2174/1389202916666150114223205] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Revised: 01/09/2015] [Accepted: 01/14/2015] [Indexed: 11/22/2022] Open
Abstract
DNA has the ability to form a variety of secondary structures that can interfere with normal cellular processes, and many of these structures have been associated with neurological diseases and cancer. Secondary structure-forming sequences are often found at chromosomal fragile sites, which are hotspots for sister chromatid exchange, chromosomal translocations, and deletions. Structures formed at fragile sites can lead to instability by disrupting normal cellular processes such as DNA replication and transcription. The instability caused by disruption of replication and transcription can lead to DNA breakage, resulting in gene rearrangements and deletions that cause disease. In this review, we discuss the role of DNA secondary structure at fragile sites in human disease.
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Affiliation(s)
- Ryan G Thys
- Department of Cancer Biology, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157, USA
| | - Christine E Lehman
- Department of Cancer Biology, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157, USA
| | | | - Yuh-Hwa Wang
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA
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