1
|
Mirceta M, Shum N, Schmidt MHM, Pearson CE. Fragile sites, chromosomal lesions, tandem repeats, and disease. Front Genet 2022; 13:985975. [PMID: 36468036 PMCID: PMC9714581 DOI: 10.3389/fgene.2022.985975] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Accepted: 09/02/2022] [Indexed: 09/16/2023] Open
Abstract
Expanded tandem repeat DNAs are associated with various unusual chromosomal lesions, despiralizations, multi-branched inter-chromosomal associations, and fragile sites. Fragile sites cytogenetically manifest as localized gaps or discontinuities in chromosome structure and are an important genetic, biological, and health-related phenomena. Common fragile sites (∼230), present in most individuals, are induced by aphidicolin and can be associated with cancer; of the 27 molecularly-mapped common sites, none are associated with a particular DNA sequence motif. Rare fragile sites ( ≳ 40 known), ≤ 5% of the population (may be as few as a single individual), can be associated with neurodevelopmental disease. All 10 molecularly-mapped folate-sensitive fragile sites, the largest category of rare fragile sites, are caused by gene-specific CGG/CCG tandem repeat expansions that are aberrantly CpG methylated and include FRAXA, FRAXE, FRAXF, FRA2A, FRA7A, FRA10A, FRA11A, FRA11B, FRA12A, and FRA16A. The minisatellite-associated rare fragile sites, FRA10B, FRA16B, can be induced by AT-rich DNA-ligands or nucleotide analogs. Despiralized lesions and multi-branched inter-chromosomal associations at the heterochromatic satellite repeats of chromosomes 1, 9, 16 are inducible by de-methylating agents like 5-azadeoxycytidine and can spontaneously arise in patients with ICF syndrome (Immunodeficiency Centromeric instability and Facial anomalies) with mutations in genes regulating DNA methylation. ICF individuals have hypomethylated satellites I-III, alpha-satellites, and subtelomeric repeats. Ribosomal repeats and subtelomeric D4Z4 megasatellites/macrosatellites, are associated with chromosome location, fragility, and disease. Telomere repeats can also assume fragile sites. Dietary deficiencies of folate or vitamin B12, or drug insults are associated with megaloblastic and/or pernicious anemia, that display chromosomes with fragile sites. The recent discovery of many new tandem repeat expansion loci, with varied repeat motifs, where motif lengths can range from mono-nucleotides to megabase units, could be the molecular cause of new fragile sites, or other chromosomal lesions. This review focuses on repeat-associated fragility, covering their induction, cytogenetics, epigenetics, cell type specificity, genetic instability (repeat instability, micronuclei, deletions/rearrangements, and sister chromatid exchange), unusual heritability, disease association, and penetrance. Understanding tandem repeat-associated chromosomal fragile sites provides insight to chromosome structure, genome packaging, genetic instability, and disease.
Collapse
Affiliation(s)
- Mila Mirceta
- Program of Genetics and Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, ON, Canada
- Program of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Natalie Shum
- Program of Genetics and Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, ON, Canada
- Program of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Monika H. M. Schmidt
- Program of Genetics and Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, ON, Canada
- Program of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Christopher E. Pearson
- Program of Genetics and Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, ON, Canada
- Program of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| |
Collapse
|
2
|
Ji F, Zhu X, Liao H, Ouyang L, Huang Y, Syeda MZ, Ying S. New Era of Mapping and Understanding Common Fragile Sites: An Updated Review on Origin of Chromosome Fragility. Front Genet 2022; 13:906957. [PMID: 35669181 PMCID: PMC9164283 DOI: 10.3389/fgene.2022.906957] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Accepted: 04/25/2022] [Indexed: 11/13/2022] Open
Abstract
Common fragile sites (CFSs) are specific genomic loci prone to forming gaps or breakages upon replication perturbation, which correlate well with chromosomal rearrangement and copy number variation. CFSs have been actively studied due to their important pathophysiological relevance in different diseases such as cancer and neurological disorders. The genetic locations and sequences of CFSs are crucial to understanding the origin of such unstable sites, which require reliable mapping and characterizing approaches. In this review, we will inspect the evolving techniques for CFSs mapping, especially genome-wide mapping and sequencing of CFSs based on current knowledge of CFSs. We will also revisit the well-established hypotheses on the origin of CFSs fragility, incorporating novel findings from the comprehensive analysis of finely mapped CFSs regarding their locations, sequences, and replication/transcription, etc. This review will present the most up-to-date picture of CFSs and, potentially, a new framework for future research of CFSs.
Collapse
Affiliation(s)
- Fang Ji
- International Institutes of Medicine, The Fourth Affiliated Hospital of Zhejiang University School of Medicine, Yiwu, China.,Department of Pharmacology and Department of Respiratory and Critical Care Medicine of the Second Affiliated Hospital, Key Laboratory of Respiratory Disease of Zhejiang Province, Zhejiang University School of Medicine, Hangzhou, China
| | - Xinli Zhu
- Department of Respiratory and Critical Care Medicine of the Second Affiliated Hospital, Key Laboratory of Respiratory Disease of Zhejiang Province, Zhejiang University School of Medicine, Hangzhou, China
| | - Hongwei Liao
- International Institutes of Medicine, The Fourth Affiliated Hospital of Zhejiang University School of Medicine, Yiwu, China.,Department of Pharmacology and Department of Respiratory and Critical Care Medicine of the Second Affiliated Hospital, Key Laboratory of Respiratory Disease of Zhejiang Province, Zhejiang University School of Medicine, Hangzhou, China
| | - Liujian Ouyang
- Department of Pharmacology and Department of Respiratory and Critical Care Medicine of the Second Affiliated Hospital, Key Laboratory of Respiratory Disease of Zhejiang Province, Zhejiang University School of Medicine, Hangzhou, China
| | - Yingfei Huang
- Department of Pharmacology and Department of Respiratory and Critical Care Medicine of the Second Affiliated Hospital, Key Laboratory of Respiratory Disease of Zhejiang Province, Zhejiang University School of Medicine, Hangzhou, China
| | - Madiha Zahra Syeda
- Department of Pharmacology and Department of Respiratory and Critical Care Medicine of the Second Affiliated Hospital, Key Laboratory of Respiratory Disease of Zhejiang Province, Zhejiang University School of Medicine, Hangzhou, China
| | - Songmin Ying
- International Institutes of Medicine, The Fourth Affiliated Hospital of Zhejiang University School of Medicine, Yiwu, China.,Department of Pharmacology and Department of Respiratory and Critical Care Medicine of the Second Affiliated Hospital, Key Laboratory of Respiratory Disease of Zhejiang Province, Zhejiang University School of Medicine, Hangzhou, China
| |
Collapse
|
3
|
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.
Collapse
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,
| |
Collapse
|
4
|
Ji F, Liao H, Pan S, Ouyang L, Jia F, Fu Z, Zhang F, Geng X, Wang X, Li T, Liu S, Syeda MZ, Chen H, Li W, Chen Z, Shen H, Ying S. Genome-wide high-resolution mapping of mitotic DNA synthesis sites and common fragile sites by direct sequencing. Cell Res 2020; 30:1009-1023. [PMID: 32561861 DOI: 10.1038/s41422-020-0357-y] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Accepted: 05/31/2020] [Indexed: 01/13/2023] Open
Abstract
Common fragile sites (CFSs) are genomic loci prone to the formation of breaks or gaps on metaphase chromosomes. They are hotspots for chromosome rearrangements and structural variations, which have been extensively implicated in carcinogenesis, aging, and other pathological processes. Although many CFSs were identified decades ago, a consensus is still lacking for why they are particularly unstable and sensitive to replication perturbations. This is in part due to the lack of high-resolution mapping data for the vast majority of the CFSs, which has hindered mechanistic interrogations. Here, we seek to map human CFSs with high resolution on a genome-wide scale by sequencing the sites of mitotic DNA synthesis (MiDASeq) that are specific for CFSs. We generated a nucleotide-resolution atlas of MiDAS sites (MDSs) that covered most of the known CFSs, and comprehensively analyzed their sequence characteristics and genomic features. Our data on MDSs tallied well with long-standing hypotheses to explain CFS fragility while highlighting the contributions of late replication timing and large transcription units. Notably, the MDSs also encompassed most of the recurrent double-strand break clusters previously identified in mouse neural stem/progenitor cells, thus bridging evolutionarily conserved break points across species. Moreover, MiDAseq provides an important resource that can stimulate future research on CFSs to further unravel the mechanisms and biological relevance underlying these labile genomic regions.
Collapse
Affiliation(s)
- Fang Ji
- Department of Pharmacology & Department of Respiratory and Critical Care Medicine of the Second Affiliated Hospital, Zhejiang University School of Medicine, Key Laboratory of Respiratory Disease of Zhejiang Province, Hangzhou, Zhejiang, 310009, China
| | - Hongwei Liao
- Department of Pharmacology & Department of Respiratory and Critical Care Medicine of the Second Affiliated Hospital, Zhejiang University School of Medicine, Key Laboratory of Respiratory Disease of Zhejiang Province, Hangzhou, Zhejiang, 310009, China
| | - Sheng Pan
- Department of Pharmacology & Department of Respiratory and Critical Care Medicine of the Second Affiliated Hospital, Zhejiang University School of Medicine, Key Laboratory of Respiratory Disease of Zhejiang Province, Hangzhou, Zhejiang, 310009, China.,Chu Kochen Honors College of Zhejiang University, Hangzhou, Zhejiang, China
| | - Liujian Ouyang
- Department of Pharmacology & Department of Respiratory and Critical Care Medicine of the Second Affiliated Hospital, Zhejiang University School of Medicine, Key Laboratory of Respiratory Disease of Zhejiang Province, Hangzhou, Zhejiang, 310009, China.,Chu Kochen Honors College of Zhejiang University, Hangzhou, Zhejiang, China
| | - Fang Jia
- Department of Pharmacology & Department of Respiratory and Critical Care Medicine of the Second Affiliated Hospital, Zhejiang University School of Medicine, Key Laboratory of Respiratory Disease of Zhejiang Province, Hangzhou, Zhejiang, 310009, China.,Chu Kochen Honors College of Zhejiang University, Hangzhou, Zhejiang, China
| | - Zaiyang Fu
- Department of Pharmacology & Department of Respiratory and Critical Care Medicine of the Second Affiliated Hospital, Zhejiang University School of Medicine, Key Laboratory of Respiratory Disease of Zhejiang Province, Hangzhou, Zhejiang, 310009, China.,Chu Kochen Honors College of Zhejiang University, Hangzhou, Zhejiang, China
| | - Fengjiao Zhang
- Department of Pharmacology & Department of Respiratory and Critical Care Medicine of the Second Affiliated Hospital, Zhejiang University School of Medicine, Key Laboratory of Respiratory Disease of Zhejiang Province, Hangzhou, Zhejiang, 310009, China
| | - Xinwei Geng
- Department of Pharmacology & Department of Respiratory and Critical Care Medicine of the Second Affiliated Hospital, Zhejiang University School of Medicine, Key Laboratory of Respiratory Disease of Zhejiang Province, Hangzhou, Zhejiang, 310009, China
| | - Xinming Wang
- School of Life Sciences, Peking University, Beijing, 100871, China
| | - Tingting Li
- State Key Laboratory of Proteomics, National Center of Biomedical Analysis, Institute of Basic Medical Sciences, Beijing, 100850, China
| | - Shuangying Liu
- Department of Pharmacology & Department of Respiratory and Critical Care Medicine of the Second Affiliated Hospital, Zhejiang University School of Medicine, Key Laboratory of Respiratory Disease of Zhejiang Province, Hangzhou, Zhejiang, 310009, China.,Chu Kochen Honors College of Zhejiang University, Hangzhou, Zhejiang, China
| | - Madiha Zahra Syeda
- Department of Pharmacology & Department of Respiratory and Critical Care Medicine of the Second Affiliated Hospital, Zhejiang University School of Medicine, Key Laboratory of Respiratory Disease of Zhejiang Province, Hangzhou, Zhejiang, 310009, China
| | - Haixia Chen
- Key Laboratory of Respiratory Disease of Zhejiang Province, Department of Respiratory and Critical Care Medicine, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310009, China
| | - Wen Li
- Key Laboratory of Respiratory Disease of Zhejiang Province, Department of Respiratory and Critical Care Medicine, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310009, China
| | - Zhihua Chen
- Key Laboratory of Respiratory Disease of Zhejiang Province, Department of Respiratory and Critical Care Medicine, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310009, China
| | - Huahao Shen
- Key Laboratory of Respiratory Disease of Zhejiang Province, Department of Respiratory and Critical Care Medicine, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310009, China. .,State Key Laboratory of Respiratory Diseases, Guangzhou, Guangdong, 510120, China.
| | - Songmin Ying
- Department of Pharmacology & Department of Respiratory and Critical Care Medicine of the Second Affiliated Hospital, Zhejiang University School of Medicine, Key Laboratory of Respiratory Disease of Zhejiang Province, Hangzhou, Zhejiang, 310009, China.
| |
Collapse
|
5
|
Zhao PA, Sasaki T, Gilbert DM. High-resolution Repli-Seq defines the temporal choreography of initiation, elongation and termination of replication in mammalian cells. Genome Biol 2020; 21:76. [PMID: 32209126 PMCID: PMC7092589 DOI: 10.1186/s13059-020-01983-8] [Citation(s) in RCA: 68] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Accepted: 03/04/2020] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND DNA replication in mammalian cells occurs in a defined temporal order during S phase, known as the replication timing (RT) programme. Replication timing is developmentally regulated and correlated with chromatin conformation and local transcriptional potential. Here, we present RT profiles of unprecedented temporal resolution in two human embryonic stem cell lines, human colon carcinoma line HCT116, and mouse embryonic stem cells and their neural progenitor derivatives. RESULTS Fine temporal windows revealed a remarkable degree of cell-to-cell conservation in RT, particularly at the very beginning and ends of S phase, and identified 5 temporal patterns of replication in all cell types, consistent with varying degrees of initiation efficiency. Zones of replication initiation (IZs) were detected throughout S phase and interacted in 3D space preferentially with other IZs of similar firing time. Temporal transition regions were resolved into segments of uni-directional replication punctuated at specific sites by small, inefficient IZs. Sites of convergent replication were divided into sites of termination or large constant timing regions consisting of many synchronous IZs in tandem. Developmental transitions in RT occured mainly by activating or inactivating individual IZs or occasionally by altering IZ firing time, demonstrating that IZs, rather than individual origins, are the units of developmental regulation. Finally, haplotype phasing revealed numerous regions of allele-specific and allele-independent asynchronous replication. Allele-independent asynchronous replication was correlated with the presence of previously mapped common fragile sites. CONCLUSIONS Altogether, these data provide a detailed temporal choreography of DNA replication in mammalian cells.
Collapse
Affiliation(s)
- Peiyao A Zhao
- Department of Biological Science, Florida State University, 319 Stadium Drive, Tallahassee, FL, 32306, USA
| | - Takayo Sasaki
- Department of Biological Science, Florida State University, 319 Stadium Drive, Tallahassee, FL, 32306, USA
| | - David M Gilbert
- Department of Biological Science, Florida State University, 319 Stadium Drive, Tallahassee, FL, 32306, USA.
| |
Collapse
|
6
|
Impaired Replication Timing Promotes Tissue-Specific Expression of Common Fragile Sites. Genes (Basel) 2020; 11:genes11030326. [PMID: 32204553 PMCID: PMC7140878 DOI: 10.3390/genes11030326] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Revised: 02/27/2020] [Accepted: 03/06/2020] [Indexed: 12/24/2022] Open
Abstract
Common fragile sites (CFSs) are particularly vulnerable regions of the genome that become visible as breaks, gaps, or constrictions on metaphase chromosomes when cells are under replicative stress. Impairment in DNA replication, late replication timing, enrichment of A/T nucleotides that tend to form secondary structures, the paucity of active or inducible replication origins, the generation of R-loops, and the collision between replication and transcription machineries on particularly long genes are some of the reported characteristics of CFSs that may contribute to their tissue-specific fragility. Here, we validated the induction of two CFSs previously found in the human fetal lung fibroblast line, Medical Research Council cell strain 5 (MRC-5), in another cell line derived from the same fetal tissue, Institute for Medical Research-90 cells (IMR-90). After induction of CFSs through aphidicolin, we confirmed the expression of the CFS 1p31.1 on chromosome 1 and CFS 3q13.3 on chromosome 3 in both fetal lines. Interestingly, these sites were found to not be fragile in lymphocytes, suggesting a role for epigenetic or transcriptional programs for this tissue specificity. Both these sites contained late-replicating genes NEGR1 (neuronal growth regulator 1) at 1p31.1 and LSAMP (limbic system-associated membrane protein) at 3q13.3, which are much longer, 0.880 and 1.4 Mb, respectively, than the average gene length. Given the established connection between long genes and CFS, we compiled information from the literature on all previously identified CFSs expressed in fibroblasts and lymphocytes in response to aphidicolin, including the size of the genes contained in each fragile region. Our comprehensive analysis confirmed that the genes found within CFSs are longer than the average human gene; interestingly, the two longest genes in the human genome are found within CFSs: Contactin Associated Protein 2 gene (CNTNAP2) in a lymphocytes’ CFS, and Duchenne muscular dystrophy gene (DMD) in a CFS expressed in both lymphocytes and fibroblasts. This indicates that the presence of very long genes is a unifying feature of all CFSs. We also obtained replication profiles of the 1p31.1 and 3q13.3 sites under both perturbed and unperturbed conditions using a combination of fluorescent in situ hybridization (FISH) and immunofluorescence against bromodeoxyuridine (BrdU) on interphase nuclei. Our analysis of the replication dynamics of these CFSs showed that, compared to lymphocytes where these regions are non-fragile, fibroblasts display incomplete replication of the fragile alleles, even in the absence of exogenous replication stress. Our data point to the existence of intrinsic features, in addition to the presence of long genes, which affect DNA replication of the CFSs in fibroblasts, thus promoting chromosomal instability in a tissue-specific manner.
Collapse
|
7
|
Abstract
Common fragile sites (CFSs) are large chromosomal regions that exhibit breakage on metaphase chromosomes upon replication stress. They become preferentially unstable at the early stage of cancer development and are hotspots for chromosomal rearrangements in cancers. Increasing evidence has highlighted the complexity underlying the instability of CFSs, and a combination of multiple mechanisms is believed to cause CFS fragility. We will review recent advancements in our understanding of the molecular mechanisms underlying the maintenance of CFS stability and the relevance of CFSs to cancer-associated genome instability. We will emphasize the contribution of the structure-prone AT-rich sequences to CFS instability, which is in line with the recent genome-wide study showing that structure-forming repeat sequences are principal sites of replication stress.
Collapse
Affiliation(s)
- Shibo Li
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, San Diego, CA 92037 USA
| | - Xiaohua Wu
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, San Diego, CA 92037 USA
| |
Collapse
|
8
|
From R-Loops to G-Quadruplexes: Emerging New Threats for the Replication Fork. Int J Mol Sci 2020; 21:ijms21041506. [PMID: 32098397 PMCID: PMC7073102 DOI: 10.3390/ijms21041506] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 02/14/2020] [Accepted: 02/20/2020] [Indexed: 12/12/2022] Open
Abstract
Replicating the entire genome is one of the most complex tasks for all organisms. Research carried out in the last few years has provided us with a clearer picture on how cells preserve genomic information from the numerous insults that may endanger its stability. Different DNA repair pathways, coping with exogenous or endogenous threat, have been dissected at the molecular level. More recently, there has been an increasing interest towards intrinsic obstacles to genome replication, paving the way to a novel view on genomic stability. Indeed, in some cases, the movement of the replication fork can be hindered by the presence of stable DNA: RNA hybrids (R-loops), the folding of G-rich sequences into G-quadruplex structures (G4s) or repetitive elements present at Common Fragile Sites (CFS). Although differing in their nature and in the way they affect the replication fork, all of these obstacles are a source of replication stress. Replication stress is one of the main hallmarks of cancer and its prevention is becoming increasingly important as a target for future chemotherapeutics. Here we will try to summarize how these three obstacles are generated and how the cells handle replication stress upon their encounter. Finally, we will consider their role in cancer and their exploitation in current chemotherapeutic approaches.
Collapse
|
9
|
Irony-Tur Sinai M, Kerem B. Genomic instability in fragile sites-still adding the pieces. Genes Chromosomes Cancer 2018; 58:295-304. [PMID: 30525255 DOI: 10.1002/gcc.22715] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2018] [Revised: 11/28/2018] [Accepted: 11/29/2018] [Indexed: 12/19/2022] Open
Abstract
Common fragile sites (CFSs) are specific genomic regions in normal chromosomes that exhibit genomic instability under DNA replication stress. As replication stress is an early feature of cancer development, CFSs are involved in the signature of genomic instability found in malignant tumors. The landscape of CFSs is tissue-specific and differs under different replication stress inducers. Nevertheless, the features underlying CFS sensitivity to replication stress are shared. Here, we review the events generating replication stress and discuss the unique characteristics of CFS regions and the cellular responses aimed to stabilizing these regions.
Collapse
Affiliation(s)
- Michal Irony-Tur Sinai
- Department of Genetics, The Life Sciences Institute, The Hebrew University, Jerusalem, Israel
| | - Batsheva Kerem
- Department of Genetics, The Life Sciences Institute, The Hebrew University, Jerusalem, Israel
| |
Collapse
|
10
|
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.
Collapse
Affiliation(s)
- Elisa Palumbo
- Department of Molecular Medicine, University of Padova, Padova, Italy
| | - Antonella Russo
- Department of Molecular Medicine, University of Padova, Padova, Italy
| |
Collapse
|
11
|
Bertoletti F, Cea V, Liang CC, Lanati T, Maffia A, Avarello MDM, Cipolla L, Lehmann AR, Cohn MA, Sabbioneda S. Phosphorylation regulates human polη stability and damage bypass throughout the cell cycle. Nucleic Acids Res 2017; 45:9441-9454. [PMID: 28934491 PMCID: PMC5766190 DOI: 10.1093/nar/gkx619] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Accepted: 07/06/2017] [Indexed: 01/22/2023] Open
Abstract
DNA translesion synthesis (TLS) is a crucial damage tolerance pathway that oversees the completion of DNA replication in the presence of DNA damage. TLS polymerases are capable of bypassing a distorted template but they are generally considered inaccurate and they need to be tightly regulated. We have previously shown that polη is phosphorylated on Serine 601 after DNA damage and we have demonstrated that this modification is important for efficient damage bypass. Here we report that polη is also phosphorylated by CDK2, in the absence of damage, in a cell cycle-dependent manner and we identify serine 687 as an important residue targeted by the kinase. We discover that phosphorylation on serine 687 regulates the stability of the polymerase during the cell cycle, allowing it to accumulate in late S and G2 when productive TLS is critical for cell survival. Furthermore, we show that alongside the phosphorylation of S601, the phosphorylation of S687 and S510, S512 and/or S514 are important for damage bypass and cell survival after UV irradiation. Taken together our results provide new insights into how cells can, at different times, modulate DNA TLS for improved cell survival.
Collapse
Affiliation(s)
| | - Valentina Cea
- Istituto di Genetica Molecolare-CNR, 27100, Pavia, Italy
| | - Chih-Chao Liang
- Department of Biochemistry, University of Oxford, OX1 3QU, Oxford, UK
| | - Taiba Lanati
- Istituto di Genetica Molecolare-CNR, 27100, Pavia, Italy
| | - Antonio Maffia
- Istituto di Genetica Molecolare-CNR, 27100, Pavia, Italy.,Dipartimento di Biologia e Biotecnologie 'Lazzaro Spallanzani', Universita' degli Studi di Pavia, 27100, Pavia, Italy
| | | | - Lina Cipolla
- Istituto di Genetica Molecolare-CNR, 27100, Pavia, Italy
| | - Alan R Lehmann
- Genome Damage and Stability Centre, University of Sussex, BN1 9RQ, Brighton, UK
| | - Martin A Cohn
- Department of Biochemistry, University of Oxford, OX1 3QU, Oxford, UK
| | | |
Collapse
|
12
|
Irony-Tur Sinai M, Kerem B. DNA replication stress drives fragile site instability. Mutat Res 2017; 808:56-61. [PMID: 29074228 DOI: 10.1016/j.mrfmmm.2017.10.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Revised: 09/26/2017] [Accepted: 10/12/2017] [Indexed: 12/21/2022]
Abstract
DNA replication stress is one of the early drivers enabling the ongoing acquisition of genetic changes arising during tumorigenesis. As such, it is a feature of most pre-malignant and malignant cells. In this review article, we focus on the early events initiating DNA replication stress and the preferential sensitivity of common fragile sites (CFSs) to this stress. CFSs are specific genomic regions within the normal chromosomal structure, which appear as gaps and breaks in the metaphase chromosomes of cells grown under mild replication stress conditions. The main characteristics predisposing CFSs to instability include late replication timing, delayed replication completion, failure to activate additional origins, origin paucity along large genomic regions, collision between replication and transcription complexes along large genes, and the presence of AT-dinucleotide rich sequences. The contribution of these features to instability at CFSs during early cancer development is discussed.
Collapse
Affiliation(s)
- Michal Irony-Tur Sinai
- 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.
| |
Collapse
|
13
|
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.
Collapse
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.
| |
Collapse
|
14
|
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.
Collapse
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
| |
Collapse
|
15
|
Ozeri-Galai E, Tur-Sinai M, Bester AC, Kerem B. Interplay between genetic and epigenetic factors governs common fragile site instability in cancer. Cell Mol Life Sci 2014; 71:4495-506. [PMID: 25297918 PMCID: PMC11113459 DOI: 10.1007/s00018-014-1719-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Accepted: 08/28/2014] [Indexed: 11/28/2022]
Abstract
Common fragile sites (CFSs) are regions within the normal chromosomal structure that were characterized as hotspots for genomic instability in cancer almost 30 years ago. In recent years, many efforts have been made to understand the basis of CFS fragility and their involvement in the genomic signature of instability found in malignant tumors. CFSs are among the first regions to undergo genomic instability during cancer development because of their intrinsic sensitivity to replication stress conditions, which result from oncogene expression. The preferred sensitivity of CFSs to replication stress stems from various mechanisms including: replication fork arrest at AT-rich repeats, origin paucity along large genomic regions, failure in activation of dormant origins, late replication timing, collision between replication and transcription along large genes, all leading to incomplete replication of the CFS region and resulting in chromosomal instability. Here we review shared and unique characteristics of CFSs, their underlying causes and implications, particularly for the development of cancer.
Collapse
Affiliation(s)
- Efrat Ozeri-Galai
- Department of Genetics, The Life Sciences Institute, The Hebrew University, Edmond J. Safra Campus, 91904 Jerusalem, Israel
| | - Michal Tur-Sinai
- Department of Genetics, The Life Sciences Institute, The Hebrew University, Edmond J. Safra Campus, 91904 Jerusalem, Israel
| | - Assaf C. Bester
- Department of Genetics, The Life Sciences Institute, The Hebrew University, Edmond J. Safra Campus, 91904 Jerusalem, Israel
| | - Batsheva Kerem
- Department of Genetics, The Life Sciences Institute, The Hebrew University, Edmond J. Safra Campus, 91904 Jerusalem, Israel
| |
Collapse
|
16
|
Dillon LW, Pierce LCT, Lehman CE, Nikiforov YE, Wang YH. DNA topoisomerases participate in fragility of the oncogene RET. PLoS One 2013; 8:e75741. [PMID: 24040417 PMCID: PMC3770543 DOI: 10.1371/journal.pone.0075741] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Accepted: 08/19/2013] [Indexed: 11/19/2022] Open
Abstract
Fragile site breakage was previously shown to result in rearrangement of the RET oncogene, resembling the rearrangements found in thyroid cancer. Common fragile sites are specific regions of the genome with a high susceptibility to DNA breakage under conditions that partially inhibit DNA replication, and often coincide with genes deleted, amplified, or rearranged in cancer. While a substantial amount of work has been performed investigating DNA repair and cell cycle checkpoint proteins vital for maintaining stability at fragile sites, little is known about the initial events leading to DNA breakage at these sites. The purpose of this study was to investigate these initial events through the detection of aphidicolin (APH)-induced DNA breakage within the RET oncogene, in which 144 APH-induced DNA breakpoints were mapped on the nucleotide level in human thyroid cells within intron 11 of RET, the breakpoint cluster region found in patients. These breakpoints were located at or near DNA topoisomerase I and/or II predicted cleavage sites, as well as at DNA secondary structural features recognized and preferentially cleaved by DNA topoisomerases I and II. Co-treatment of thyroid cells with APH and the topoisomerase catalytic inhibitors, betulinic acid and merbarone, significantly decreased APH-induced fragile site breakage within RET intron 11 and within the common fragile site FRA3B. These data demonstrate that DNA topoisomerases I and II are involved in initiating APH-induced common fragile site breakage at RET, and may engage the recognition of DNA secondary structures formed during perturbed DNA replication.
Collapse
Affiliation(s)
- Laura W. Dillon
- Department of Biochemistry, Wake Forest School of Medicine, Winston-Salem, North Carolina, United States of America
| | - Levi C. T. Pierce
- Department of Chemistry and Biochemistry, University of California-San Diego, La Jolla, California, United States of America
| | - Christine E. Lehman
- Department of Cancer Biology, Wake Forest School of Medicine, Winston-Salem, North Carolina, United States of America
| | - Yuri E. Nikiforov
- Department of Pathology and Laboratory Medicine, University of Pittsburgh, Pennsylvania, United States of America
| | - Yuh-Hwa Wang
- Department of Biochemistry, Wake Forest School of Medicine, Winston-Salem, North Carolina, United States of America
- * E-mail:
| |
Collapse
|
17
|
Genome instability at common fragile sites: searching for the cause of their instability. BIOMED RESEARCH INTERNATIONAL 2013; 2013:730714. [PMID: 24083238 PMCID: PMC3780545 DOI: 10.1155/2013/730714] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/27/2013] [Accepted: 08/07/2013] [Indexed: 12/24/2022]
Abstract
Common fragile sites (CFS) are heritable nonrandomly distributed loci on human chromosomes that exhibit an increased frequency of chromosomal breakage under conditions of replication stress. They are considered the preferential targets for high genomic instability from the earliest stages of human cancer development, and increased chromosome instability at these loci has been observed following replication stress in a subset of human genetic diseases. Despite their biological and medical relevance, the molecular basis of CFS fragility in vivo has not been fully elucidated. At present, different models have been proposed to explain how instability at CFS arises and multiple factors seem to contribute to their instability. However, all these models involve DNA replication and suggest that replication fork stalling along CFS during DNA synthesis is a very frequent event. Consistent with this, the maintenance of CFS stability relies on the ATR-dependent checkpoint, together with a number of proteins promoting the recovery of stalled replication forks. In this review, we discuss mainly the possible causes that threaten the integrity of CFS in the light of new findings, paying particular attention to the role of the S-phase checkpoint.
Collapse
|
18
|
Abstract
Certain chromosomal regions called common fragile sites are prone to difficulty during replication. Many tumors have been shown to contain alterations at fragile sites. Several models have been proposed to explain why these sites are unstable. Here we describe work to investigate models of fragile site instability using a yeast artificial chromosome carrying human DNA from a common fragile site region. In addition, we describe a yeast system to investigate whether repair of breaks at a naturally occurring fragile site in yeast, FS2, involves mitotic recombination between homologous chromosomes, leading to loss of heterozygosity (LOH). Our initial evidence is that repair of yeast fragile site breaks does lead to LOH, suggesting that human fragile site breaks may similarly contribute to LOH in cancer. This work is focused on gaining understanding that may enable us to predict and prevent the situations and environments that promote genetic changes that contribute to tumor progression.
Collapse
Affiliation(s)
- Anne M Casper
- Department of Biology, Eastern Michigan University, Ypsilanti, Michigan, USA
| | | | | |
Collapse
|
19
|
Bosco N, de Lange T. A TRF1-controlled common fragile site containing interstitial telomeric sequences. Chromosoma 2012; 121:465-74. [PMID: 22790221 PMCID: PMC3590843 DOI: 10.1007/s00412-012-0377-6] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2012] [Revised: 06/11/2012] [Accepted: 06/12/2012] [Indexed: 10/28/2022]
Abstract
Mouse telomeres have been suggested to resemble common fragile sites (CFS), showing disrupted TTAGGG fluorescent in situ hybridization signals after aphidicolin treatment. This "fragile" telomere phenotype is induced by deletion of TRF1, a shelterin protein that binds telomeric DNA and promotes efficient replication of the telomeric ds[TTAGGG]n tracts. Here we show that the chromosome-internal TTAGGG repeats present at human chromosome 2q14 form an aphidicolin-induced CFS. TRF1 binds to and stabilizes CFS 2q14 but does not affect other CFS, establishing 2q14 as the first CFS controlled by a sequence-specific DNA binding protein. The data show that telomeric DNA is inherently fragile regardless of its genomic position and imply that CFS can be caused by a specific DNA sequence.
Collapse
Affiliation(s)
- Nazario Bosco
- Laboratory for Cell Biology and Genetics, The Rockefeller University, Box 159, 1230 York Avenue, New York, NY 10065, USA
| | - Titia de Lange
- Laboratory for Cell Biology and Genetics, The Rockefeller University, Box 159, 1230 York Avenue, New York, NY 10065, USA
| |
Collapse
|
20
|
Common fragile sites: genomic hotspots of DNA damage and carcinogenesis. Int J Mol Sci 2012; 13:11974-11999. [PMID: 23109895 PMCID: PMC3472787 DOI: 10.3390/ijms130911974] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2012] [Revised: 08/09/2012] [Accepted: 09/05/2012] [Indexed: 01/08/2023] Open
Abstract
Genomic instability, a hallmark of cancer, occurs preferentially at specific genomic regions known as common fragile sites (CFSs). CFSs are evolutionarily conserved and late replicating regions with AT-rich sequences, and CFS instability is correlated with cancer. In the last decade, much progress has been made toward understanding the mechanisms of chromosomal instability at CFSs. However, despite tremendous efforts, identifying a cancer-associated CFS gene (CACG) remains a challenge and little is known about the function of CACGs at most CFS loci. Recent studies of FATS (for Fragile-site Associated Tumor Suppressor), a new CACG at FRA10F, reveal an active role of this CACG in regulating DNA damage checkpoints and suppressing tumorigenesis. The identification of FATS may inspire more discoveries of other uncharacterized CACGs. Further elucidation of the biological functions and clinical significance of CACGs may be exploited for cancer biomarkers and therapeutic benefits.
Collapse
|
21
|
The role of fragile sites in sporadic papillary thyroid carcinoma. J Thyroid Res 2012; 2012:927683. [PMID: 22762011 PMCID: PMC3384961 DOI: 10.1155/2012/927683] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Accepted: 04/18/2012] [Indexed: 12/15/2022] Open
Abstract
The incidence of thyroid cancer is increasing, especially papillary thyroid carcinoma (PTC), making it currently the fastest-growing cancer among women. Reasons for this increase remain unclear, but several risk factors including radiation exposure and improved detection techniques have been suggested. Recently, the induction of chromosomal fragile site breakage was found to result in the formation of RET/PTC1 rearrangements, a common cause of PTC. Chromosomal fragile sites are regions of the genome with a high susceptibility to forming DNA breaks and are often associated with cancer. Exposure to a variety of external agents can induce fragile site breakage, which may account for some of the observed increase in PTC. This paper discusses the role of fragile site breakage in PTC development, external fragile site-inducing agents that may be potential risk factors for PTC, and how these factors are especially targeting women.
Collapse
|
22
|
Ozeri-Galai E, Bester AC, Kerem B. The complex basis underlying common fragile site instability in cancer. Trends Genet 2012; 28:295-302. [PMID: 22465609 DOI: 10.1016/j.tig.2012.02.006] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Revised: 02/23/2012] [Accepted: 02/24/2012] [Indexed: 10/28/2022]
Abstract
Common fragile sites (CFSs) were characterized almost 30 years ago as sites undergoing genomic instability in cancer. Recently, in vitro studies have found that oncogene-induced replication stress leads to CFS instability. In vivo, CFSs were found to be preferentially unstable during early stages of cancer development and to leave a unique signature of instability. It is now increasingly clear that, along the spectrum of replication features characterizing CFSs, failure of origin activation is a common feature. This and other features of CFSs, together with the replication stress characterizing early stages of cancer development, lead to incomplete replication that results in genomic instability preferentially at CFSs. Here, we review the shared and unique characteristics of CFSs, their underlying causes and their implications, particularly with respect to the development of cancer.
Collapse
Affiliation(s)
- Efrat Ozeri-Galai
- Department of Genetics, The Alexander Silberman Institute of Life Sciences, Edmond J. Safra Campus, The Hebrew University, Jerusalem 91904, Israel
| | | | | |
Collapse
|
23
|
Fungtammasan A, Walsh E, Chiaromonte F, Eckert KA, Makova KD. A genome-wide analysis of common fragile sites: what features determine chromosomal instability in the human genome? Genome Res 2012; 22:993-1005. [PMID: 22456607 PMCID: PMC3371707 DOI: 10.1101/gr.134395.111] [Citation(s) in RCA: 131] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Chromosomal common fragile sites (CFSs) are unstable genomic regions that break under replication stress and are involved in structural variation. They frequently are sites of chromosomal rearrangements in cancer and of viral integration. However, CFSs are undercharacterized at the molecular level and thus difficult to predict computationally. Newly available genome-wide profiling studies provide us with an unprecedented opportunity to associate CFSs with features of their local genomic contexts. Here, we contrasted the genomic landscape of cytogenetically defined aphidicolin-induced CFSs (aCFSs) to that of nonfragile sites, using multiple logistic regression. We also analyzed aCFS breakage frequencies as a function of their genomic landscape, using standard multiple regression. We show that local genomic features are effective predictors both of regions harboring aCFSs (explaining ∼77% of the deviance in logistic regression models) and of aCFS breakage frequencies (explaining ∼45% of the variance in standard regression models). In our optimal models (having highest explanatory power), aCFSs are predominantly located in G-negative chromosomal bands and away from centromeres, are enriched in Alu repeats, and have high DNA flexibility. In alternative models, CpG island density, transcription start site density, H3K4me1 coverage, and mononucleotide microsatellite coverage are significant predictors. Also, aCFSs have high fragility when colocated with evolutionarily conserved chromosomal breakpoints. Our models are predictive of the fragility of aCFSs mapped at a higher resolution. Importantly, the genomic features we identified here as significant predictors of fragility allow us to draw valuable inferences on the molecular mechanisms underlying aCFSs.
Collapse
Affiliation(s)
- Arkarachai Fungtammasan
- The Integrative Biosciences Graduate Program, Bioinformatics and Genomics Option, Pennsylvania State University, University Park, PA 16802, USA
| | | | | | | | | |
Collapse
|
24
|
Menicali E, Moretti S, Voce P, Romagnoli S, Avenia N, Puxeddu E. Intracellular signal transduction and modification of the tumor microenvironment induced by RET/PTCs in papillary thyroid carcinoma. Front Endocrinol (Lausanne) 2012; 3:67. [PMID: 22661970 PMCID: PMC3357465 DOI: 10.3389/fendo.2012.00067] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2012] [Accepted: 04/30/2012] [Indexed: 01/06/2023] Open
Abstract
RET gene rearrangements (RET/PTCs) represent together with BRAF point mutations the two major groups of mutations involved in papillary thyroid carcinoma (PTC) initiation and progression. In this review, we will examine the mechanisms involved in RET/PTC-induced thyroid cell transformation. In detail, we will summarize the data on the molecular mechanisms involved in RET/PTC formation and in its function as a dominant oncogene, on the activated signal transduction pathways and on the induced gene expression modifications. Moreover, we will report on the effects of RET/PTCs on the tumor microenvironment. Finally, a short review of the literature on RET/PTC prognostic significance will be presented.
Collapse
Affiliation(s)
- Elisa Menicali
- Dipartimento di Medicina, University of PerugiaPerugia, Italy
- Centro di Proteomica e Genomica della Tiroide, University of PerugiaPerugia and Terni, Italy
| | - Sonia Moretti
- Dipartimento di Medicina, University of PerugiaPerugia, Italy
- Centro di Proteomica e Genomica della Tiroide, University of PerugiaPerugia and Terni, Italy
| | - Pasquale Voce
- Dipartimento di Medicina, University of PerugiaPerugia, Italy
- Centro di Proteomica e Genomica della Tiroide, University of PerugiaPerugia and Terni, Italy
| | | | - Nicola Avenia
- Centro di Proteomica e Genomica della Tiroide, University of PerugiaPerugia and Terni, Italy
- Dipartimento di Chirurgia, University of PerugiaPerugia, Italy
| | - Efisio Puxeddu
- Dipartimento di Medicina, University of PerugiaPerugia, Italy
- Centro di Proteomica e Genomica della Tiroide, University of PerugiaPerugia and Terni, Italy
- *Correspondence: Efisio Puxeddu, Dipartimento di Medicina, Sezione MIENDO, Via Enrico dal Pozzo – Padiglione X, 06126 Perugia, Italy. e-mail:
| |
Collapse
|
25
|
Dillon LW, Burrow AA, Wang YH. DNA instability at chromosomal fragile sites in cancer. Curr Genomics 2011; 11:326-37. [PMID: 21286310 PMCID: PMC2944998 DOI: 10.2174/138920210791616699] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2010] [Revised: 05/06/2010] [Accepted: 05/18/2010] [Indexed: 01/02/2023] Open
Abstract
Human chromosomal fragile sites are specific genomic regions which exhibit gaps or breaks on metaphase chromosomes following conditions of partial replication stress. Fragile sites often coincide with genes that are frequently rearranged or deleted in human cancers, with over half of cancer-specific translocations containing breakpoints within fragile sites. But until recently, little direct evidence existed linking fragile site breakage to the formation of cancer-causing chromosomal aberrations. Studies have revealed that DNA breakage at fragile sites can induce formation of RET/PTC rearrangements, and deletions within the FHIT gene, resembling those observed in human tumors. These findings demonstrate the important role of fragile sites in cancer development, suggesting that a better understanding of the molecular basis of fragile site instability is crucial to insights in carcinogenesis. It is hypothesized that under conditions of replication stress, stable secondary structures form at fragile sites and stall replication fork progress, ultimately resulting in DNA breaks. A recent study examining an FRA16B fragment confirmed the formation of secondary structure and DNA polymerase stalling within this sequence in vitro, as well as reduced replication efficiency and increased instability in human cells. Polymerase stalling during synthesis of FRA16D has also been demonstrated. The ATR DNA damage checkpoint pathway plays a critical role in maintaining stability at fragile sites. Recent findings have confirmed binding of the ATR protein to three regions of FRA3B under conditions of mild replication stress. This review will discuss recent advances made in understanding the role and mechanism of fragile sites in cancer development.
Collapse
Affiliation(s)
- Laura W Dillon
- Department of Biochemistry, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157-1016, USA
| | | | | |
Collapse
|
26
|
Bosco N, Pelliccia F, Rocchi A. Characterization of FRA7B, a human common fragile site mapped at the 7p chromosome terminal region. ACTA ACUST UNITED AC 2010; 202:47-52. [DOI: 10.1016/j.cancergencyto.2010.06.008] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2010] [Revised: 06/10/2010] [Accepted: 06/13/2010] [Indexed: 02/07/2023]
|
27
|
Brown JD, O'Neill RJ. Chromosomes, conflict, and epigenetics: chromosomal speciation revisited. Annu Rev Genomics Hum Genet 2010; 11:291-316. [PMID: 20438362 DOI: 10.1146/annurev-genom-082509-141554] [Citation(s) in RCA: 124] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Since Darwin first noted that the process of speciation was indeed the "mystery of mysteries," scientists have tried to develop testable models for the development of reproductive incompatibilities-the first step in the formation of a new species. Early theorists proposed that chromosome rearrangements were implicated in the process of reproductive isolation; however, the chromosomal speciation model has recently been questioned. In addition, recent data from hybrid model systems indicates that simple epistatic interactions, the Dobzhansky-Muller incompatibilities, are more complex. In fact, incompatibilities are quite broad, including interactions among heterochromatin, small RNAs, and distinct, epigenetically defined genomic regions such as the centromere. In this review, we will examine both classical and current models of chromosomal speciation and describe the "evolving" theory of genetic conflict, epigenetics, and chromosomal speciation.
Collapse
Affiliation(s)
- Judith D Brown
- Department of Allied Health Sciences, University of Connecticut, Storrs, CT 06269, USA
| | | |
Collapse
|
28
|
Gandhi M, Dillon LW, Pramanik S, Nikiforov YE, Wang YH. DNA breaks at fragile sites generate oncogenic RET/PTC rearrangements in human thyroid cells. Oncogene 2010; 29:2272-80. [PMID: 20101222 PMCID: PMC2855398 DOI: 10.1038/onc.2009.502] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Human chromosomal fragile sites are regions of the genome that are prone to DNA breakage, and are classified as common or rare, depending on their frequency in the population. Common fragile sites frequently coincide with the location of genes involved in carcinogenic chromosomal translocations, suggesting their role in cancer formation. However, there has been no direct evidence linking breakage at fragile sites to the formation of a cancer-specific translocation. Here, we studied the involvement of fragile sites in the formation of RET/PTC rearrangements, which are frequently found in papillary thyroid carcinoma (PTC). These rearrangements are commonly associated with radiation exposure; however most of the tumors found in adults are not linked to radiation. In this study, we provide structural and biochemical evidence that the RET, CCDC6, and NCOA4 genes participating in two major types of RET/PTC rearrangements, are located in common fragile sites FRA10C and FRA10G, and undergo DNA breakage after exposure to fragile site-inducing chemicals. Moreover, exposure of human thyroid cells to these chemicals results in the formation of cancer-specific RET/PTC rearrangements. These results provide the direct evidence for the involvement of chromosomal fragile sites in the generation of cancer-specific rearrangements in human cells.
Collapse
Affiliation(s)
- M Gandhi
- Department of Pathology and Laboratory Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | | | | | | | | |
Collapse
|
29
|
Burrow AA, Marullo A, Holder LR, Wang YH. Secondary structure formation and DNA instability at fragile site FRA16B. Nucleic Acids Res 2010; 38:2865-77. [PMID: 20071743 PMCID: PMC2875025 DOI: 10.1093/nar/gkp1245] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Human chromosomal fragile sites are specific loci that are especially susceptible to DNA breakage following conditions of partial replication stress. They often are found in genes involved in tumorigenesis and map to over half of all known cancer-specific recurrent translocation breakpoints. While their molecular basis remains elusive, most fragile DNAs contain AT-rich flexibility islands predicted to form stable secondary structures. To understand the mechanism of fragile site instability, we examined the contribution of secondary structure formation to breakage at FRA16B. Here, we show that FRA16B forms an alternative DNA structure in vitro. During replication in human cells, FRA16B exhibited reduced replication efficiency and expansions and deletions, depending on replication orientation and distance from the origin. Furthermore, the examination of a FRA16B replication fork template demonstrated that the majority of the constructs contained DNA polymerase paused within the FRA16B sequence, and among the molecules, which completed DNA synthesis, 81% of them underwent fork reversal. These results strongly suggest that the secondary-structure-forming ability of FRA16B contributes to its fragility by stalling DNA replication, and this mechanism may be shared among other fragile DNAs.
Collapse
Affiliation(s)
- Allison A Burrow
- Department of Biochemistry, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157-1016, USA
| | | | | | | |
Collapse
|