1
|
Wan TSK, Ma ESK. Chromosome Bandings and Recognition. Methods Mol Biol 2024; 2825:137-150. [PMID: 38913307 DOI: 10.1007/978-1-0716-3946-7_7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/25/2024]
Abstract
Chromosome banding can be defined as the lengthwise variation in staining properties along a chromosome stained with a dye. Chromosome banding became more practical in the early 1970s and is an essential technique used in karyotyping to identify human chromosomes for both clinical and research purposes. Most importantly, karyotyping is now considered a mandatory investigation of all newly diagnosed leukemias. Some banding methods, such as Giemsa (G)-, reverse (R)-, and centromere (C)-banding, still contribute greatly by being used as a routine procedure in clinical cytogenetic laboratory nowadays. Each chromosome has a unique sequence of bar code-like stripes, allowing the identification of individual homologues and the recognition of structural abnormalities through analyzing the disruption of the normal banding pattern at specific landmarks, regions, and bands as described in the ideogram. Since the quality of metaphases obtained from malignant cells is generally inferior to normal constitutional cells for karyotyping, a practical and accurate chromosome identification training guide is indispensable for a trainee or newly employed cytogenetic technologist in a cancer cytogenetic laboratory. The most common and currently used banding methods and chromosome recognition guide for distinguishable bands of each chromosome are described in detail in this chapter with an aim to facilitate quick and accurate karyotyping in cancer cells.
Collapse
Affiliation(s)
- Thomas S K Wan
- Division of Molecular Pathology, Department of Pathology, Hong Kong Sanatorium & Hospital, Hong Kong, People's Republic of China.
| | - Edmond S K Ma
- Division of Molecular Pathology, Department of Pathology, Hong Kong Sanatorium & Hospital, Hong Kong, People's Republic of China
| |
Collapse
|
2
|
Brovkina MV, Chapman MA, Holding ML, Clowney EJ. Emergence and influence of sequence bias in evolutionarily malleable, mammalian tandem arrays. BMC Biol 2023; 21:179. [PMID: 37612705 PMCID: PMC10463633 DOI: 10.1186/s12915-023-01673-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Accepted: 08/01/2023] [Indexed: 08/25/2023] Open
Abstract
BACKGROUND The radiation of mammals at the extinction of the dinosaurs produced a plethora of new forms-as diverse as bats, dolphins, and elephants-in only 10-20 million years. Behind the scenes, adaptation to new niches is accompanied by extensive innovation in large families of genes that allow animals to contact the environment, including chemosensors, xenobiotic enzymes, and immune and barrier proteins. Genes in these "outward-looking" families are allelically diverse among humans and exhibit tissue-specific and sometimes stochastic expression. RESULTS Here, we show that these tandem arrays of outward-looking genes occupy AT-biased isochores and comprise the "tissue-specific" gene class that lack CpG islands in their promoters. Models of mammalian genome evolution have not incorporated the sharply different functions and transcriptional patterns of genes in AT- versus GC-biased regions. To examine the relationship between gene family expansion, sequence content, and allelic diversity, we use population genetic data and comparative analysis. First, we find that AT bias can emerge during evolutionary expansion of gene families in cis. Second, human genes in AT-biased isochores or with GC-poor promoters experience relatively low rates of de novo point mutation today but are enriched for non-synonymous variants. Finally, we find that isochores containing gene clusters exhibit low rates of recombination. CONCLUSIONS Our analyses suggest that tolerance of non-synonymous variation and low recombination are two forces that have produced the depletion of GC bases in outward-facing gene arrays. In turn, high AT content exerts a profound effect on their chromatin organization and transcriptional regulation.
Collapse
Affiliation(s)
- Margarita V Brovkina
- Graduate Program in Cellular and Molecular Biology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Margaret A Chapman
- Neurosciences Graduate Program, University of Michigan Medical School, Ann Arbor, MI, USA
| | | | - E Josephine Clowney
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, USA.
- Michigan Neuroscience Institute, University of Michigan, Ann Arbor, MI, USA.
| |
Collapse
|
3
|
Dwiranti A, Mualifah M, Kartapradja RHDH, Abinawanto A, Salamah A, Fukui K. Insight into magnesium ions effect on chromosome banding and ultrastructure. Microsc Res Tech 2022; 85:3356-3364. [PMID: 35765224 DOI: 10.1002/jemt.24190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2022] [Revised: 06/04/2022] [Accepted: 06/20/2022] [Indexed: 11/08/2022]
Abstract
Magnesium ion (Mg2+ ) plays a fundamental role in chromosome condensation which is important for genetic material segregation. Studies about the effects of Mg2+ on the overall chromosome structure have been reported. Nevertheless, its effects on the distribution of heterochromatin and euchromatin region have yet to be investigated. The aim of this study was to evaluate the effects of Mg2+ on the banding pattern and ultrastructure of the chromosome. Chromosome analysis was performed using the synchronized HeLa cells. The effect of Mg2+ was evaluated by subjecting the chromosomes to three different solutions, namely XBE5 (containing 5 mM Mg2+ ) as a control, XBE (0 mM Mg2+ ), and 1 mM EDTA as cations-chelator. Chromosome banding was carried out using the GTL-banding technique. The ultrastructure of the chromosomes treated with and without Mg2+ was further obtained using SEM. The results showed a condensed chromosome structure with a clear banding pattern when the chromosomes were treated with a buffer containing 5 mM Mg2+ . In contrast, chromosomes treated with a buffer containing no Mg2+ and those treated with a cations-chelator showed an expanded and fibrous structure with the lower intensity of the banding pattern. Elongation of the chromosome caused by decondensation resulted in the band splitting. The different ultrastructure of the chromosomes treated with and without Mg2+ was obvious under SEM. The results of this study further emphasized the role of Mg2+ on chromosome structure and gave insights into Mg2+ effects on the banding distribution and ultrastructure of the chromosome.
Collapse
Affiliation(s)
- Astari Dwiranti
- Cellular and Molecular Mechanisms in Biological System Research Group, Department of Biology, Faculty of Mathematics and Natural Sciences, Universitas Indonesia, Depok, Indonesia
| | - Mualifah Mualifah
- Cellular and Molecular Mechanisms in Biological System Research Group, Department of Biology, Faculty of Mathematics and Natural Sciences, Universitas Indonesia, Depok, Indonesia
| | | | - Abinawanto Abinawanto
- Cellular and Molecular Mechanisms in Biological System Research Group, Department of Biology, Faculty of Mathematics and Natural Sciences, Universitas Indonesia, Depok, Indonesia
| | - Andi Salamah
- Cellular and Molecular Mechanisms in Biological System Research Group, Department of Biology, Faculty of Mathematics and Natural Sciences, Universitas Indonesia, Depok, Indonesia
| | - Kiichi Fukui
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Japan
| |
Collapse
|
4
|
Serna-Pujol N, Salinas-Pena M, Mugianesi F, Lopez-Anguita N, Torrent-Llagostera F, Izquierdo-Bouldstridge A, Marti-Renom MA, Jordan A. TADs enriched in histone H1.2 strongly overlap with the B compartment, inaccessible chromatin, and AT-rich Giemsa bands. FEBS J 2020; 288:1989-2013. [PMID: 32896099 DOI: 10.1111/febs.15549] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 07/22/2020] [Accepted: 09/01/2020] [Indexed: 01/04/2023]
Abstract
Giemsa staining of metaphase chromosomes results in a characteristic banding useful for identification of chromosomes and its alterations. We have investigated in silico whether Giemsa bands (G bands) correlate with epigenetic and topological features of the interphase genome. Staining of G-positive bands decreases with GC content; nonetheless, G-negative bands are GC heterogeneous. High GC bands are enriched in active histone marks, RNA polymerase II, and SINEs and associate with gene richness, gene expression, and early replication. Low GC bands are enriched in repressive marks, lamina-associated domains, and LINEs. Histone H1 variants distribute heterogeneously among G bands: H1X is enriched at high GC bands and H1.2 is abundant at low GC, compacted bands. According to epigenetic features and H1 content, G bands can be organized in clusters useful to compartmentalize the genome. Indeed, we have obtained Hi-C chromosome interaction maps and compared topologically associating domains (TADs) and A/B compartments to G banding. TADs with high H1.2/H1X ratio strongly overlap with B compartment, late replicating, and inaccessible chromatin and low GC bands. We propose that GC content is a strong driver of chromatin compaction and 3D genome organization, that Giemsa staining recapitulates this organization denoted by high-throughput techniques, and that H1 variants distribute at distinct chromatin domains. DATABASES: Hi-C data on T47D breast cancer cells have been deposited in NCBI's Gene Expression Omnibus and are accessible through GEO Series accession number GSE147627.
Collapse
Affiliation(s)
| | | | - Francesca Mugianesi
- CNAG-CRG, Centre for Genomic Regulation, The Barcelona Institute of Science and Technology, Spain
| | | | | | | | - Marc A Marti-Renom
- CNAG-CRG, Centre for Genomic Regulation, The Barcelona Institute of Science and Technology, Spain.,Centre for Genomic Regulation, The Barcelona Institute for Science and Technology, Spain.,Pompeu Fabra University, Barcelona, Spain.,ICREA, Barcelona, Spain
| | - Albert Jordan
- Molecular Biology Institute of Barcelona (IBMB-CSIC), Spain
| |
Collapse
|
5
|
Tan ZW, Guarnera E, Berezovsky IN. Exploring chromatin hierarchical organization via Markov State Modelling. PLoS Comput Biol 2018; 14:e1006686. [PMID: 30596637 PMCID: PMC6355033 DOI: 10.1371/journal.pcbi.1006686] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Revised: 01/31/2019] [Accepted: 11/27/2018] [Indexed: 01/02/2023] Open
Abstract
We propose a new computational method for exploring chromatin structural organization based on Markov State Modelling of Hi-C data represented as an interaction network between genomic loci. A Markov process describes the random walk of a traveling probe in the corresponding energy landscape, mimicking the motion of a biomolecule involved in chromatin function. By studying the metastability of the associated Markov State Model upon annealing, the hierarchical structure of individual chromosomes is observed, and corresponding set of structural partitions is identified at each level of hierarchy. Then, the notion of effective interaction between partitions is derived, delineating the overall topology and architecture of chromosomes. Mapping epigenetic data on the graphs of intra-chromosomal effective interactions helps in understanding how chromosome organization facilitates its function. A sketch of whole-genome interactions obtained from the analysis of 539 partitions from all 23 chromosomes, complemented by distributions of gene expression regulators and epigenetic factors, sheds light on the structure-function relationships in chromatin, delineating chromosomal territories, as well as structural partitions analogous to topologically associating domains and active / passive epigenomic compartments. In addition to the overall genome architecture shown by effective interactions, the affinity between partitions of different chromosomes was analyzed as an indicator of the degree of association between partitions in functionally relevant genomic interactions. The overall static picture of whole-genome interactions obtained with the method presented in this work provides a foundation for chromatin structural reconstruction, for the modelling of chromatin dynamics, and for exploring the regulation of genome function. The algorithms used in this study are implemented in a freely available Python package ChromaWalker (https://bitbucket.org/ZhenWahTan/chromawalker).
Collapse
Affiliation(s)
- Zhen Wah Tan
- Bioinformatics Institute (BII), Agency for Science, Technology and Research (A*STAR), Matrix, Singapore
| | - Enrico Guarnera
- Bioinformatics Institute (BII), Agency for Science, Technology and Research (A*STAR), Matrix, Singapore
| | - Igor N. Berezovsky
- Bioinformatics Institute (BII), Agency for Science, Technology and Research (A*STAR), Matrix, Singapore
- Department of Biological Sciences (DBS), National University of Singapore (NUS), Singapore
| |
Collapse
|
6
|
Costantini M, Musto H. The Isochores as a Fundamental Level of Genome Structure and Organization: A General Overview. J Mol Evol 2017; 84:93-103. [PMID: 28243687 DOI: 10.1007/s00239-017-9785-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Accepted: 02/15/2017] [Indexed: 11/30/2022]
Abstract
The recent availability of a number of fully sequenced genomes (including marine organisms) allowed to map very precisely the isochores, based on DNA sequences, confirming the results obtained before genome sequencing by the ultracentrifugation in CsCl. In fact, the analytical profile of human DNA showed that the vertebrate genome is a mosaic of isochores, typically megabase-size DNA segments that belong to a small number of families characterized by different GC levels. In this review, we will concentrate on some general genome features regarding the compositional organization from different organisms and their evolution, ranging from vertebrates to invertebrates until unicellular organisms. Since isochores are tightly linked to biological properties such as gene density, replication timing, and recombination, the new level of detail provided by the isochore map helped the understanding of genome structure, function, and evolution. All the findings reported here confirm the idea that the isochores can be considered as a "fundamental level of genome structure and organization." We stress that we do not discuss in this review the origin of isochores, which is still a matter of controversy, but we focus on well established structural and physiological aspects.
Collapse
Affiliation(s)
- Maria Costantini
- Department of Biology and Evolution of Marine Organisms, Stazione Zoologica Anton Dohrn, Villa Comunale, 80121, Napoli, Italy.
| | - Héctor Musto
- Laboratorio de Organización y Evolución del Genoma, Unidad de Genómica Evolutiva, Facultad de Ciencias, 11400, Montevideo, Uruguay
| |
Collapse
|
7
|
Baker MS, Ahn SB, Mohamedali A, Islam MT, Cantor D, Verhaert PD, Fanayan S, Sharma S, Nice EC, Connor M, Ranganathan S. Accelerating the search for the missing proteins in the human proteome. Nat Commun 2017; 8:14271. [PMID: 28117396 PMCID: PMC5286205 DOI: 10.1038/ncomms14271] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 12/06/2016] [Indexed: 12/25/2022] Open
Abstract
The Human Proteome Project (HPP) aims to discover high-stringency data for all proteins encoded by the human genome. Currently, ∼18% of the proteins in the human proteome (the missing proteins) do not have high-stringency evidence (for example, mass spectrometry) confirming their existence, while much additional information is available about many of these missing proteins. Here, we present MissingProteinPedia as a community resource to accelerate the discovery and understanding of these missing proteins. The Human Proteome Project aims to catalogue the ∼20,000 proteins encoded by the human genome. In this review, Baker et al . focus on the missing proteins, proteins that lack high stringency proteomic evidence, and launch MissingProteinPedia, a database aimed at accelerating the search for missing proteins.
Collapse
Affiliation(s)
- Mark S. Baker
- Department of Biomedical Sciences, Faculty of Medicine & Health Sciences, Macquarie University, New South Wales 2109, Australia
| | - Seong Beom Ahn
- Department of Biomedical Sciences, Faculty of Medicine & Health Sciences, Macquarie University, New South Wales 2109, Australia
| | - Abidali Mohamedali
- Department of Biomedical Sciences, Faculty of Medicine & Health Sciences, Macquarie University, New South Wales 2109, Australia
- Department of Chemistry & Biomolecular Sciences, Macquarie University, New South Wales 2109, Australia
| | - Mohammad T. Islam
- Department of Chemistry & Biomolecular Sciences, Macquarie University, New South Wales 2109, Australia
| | - David Cantor
- Department of Biomedical Sciences, Faculty of Medicine & Health Sciences, Macquarie University, New South Wales 2109, Australia
| | | | - Susan Fanayan
- Department of Biomedical Sciences, Faculty of Medicine & Health Sciences, Macquarie University, New South Wales 2109, Australia
| | - Samridhi Sharma
- Department of Biomedical Sciences, Faculty of Medicine & Health Sciences, Macquarie University, New South Wales 2109, Australia
| | - Edouard C. Nice
- Department of Biochemistry and Molecular Biology, Monash University, Victoria 3800, Australia
| | - Mark Connor
- Department of Biomedical Sciences, Faculty of Medicine & Health Sciences, Macquarie University, New South Wales 2109, Australia
| | - Shoba Ranganathan
- Department of Chemistry & Biomolecular Sciences, Macquarie University, New South Wales 2109, Australia
| |
Collapse
|
8
|
Amarillo IE, Nievera I, Hagan A, Huchthagowder V, Heeley J, Hollander A, Koenig J, Austin P, Wang T. Integrated small copy number variations and epigenome maps of disorders of sex development. Hum Genome Var 2016; 3:16012. [PMID: 27340555 PMCID: PMC4899613 DOI: 10.1038/hgv.2016.12] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Revised: 03/24/2016] [Accepted: 03/26/2016] [Indexed: 02/03/2023] Open
Abstract
Small copy number variations (CNVs) have typically not been analyzed or reported in clinical settings and hence have remained underrepresented in databases and the literature. Here, we focused our investigations on these small CNVs using chromosome microarray analysis (CMA) data previously obtained from patients with atypical characteristics or disorders of sex development (DSD). Using our customized CMA track targeting 334 genes involved in the development of urogenital and reproductive structures and a less stringent analysis filter, we uncovered small genes with recurrent and overlapping CNVs as small as 1 kb, and small regions of homozygosity (ROHs), imprinting and position effects. Detailed analysis of these high-resolution data revealed CNVs and ROHs involving structural and functional domains, repeat elements, active transcription sites and regulatory regions. Integration of these genomic data with DNA methylation, histone modification and predicted RNA expression profiles in normal testes and ovaries suggested spatiotemporal and tissue-specific gene regulation. This study emphasized a DSD-specific and gene-targeted CMA approach that uncovered previously unanalyzed or unreported small genes and CNVs, contributing to the growing resources on small CNVs and facilitating the narrowing of the genomic gap for identifying candidate genes or regions. This high-resolution analysis tool could improve the diagnostic utility of CMA, not only in patients with DSD but also in other clinical populations. These integrated data provided a better genomic-epigenomic landscape of DSD and greater opportunities for downstream research.
Collapse
Affiliation(s)
- Ina E Amarillo
- Cytogenomics and Molecular Pathology Laboratory, Division of Laboratory and Genomic Medicine, Department of Pathology and Immunology, Washington University in St Louis School of Medicine, St Louis, MO, USA; Washington University in St Louis School of Medicine DSD Team, St Louis, MO, USA
| | - Isabelle Nievera
- Washington University in St Louis School of Medicine DSD Team , St Louis, MO, USA
| | - Andrew Hagan
- Division of Biology and Biomedical Sciences, Washington University in St Louis , St Louis, MO, USA
| | - Vishwa Huchthagowder
- Cytogenomics and Molecular Pathology Laboratory, Division of Laboratory and Genomic Medicine, Department of Pathology and Immunology, Washington University in St Louis School of Medicine , St Louis, MO, USA
| | - Jennifer Heeley
- Washington University in St Louis School of Medicine DSD Team, St Louis, MO, USA; Department of Pediatrics, Washington University in St Louis School of Medicine, St Louis, MO, USA
| | - Abby Hollander
- Washington University in St Louis School of Medicine DSD Team, St Louis, MO, USA; Department of Pediatrics, Washington University in St Louis School of Medicine, St Louis, MO, USA
| | - Joel Koenig
- Washington University in St Louis School of Medicine DSD Team, St Louis, MO, USA; Department of Surgery, Washington University in St Louis School of Medicine, St Louis, MO, USA
| | - Paul Austin
- Washington University in St Louis School of Medicine DSD Team, St Louis, MO, USA; Department of Surgery, Washington University in St Louis School of Medicine, St Louis, MO, USA
| | - Ting Wang
- Department of Genetics, Washington University in St Louis School of Medicine , St Louis, MO, USA
| |
Collapse
|
9
|
Integration of HIV in the Human Genome: Which Sites Are Preferential? A Genetic and Statistical Assessment. Int J Genomics 2016; 2016:2168590. [PMID: 27294106 PMCID: PMC4880676 DOI: 10.1155/2016/2168590] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Accepted: 04/24/2016] [Indexed: 12/17/2022] Open
Abstract
Chromosomal fragile sites (FSs) are loci where gaps and breaks may occur and are preferential integration targets for some viruses, for example, Hepatitis B, Epstein-Barr virus, HPV16, HPV18, and MLV vectors. However, the integration of the human immunodeficiency virus (HIV) in Giemsa bands and in FSs is not yet completely clear. This study aimed to assess the integration preferences of HIV in FSs and in Giemsa bands using an in silico study. HIV integration positions from Jurkat cells were used and two nonparametric tests were applied to compare HIV integration in dark versus light bands and in FS versus non-FS (NFSs). The results show that light bands are preferential targets for integration of HIV-1 in Jurkat cells and also that it integrates with equal intensity in FSs and in NFSs. The data indicates that HIV displays different preferences for FSs compared to other viruses. The aim was to develop and apply an approach to predict the conditions and constraints of HIV insertion in the human genome which seems to adequately complement empirical data.
Collapse
|
10
|
Jabbari K, Nürnberg P. A genomic view on epilepsy and autism candidate genes. Genomics 2016; 108:31-6. [PMID: 26772991 DOI: 10.1016/j.ygeno.2016.01.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Revised: 12/15/2015] [Accepted: 01/01/2016] [Indexed: 01/25/2023]
Abstract
Epilepsy is a common complex disorder most frequently associated with psychiatric and neurological diseases. Massive parallel sequencing of individual or cohort genomes and exomes led the identification of several disease associated genes. We review here the candidate genes in epilepsy genetics with focus on exome and gene panel data. Together with the examination of brain expressed genes and post synaptic proteome the results show that: (1) Non-metabolic epilepsies and autism candidate genes tend to be AT-rich and (2) large transcript size and local AT-richness are characteristic features of genes involved in developmental brain disorders and synaptic functions. These results point to the preferential location of core epilepsy and autism candidate genes in late replicating, GC-poor chromosomal regions (isochores). These results indicate that the genomic alterations leading to some brain disorders are confined to responsive chromatin areas harboring brain critical genes.
Collapse
Affiliation(s)
- Kamel Jabbari
- Cologne Center for Genomics, University of Cologne, Cologne, Germany.
| | - Peter Nürnberg
- Cologne Center for Genomics, University of Cologne, Cologne, Germany
| |
Collapse
|
11
|
Copy Number Studies in Noisy Samples. MICROARRAYS 2013; 2:284-303. [PMID: 27605193 PMCID: PMC5003442 DOI: 10.3390/microarrays2040284] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/20/2013] [Revised: 10/24/2013] [Accepted: 10/25/2013] [Indexed: 11/17/2022]
Abstract
System noise was analyzed in 77 Affymetrix 6.0 samples from a previous clinical study of copy number variation (CNV). Twenty-three samples were classified as eligible for CNV detection, 29 samples as ineligible and 25 were classified as being of intermediate quality. New software (“noise-free-cnv”) was developed to visualize the data and reduce system noise. Fresh DNA preparations were more likely to yield eligible samples (p < 0.001). Eligible samples had higher rates of successfully genotyped SNPs (p < 0.001) and lower variance of signal intensities (p < 0.001), yielded fewer CNV findings after Birdview analysis (p < 0.001), and showed a tendency to yield fewer PennCNV calls (p = 0.053). The noise-free-cnv software visualized trend patterns of noise in the signal intensities across the ordered SNPs, including a wave pattern of noise, being co-linear with the banding pattern of metaphase chromosomes, as well as system deviations of individual probe sets (per-SNP noise). Wave noise and per-SNP noise occurred independently and could be separately removed from the samples. We recommend a two-step procedure of CNV validation, including noise reduction and visual inspection of all CNV calls, prior to molecular validation of a selected number of putative CNVs.
Collapse
|
12
|
Rubtsov NB. Organization of eukaryotic chromosomes: From Kol’tsov’s studies up to present day. RUSS J GENET+ 2013. [DOI: 10.1134/s1022795413010109] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
13
|
Morozkin ES, Loseva EM, Karamysheva TV, Babenko VN, Laktionov PP, Vlassov VV, Rubtsov NB. A method for generating selective DNA probes for the analysis of C-negative regions in human chromosomes. Cytogenet Genome Res 2011; 135:1-11. [PMID: 21811056 DOI: 10.1159/000330124] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/18/2011] [Indexed: 12/14/2022] Open
Abstract
Linker-adapter polymerase chain reaction (LA-PCR) is among the most efficient techniques for whole genome DNA amplification. The key stage in LA-PCR is the hydrolysis of a DNA sample with restriction endonucleases, and the choice of a restriction endonuclease (or several endonucleases) determines the composition of DNA probes generated in LA-PCR. Computer analysis of the localization of the restriction sites in human genome has allowed us to propose an efficient technique for generating DNA probes by LA-PCR using the restriction endonucleases HaeIII and RsaI. In silico hydrolysis of human genomic DNA with endonucleases HaeIII and RsaI demonstrate that 100- to 1,000-bp DNA fragments are more abundant in the gene-rich regions. Applying in situ hybridization to metaphase chromosomes, we demonstrated that the produced DNA probes predominantly hybridized to the C-negative chromosomal regions, whereas the FISH signal was almost absent in the C-positive regions. The described protocol for generating DNA probes may be successfully used in subsequent cytogenetic analysis of the C-negative chromosomal regions.
Collapse
Affiliation(s)
- E S Morozkin
- Institute of Chemical Biology and Fundamental Medicine, Siberian Division, Russian Academy of Sciences, Novosibirsk. morozkin @ niboch.nsc.ru
| | | | | | | | | | | | | |
Collapse
|
14
|
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]
|
15
|
Pelliccia F, Bosco N, Rocchi A. Breakages at common fragile sites set boundaries of amplified regions in two leukemia cell lines K562 - Molecular characterization of FRA2H and localization of a new CFS FRA2S. Cancer Lett 2010; 299:37-44. [PMID: 20851513 DOI: 10.1016/j.canlet.2010.08.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2010] [Revised: 08/04/2010] [Accepted: 08/09/2010] [Indexed: 11/18/2022]
Abstract
Genome amplification is often observed in human tumors. The breakage-fusion-bridge (BFB) cycle is the mechanism that often underlies duplicated regions. Some research has indicated common fragile sites (CFS) as possible sites of chromosome breakages at the origin of BFB cycles. Here we searched two human genome regions known as amplification hot spots for any DNA copy number amplifications by analyzing 21 cancer cell lines to investigate the relationship between genomic fragility and amplification. We identified a duplicated region on a chromosomes der(2) present in the karyotype of two analysed leukemia cell lines K562. The two duplicated regions are organized into large palindromes, which suggests that one BFB cycle has occurred. Our findings show that the three breakpoints are localized in the sequence of three CFSs: FRA2H (2q32.1-q32.2), which here has been characterized molecularly; FRA2S (2q22.3-q23.3), a newly localized aphidicolin inducible CFS; and FRA2G (2q24.3-q31).
Collapse
Affiliation(s)
- Franca Pelliccia
- Dipartimento di Genetica e Biologia Molecolare, Università La Sapienza, P.le Aldo Moro 5, 00185 Roma, Italy.
| | | | | |
Collapse
|
16
|
Abstract
Using a methylated-DNA enrichment technique (methylated CpG island recovery assay, MIRA) in combination with whole-genome tiling arrays, we have characterized by MIRA-chip the entire B cell "methylome" of an individual human at 100-bp resolution. We find that at the chromosome level high CpG methylation density is correlated with subtelomeric regions and Giemsa-light bands (R bands). The majority of the most highly methylated regions that could be identified on the tiling arrays were associated with genes. Approximately 10% of all promoters in B cells were found to be methylated, and this methylation correlates with low gene expression. Notably, apparent exceptions to this correlation were the result of transcription from previously unidentified, unmethylated transcription start sites, suggesting that methylation may control alternate promoter usage. Methylation of intragenic (gene body) sequences was found to correlate with increased, not decreased, transcription, and a methylated region near the 3' end was found in approximately 12% of all genes. The majority of broad regions (10-44 kb) of high methylation were at segmental duplications. Our data provide a valuable resource for the analysis of CpG methylation patterns in a differentiated human cell type and provide new clues regarding the function of mammalian DNA methylation.
Collapse
|
17
|
Kowalska A, Bozsaky E, Ramsauer T, Rieder D, Bindea G, Lörch T, Trajanoski Z, Ambros PF. A new platform linking chromosomal and sequence information. Chromosome Res 2007; 15:327-39. [PMID: 17406992 DOI: 10.1007/s10577-007-1129-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2006] [Revised: 01/24/2007] [Accepted: 01/24/2007] [Indexed: 10/23/2022]
Abstract
We have tested whether a direct correlation of sequence information and staining properties of chromosomes is possible and whether this combined information can be used to precisely map any position on the chromosome. Despite huge differences of compaction between the naked DNA and the DNA packed in chromosomes we found a striking correlation when visualizing the GGCC density on both levels. Software was developed that allows one to superimpose chromosomal fluorescence intensity profiles generated by chromolysin A3 (CMA3) staining with GGCC density extracted from the Ensembl database. Thus, any position along the chromosome can be defined in megabase pairs (Mb) besides the cytoband information, enabling direct alignment of chromosomal information with the sequence data. The mapping tool was validated using 13 different BAC clones, resulting in a mean difference from Ensembl data of 2 Mb (ranging from 0.79 to 3.57 Mb). Our results indicate that the sequence density information and information gained with sequence-specific fluorochromes are superimposable. Thus, the visualized GGCC motif density along the chromosome (sequence bands) provides a unique platform for comparing different types of genomic information.
Collapse
Affiliation(s)
- Agata Kowalska
- CCRI, Children's Cancer Research Institute, St. Anna Kinderkrebsforschung, 1090, Vienna, Austria
| | | | | | | | | | | | | | | |
Collapse
|
18
|
Curatolo A, Limongi ZM, Pelliccia F, Rocchi A. Molecular characterization of the human common fragile site FRA1H. Genes Chromosomes Cancer 2007; 46:487-93. [PMID: 17311248 DOI: 10.1002/gcc.20432] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The molecular basis of the fragility of common fragile sites (CFS) and their role in chromosome instability and in altered expression of associated genes in cancer cells have not yet been clarified. In the present work we analyzed the human CFS FRA1H. FRA1H is the first characterized CFS the expression of which is not induced by aphidicolin but instead by DAPI. 5-azaC, 5-azadC, and Ad12 induce a CFS with the same cytogenetic location. By using FISH analysis with BAC clones, we determined that this CFS extends for approximately 10 Mb, and is therefore one of the largest characterized CFSs. FRA1H maps to the chromosome bands 1q41 and 1q42.1 thus spanning an R-band/G-band boundary, a region considered difficult to duplicate. The FRA1H DNA sequence was analyzed to identify coding sequences, the AT content, the type and quantity of the DNA repeats, the CpG islands, the matrix attachment regions, and the number and distribution of high-flexibility regions. A 120 kb long sequence was identified that is very AT-rich (64.6%), has a very large number of flexibility peaks and that may be involved in inducing fragility in the surrounding regions. Among the other genes, two very large genes (USH2A, ESRRG) and two microRNA genes (MIRN194-1, MIRN215) map within the fragile region.
Collapse
Affiliation(s)
- Angela Curatolo
- Dipartimento di Genetica e Biologia Molecolare, Universita, La Sapienza, 00185 Roma, Italia
| | | | | | | |
Collapse
|
19
|
Cohen SM, Furey TS, Doggett NA, Kaufman DG. Genome-wide sequence and functional analysis of early replicating DNA in normal human fibroblasts. BMC Genomics 2006; 7:301. [PMID: 17134498 PMCID: PMC1702361 DOI: 10.1186/1471-2164-7-301] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2006] [Accepted: 11/29/2006] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND The replication of mammalian genomic DNA during the S phase is a highly coordinated process that occurs in a programmed manner. Recent studies have begun to elucidate the pattern of replication timing on a genomic scale. Using a combination of experimental and computational techniques, we identified a genome-wide set of the earliest replicating sequences. This was accomplished by first creating a cosmid library containing DNA enriched in sequences that replicate early in the S phase of normal human fibroblasts. Clone ends were then sequenced and aligned to the human genome. RESULTS By clustering adjacent or overlapping early replicating clones, we identified 1759 "islands" averaging 100 kb in length, allowing us to perform the most detailed analysis to date of DNA characteristics and genes contained within early replicating DNA. Islands are enriched in open chromatin, transcription related elements, and Alu repetitive elements, with an underrepresentation of LINE elements. In addition, we found a paucity of LTR retroposons, DNA transposon sequences, and an enrichment in all classes of tandem repeats, except for dinucleotides. CONCLUSION An analysis of genes associated with islands revealed that nearly half of all genes in the WNT family, and a number of genes in the base excision repair pathway, including four of ten DNA glycosylases, were associated with island sequences. Also, we found an overrepresentation of members of apoptosis-associated genes in very early replicating sequences from both fibroblast and lymphoblastoid cells. These data suggest that there is a temporal pattern of replication for some functionally related genes.
Collapse
Affiliation(s)
- Stephanie M Cohen
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | - Terrence S Furey
- Institute for Genome Sciences and Policy, Duke University, Durham, NC, 27708, USA
| | - Norman A Doggett
- Bioscience Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - David G Kaufman
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| |
Collapse
|
20
|
Li W, Miramontes P. Large-scale oscillation of structure-related DNA sequence features in human chromosome 21. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2006; 74:021912. [PMID: 17025477 DOI: 10.1103/physreve.74.021912] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2006] [Indexed: 05/12/2023]
Abstract
Human chromosome 21 is the only chromosome in the human genome that exhibits oscillation of the (G+C) content of a cycle length of hundreds kilobases (kb) ( 500 kb near the right telomere). We aim at establishing the existence of a similar periodicity in structure-related sequence features in order to relate this (G+C)% oscillation to other biological phenomena. The following quantities are shown to oscillate with the same 500 kb periodicity in human chromosome 21: binding energy calculated by two sets of dinucleotide-based thermodynamic parameters, AA/TT and AAA/TTT bi- and tri-nucleotide density, 5'-TA-3' dinucleotide density, and signal for 10- or 11-base periodicity of AA/TT or AAA/TTT. These intrinsic quantities are related to structural features of the double helix of DNA molecules, such as base-pair binding, untwisting or unwinding, stiffness, and a putative tendency for nucleosome formation.
Collapse
Affiliation(s)
- Wentian Li
- The Robert S. Boas Center for Genomics and Human Genetics, Feinstein Institute for Medical Research, North Shore LIJ Health System, 350 Community Drive, Manhasset, New York 11030, USA.
| | | |
Collapse
|
21
|
Berger R. [Human cytogenetics. From 1956 to 2006]. ACTA ACUST UNITED AC 2006; 55:1-12. [PMID: 16697121 DOI: 10.1016/j.patbio.2006.04.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2006] [Accepted: 04/05/2006] [Indexed: 01/24/2023]
Abstract
The correct enumeration of human chromosomes, only established in 1956, has marked the starting point of the modern cytogenetics. The introduction of banding techniques, then of in situ hybridization techniques, and now of genomic microarray technology allowed a dramatic development of cytogenetics of which the main applications to basic and medical research are evoked in this review.
Collapse
Affiliation(s)
- R Berger
- Hôpital Necker-Enfants-Malades, EMI 0210 Inserm, 149, rue de Sèvres, 75743 Paris cedex 15, France.
| |
Collapse
|
22
|
Shrimpton AE, Jensen KA, Hoo JJ. Karyotype–phenotype analysis and molecular delineation of a 3p26 deletion/8q24.3 duplication case with a virtually normal phenotype and mild cognitive deficit. Am J Med Genet A 2006; 140:388-91. [PMID: 16411192 DOI: 10.1002/ajmg.a.31066] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
23
|
Li W, Holste D. Universal 1/f noise, crossovers of scaling exponents, and chromosome-specific patterns of guanine-cytosine content in DNA sequences of the human genome. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2005; 71:041910. [PMID: 15903704 DOI: 10.1103/physreve.71.041910] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2004] [Revised: 10/28/2004] [Indexed: 05/02/2023]
Abstract
Spatial fluctuations of guanine and cytosine base content (GC%) are studied by spectral analysis for the complete set of human genomic DNA sequences. We find that (i) 1/ f(alpha) decay is universally observed in the power spectra of all 24 chromosomes, and (ii) the exponent alpha approximately 1 extends to about 10(7) bases, one order of magnitude longer than has previously been observed. We further find that (iii) almost all human chromosomes exhibit a crossover from alpha(1) approximately 1 (1/ f (alpha(1))) at lower frequency to alpha(2) <1 (1/ f (alpha(2))) at higher frequency, typically occurring at around 30,000-100,000 bases, while (iv) the crossover in this frequency range is virtually absent in human chromosome 22. In addition to the universal 1/ f(alpha) noise in power spectra, we find (v) several lines of evidence for chromosome-specific correlation structures, including a 500,000 base long oscillation in human chromosome 21. The universal 1/ f(alpha) spectrum in the human genome is further substantiated by a resistance to reduction in variance of guanine and cytosine content when the window size is increased.
Collapse
Affiliation(s)
- Wentian Li
- The Robert S. Boas Center for Genomics and Human Genetics, North Shore LIJ Institute for Medical Research, 350 Community Drive, Manhasset, New York 10030, USA.
| | | |
Collapse
|
24
|
Webster MT, Smith NGC, Hultin-Rosenberg L, Arndt PF, Ellegren H. Male-driven biased gene conversion governs the evolution of base composition in human alu repeats. Mol Biol Evol 2005; 22:1468-74. [PMID: 15772377 DOI: 10.1093/molbev/msi136] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Regional biases in substitution pattern are likely to be responsible for the large-scale variation in base composition observed in vertebrate genomes. However, the evolutionary forces responsible for these biases are still not clearly defined. In order to study the processes of mutation and fixation across the entire human genome, we analyzed patterns of substitution in Alu repeats since their insertion. We also studied patterns of human polymorphism within the repeats. There is a highly significant effect of recombination rate on the pattern of substitution, whereas no such effect is seen on the pattern of polymorphism. These results suggest that regional biases in substitution are caused by biased gene conversion, a process that increases the probability of fixation of mutations that increase GC content. Furthermore, the strongest correlate of substitution patterns is found to be male recombination rates rather than female or sex-averaged recombination rates. This indicates that in addition to sexual dimorphism in recombination rates, the sexes also differ in the relative rates of crossover and gene conversion.
Collapse
Affiliation(s)
- Matthew T Webster
- Department of Evolution, Genomics and Systematics, Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden.
| | | | | | | | | |
Collapse
|
25
|
Takebayashi SI, Sugimura K, Saito T, Sato C, Fukushima Y, Taguchi H, Okumura K. Regulation of replication at the R/G chromosomal band boundary and pericentromeric heterochromatin of mammalian cells. Exp Cell Res 2004; 304:162-74. [PMID: 15707583 DOI: 10.1016/j.yexcr.2004.10.024] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2004] [Revised: 10/17/2004] [Accepted: 10/27/2004] [Indexed: 10/26/2022]
Abstract
Mammalian chromosomes consist of multiple replicons; however, in contrast to yeast, the details of this replication process (origin firing, fork progression and termination) relative to specific chromosomal domains remain unclear. Using direct visualization of DNA fibers, here we show that the rate of replication fork movement typically decreases in the early-mid S phase when the replication fork proceeds through the R/G chromosomal band boundary and pericentromeric heterochromatin. To support this, fluorescence in situ hybridization (FISH)-based replication profiles at the human 1q31.1 (R-band)-32.1 (G-band) regions revealed that replication timing switched around at the putative R/G chromosomal band boundary predicted by marked changes in GC content at the sequence level. Thus, the slowdown of replication fork movement is thought to be the general property of the band boundaries separating the functionally different chromosomal domains. By simultaneous visualization of replication fork movement and pericentromeric heterochromatin sequences on DNA fibers, we observed that this region is duplicated by many replication forks, some of which proceed unidirectionally, that originate from clustered replication origins. We showed that histone hyperacetylation is tightly associated with changes in the replication timing of pericentromeric heterochromatin induced by 5-aza-2'-deoxycytidine treatment. These results suggest that, similar to the yeast system, histone modification is involved in controlling the timing of origin firing in mammals.
Collapse
Affiliation(s)
- Shin-Ichiro Takebayashi
- Laboratory of Molecular and Cellular Biology, Faculty of Bioresources, Mie University, Tsu, Mie 514-8507, Japan.
| | | | | | | | | | | | | |
Collapse
|
26
|
Boon WM, Beissbarth T, Hyde L, Smyth G, Gunnersen J, Denton DA, Scott H, Tan SS. A comparative analysis of transcribed genes in the mouse hypothalamus and neocortex reveals chromosomal clustering. Proc Natl Acad Sci U S A 2004; 101:14972-7. [PMID: 15466702 PMCID: PMC522044 DOI: 10.1073/pnas.0406296101] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The hypothalamus and neocortex are subdivisions of the mammalian forebrain, and yet, they have vastly different evolutionary histories, cytoarchitecture, and biological functions. In an attempt to define these attributes in terms of their genetic activity, we have compared their genetic repertoires by using the Serial Analysis of Gene Expression database. From a comparison of 78,784 hypothalamus tags with 125,296 neocortical tags, we demonstrate that each structure possesses a different transcriptional profile in terms of gene ontological characteristics and expression levels. Despite its more recent evolutionary history, the neocortex has a more complex pattern of gene activity. Gene identities and levels of gene expression were mapped to their chromosomal positions by using in silico definition of GC-rich and GC-poor genome bands. This analysis shows contrasting views of gene activity on a genome scale that is unique to each brain substructure. We show that genes that are more highly expressed in one tissue tend to be clustered together on a chromosomal scale, further defining the genetic identity of either the hypothalamus or neocortex. We propose that physical proximity of coregulated genes may facilitate transcriptional access to the genetic substrates of evolutionary selection that ultimately shape the functional subdivisions of the mammalian brain.
Collapse
Affiliation(s)
- Wee-Ming Boon
- Howard Florey Institute, University of Melbourne, Parkville 3052, Australia
| | | | | | | | | | | | | | | |
Collapse
|
27
|
Shimizu N, Shingaki K. Macroscopic folding and replication of the homogeneously staining region in late S phase leads to the appearance of replication bands in mitotic chromosomes. J Cell Sci 2004; 117:5303-12. [PMID: 15454579 DOI: 10.1242/jcs.01414] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The chromosomal G/R bands are alternating domains differing in their nucleotide sequence biases. The bands are also related to the time of replication: pulse-labeling during S phase makes the replication sites as visible as replication bands that are close to the G/R bands in mitotic chromosomes. We previously showed that a plasmid bearing a mammalian replication origin efficiently generated a chromosomal homogeneously staining region (HSR). Here, we analyze the replication of this artificial HSR and show that it was replicated at the last stage of S phase. The HSR was composed of plasmid repeats only; nonetheless, we found that replication sites pulse-labeled during late S phase appeared as bands in the mitotic HSR and their number was dependent on the length of the HSR. Therefore, replication bands might not arise from sequence information per se. To understand the chronological order of appearance of replication sites, we performed a double pulse-chase experiment using IdU and CldU. Replication of the entire HSR required 100-120 minutes. During this period, the replicated sites appeared as bands at the first and last stages, but in between were apparently scattered along the entire HSR. An analysis of S-phase nuclei revealed that the replication started at the periphery of the globular HSR domain, followed by initiation in the internal domain. The replicated HSR appeared as a ring or a pair of extended spirals in late G2-phase nuclei. To account for these findings, we present a model in which the HSR is folded as a coiled-coil structure that is replicated from the outside to the inside in S phase nuclei.
Collapse
Affiliation(s)
- Noriaki Shimizu
- Faculty of Integrated Arts and Sciences, Hiroshima University, 1-7-1 Kagamiyama, Higashi-hiroshima, 739-8521, Japan.
| | | |
Collapse
|