1
|
Tuszynska I, Bednarz P, Wilczynski B. Effective modeling of the chromatin structure by coarse-grained methods. J Biomol Struct Dyn 2024:1-9. [PMID: 38165232 DOI: 10.1080/07391102.2023.2291176] [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: 09/28/2023] [Accepted: 11/25/2023] [Indexed: 01/03/2024]
Abstract
The interphase chromatin structure is extremely complex, precise and dynamic. Experimental methods can only show the frequency of interaction of the various parts of the chromatin. Therefore, it is extremely important to develop theoretical methods to predict the chromatin structure. In this publication, we implemented an extended version of the SBS model described by Barbieri et al. and created the ChroMC program that is easy to use and freely available (https://github.com/regulomics/chroMC) to other users. We also describe the necessary factors for the effective modeling of the chromatin structure in Drosophila melanogaster. We compared results of chromatin structure predictions using two methods: Monte Carlo and Molecular Dynamic. Our simulations suggest that incorporating black, non-reactive chromatin is necessary for successful prediction of chromatin structure, while the loop extrusion model with a long range attraction potential or Lennard-Jones (with local attraction force) as well as using Hi-C data as input are not essential for the basic structure reconstruction. We also proposed a new way to calculate the similarity of the properties of contact maps including the calculation of local similarity.Communicated by Ramaswamy H. Sarma.
Collapse
Affiliation(s)
- Irina Tuszynska
- Faculty of Mathematics, Informatics and Mechanics, University of Warsaw, Warsaw, Poland
| | - Paweł Bednarz
- Faculty of Mathematics, Informatics and Mechanics, University of Warsaw, Warsaw, Poland
| | - Bartek Wilczynski
- Faculty of Mathematics, Informatics and Mechanics, University of Warsaw, Warsaw, Poland
| |
Collapse
|
2
|
Ravindran SP, Tams V, Cordellier M. Transcriptome‐wide genotype–phenotype associations in
Daphnia
in a predation risk environment. J Evol Biol 2020; 34:879-892. [DOI: 10.1111/jeb.13699] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 08/03/2020] [Accepted: 08/29/2020] [Indexed: 12/30/2022]
Affiliation(s)
- Suda Parimala Ravindran
- Department of Marine Sciences Tjärnö Marine Laboratory University of Gothenburg Strömstad Sweden
| | - Verena Tams
- Institute of Marine Ecosystem and Fishery Science Universität Hamburg Hamburg Germany
| | | |
Collapse
|
3
|
Nikolaou C. Invisible cities: segregated domains in the yeast genome with distinct structural and functional attributes. Curr Genet 2017; 64:247-258. [PMID: 28780612 DOI: 10.1007/s00294-017-0731-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Revised: 07/31/2017] [Accepted: 08/02/2017] [Indexed: 02/07/2023]
Abstract
Recent advances in our understanding of the three-dimensional organization of the eukaryotic nucleus have rendered the spatial distribution of genes increasingly relevant. In a recent work (Tsochatzidou et al., Nucleic Acids Res 45:5818-5828, 2017), we proposed the existence of a functional compartmentalization of the yeast genome according to which, genes occupying the chromosomal regions at the nuclear periphery have distinct structural, functional and evolutionary characteristics compared to their centromeric-proximal counterparts. Around the same time, it was also shown that the genome of Saccharomyces cerevisiae is organized in topologically associated domains (TADs), which are largely associated with the replication timing. In this work, we proceed to investigate whether such units of three-dimensional genomic organization can be linked to transcriptional activity as a driving force for the shaping of genomic architecture. Through the application of a simple boundary-calling criterion in genome-wide 3C data, we define ~100 TAD-like domains which can be clustered in six different classes with radically different nucleosomal organizations, significant variations in transcription factor binding and uneven chromosomal distribution. Approximately ~20% of the genome is found to be confined in regions with "closed" chromatin structure around gene promoters. Most interestingly, we find both "open" and "closed" regions to be segregated, in the sense that they tend to avoid inter-chromosomal interactions. Our data further enforce the notion of a marked compartmentalization of the yeast genome in isolated territories, with implications in its function and evolution.
Collapse
Affiliation(s)
- Christoforos Nikolaou
- Computational Genomics Group, Department of Biology, University of Crete, 70013, Herakleion, Greece.
| |
Collapse
|
4
|
Du M, Bai L. 3D clustering of co-regulated genes and its effect on gene expression. Curr Genet 2017; 63:1017-1021. [PMID: 28551816 DOI: 10.1007/s00294-017-0712-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Revised: 05/22/2017] [Accepted: 05/24/2017] [Indexed: 01/29/2023]
Abstract
There are extensive long-distance chromosomal interactions in eukaryotic genomes, but to what extent these interactions affect gene expression is not clear. Recent works have identified several cases where clustering of co-regulated genes leads to enhanced gene expression in budding yeast. Similar phenomenon was also observed in mammalian cells. These results challenge widely held views of gene regulation in yeast and further our understanding of how the 3D organization of the genome contribute to gene regulation in eukaryotes.
Collapse
Affiliation(s)
- Manyu Du
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, State College, PA, USA.,Center for Eukaryotic Gene Regulation, The Pennsylvania State University, University Park, State College, PA, USA
| | - Lu Bai
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, State College, PA, USA. .,Center for Eukaryotic Gene Regulation, The Pennsylvania State University, University Park, State College, PA, USA. .,Department of Physics, The Pennsylvania State University, University Park, State College, PA, USA.
| |
Collapse
|
5
|
Du M, Zhang Q, Bai L. Three distinct mechanisms of long-distance modulation of gene expression in yeast. PLoS Genet 2017; 13:e1006736. [PMID: 28426659 PMCID: PMC5417705 DOI: 10.1371/journal.pgen.1006736] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Revised: 05/04/2017] [Accepted: 04/05/2017] [Indexed: 12/04/2022] Open
Abstract
Recent Hi-C measurements have revealed numerous intra- and inter-chromosomal interactions in various eukaryotic cells. To what extent these interactions regulate gene expression is not clear. This question is particularly intriguing in budding yeast because it has extensive long-distance chromosomal interactions but few cases of gene regulation over-a-distance. Here, we developed a medium-throughput assay to screen for functional long-distance interactions that affect the average expression level of a reporter gene as well as its cell-to-cell variability (noise). We ectopically inserted an insulated MET3 promoter (MET3pr) flanked by ~1kb invariable sequences into thousands of genomic loci, allowing it to make contacts with different parts of the genome, and assayed the MET3pr activity in single cells. Changes of MET3pr activity in this case necessarily involve mechanisms that function over a distance. MET3pr has similar activities at most locations. However, at some locations, they deviate from the norm and exhibit three distinct patterns including low expression / high noise, low expression / low noise, and high expression / low noise. We provided evidence that these three patterns of MET3pr expression are caused by Sir2-mediated silencing, transcriptional interference, and 3D clustering. The clustering also occurs in the native genome and enhances the transcription of endogenous Met4-targeted genes. Overall, our results demonstrate that a small fraction of long-distance chromosomal interactions can affect gene expression in yeast. Eukaryotic transcription occurs within the nucleus where DNA is packaged into high order chromosome structures. Some long-distance chromosomal interactions play an important role in gene regulation in higher eukaryotic species, such as mouse and human. In budding yeast, gene expression is traditionally thought to be regulated over short distances because the upstream regulatory sequences (URSs) are usually located close to the core promoters. However, recent chromosome conformation capture experiments have detected numerous long-distance chromosomal interactions in the yeast genome. The function of these interactions in gene regulation remains unclear. Here, we developed a new assay to screen for long-distance interactions that affect the activity of a reporter gene. We found three regulatory mechanisms that act from a distance: silencing, transcriptional interference, and 3D clustering, which alter expression level of the reporter gene as well as its cell-to-cell variability. Our results demonstrate that transcription in budding yeast, similar to transcription in higher eukaryotes, can be regulated over long distances. We anticipate our assay can be used as a general platform to screen for functional long-distance chromosomal interactions that affect gene expression.
Collapse
Affiliation(s)
- Manyu Du
- Department of Biochemistry and Molecular Biology, the Pennsylvania State University, University Park, State College, PA, United States of America
- Center for Eukaryotic Gene Regulation, the Pennsylvania State University, University Park, PA, State College, United States of America
| | - Qian Zhang
- Department of Biochemistry and Molecular Biology, the Pennsylvania State University, University Park, State College, PA, United States of America
- Center for Eukaryotic Gene Regulation, the Pennsylvania State University, University Park, PA, State College, United States of America
| | - Lu Bai
- Department of Biochemistry and Molecular Biology, the Pennsylvania State University, University Park, State College, PA, United States of America
- Center for Eukaryotic Gene Regulation, the Pennsylvania State University, University Park, PA, State College, United States of America
- Department of Physics, the Pennsylvania State University, University Park, State College, PA, United States of America
- * E-mail:
| |
Collapse
|
6
|
Carstens S, Nilges M, Habeck M. Inferential Structure Determination of Chromosomes from Single-Cell Hi-C Data. PLoS Comput Biol 2016; 12:e1005292. [PMID: 28027298 PMCID: PMC5226817 DOI: 10.1371/journal.pcbi.1005292] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Revised: 01/11/2017] [Accepted: 12/07/2016] [Indexed: 11/18/2022] Open
Abstract
Chromosome conformation capture (3C) techniques have revealed many fascinating insights into the spatial organization of genomes. 3C methods typically provide information about chromosomal contacts in a large population of cells, which makes it difficult to draw conclusions about the three-dimensional organization of genomes in individual cells. Recently it became possible to study single cells with Hi-C, a genome-wide 3C variant, demonstrating a high cell-to-cell variability of genome organization. In principle, restraint-based modeling should allow us to infer the 3D structure of chromosomes from single-cell contact data, but suffers from the sparsity and low resolution of chromosomal contacts. To address these challenges, we adapt the Bayesian Inferential Structure Determination (ISD) framework, originally developed for NMR structure determination of proteins, to infer statistical ensembles of chromosome structures from single-cell data. Using ISD, we are able to compute structural error bars and estimate model parameters, thereby eliminating potential bias imposed by ad hoc parameter choices. We apply and compare different models for representing the chromatin fiber and for incorporating singe-cell contact information. Finally, we extend our approach to the analysis of diploid chromosome data.
Collapse
Affiliation(s)
- Simeon Carstens
- Unité de Bioinformatique Structurale, Department of Structural Biology and Chemistry, Institut Pasteur, Paris, France
| | - Michael Nilges
- Unité de Bioinformatique Structurale, Department of Structural Biology and Chemistry, Institut Pasteur, Paris, France
| | - Michael Habeck
- Statistical Inverse Problems in Biophysics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
- Felix Bernstein Institute for Mathematical Statistics in the Biosciences, University of Göttingen, Göttingen, Germany
| |
Collapse
|
7
|
Ulianov SV, Gavrilov AA, Razin SV. Nuclear Compartments, Genome Folding, and Enhancer-Promoter Communication. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2015; 315:183-244. [DOI: 10.1016/bs.ircmb.2014.11.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
|
8
|
Rousseau M, Ferraiuolo MA, Crutchley JL, Wang XQ, Miura H, Blanchette M, Dostie J. Classifying leukemia types with chromatin conformation data. Genome Biol 2014; 15:R60. [PMID: 24995990 PMCID: PMC4038739 DOI: 10.1186/gb-2014-15-4-r60] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2014] [Accepted: 04/30/2014] [Indexed: 11/10/2022] Open
Abstract
Background Although genetic or epigenetic alterations have been shown to affect the three-dimensional organization of genomes, the utility of chromatin conformation in the classification of human disease has never been addressed. Results Here, we explore whether chromatin conformation can be used to classify human leukemia. We map the conformation of the HOXA gene cluster in a panel of cell lines with 5C chromosome conformation capture technology, and use the data to train and test a support vector machine classifier named 3D-SP. We show that 3D-SP is able to accurately distinguish leukemias expressing MLL-fusion proteins from those expressing only wild-type MLL, and that it can also classify leukemia subtypes according to MLL fusion partner, based solely on 5C data. Conclusions Our study provides the first proof-of-principle demonstration that chromatin conformation contains the information value necessary for classification of leukemia subtypes.
Collapse
|
9
|
Rousseau M, Crutchley JL, Miura H, Suderman M, Blanchette M, Dostie J. Hox in motion: tracking HoxA cluster conformation during differentiation. Nucleic Acids Res 2014; 42:1524-40. [PMID: 24174538 PMCID: PMC3919592 DOI: 10.1093/nar/gkt998] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Revised: 08/28/2013] [Accepted: 10/02/2013] [Indexed: 12/26/2022] Open
Abstract
Three-dimensional genome organization is an important higher order transcription regulation mechanism that can be studied with the chromosome conformation capture techniques. Here, we combined chromatin organization analysis by chromosome conformation capture-carbon copy, computational modeling and epigenomics to achieve the first integrated view, through time, of a connection between chromatin state and its architecture. We used this approach to examine the chromatin dynamics of the HoxA cluster in a human myeloid leukemia cell line at various stages of differentiation. We found that cellular differentiation involves a transient activation of the 5'-end HoxA genes coinciding with a loss of contacts throughout the cluster, and by specific silencing at the 3'-end with H3K27 methylation. The 3D modeling of the data revealed an extensive reorganization of the cluster between the two previously reported topologically associated domains in differentiated cells. Our results support a model whereby silencing by polycomb group proteins and reconfiguration of CTCF interactions at a topologically associated domain boundary participate in changing the HoxA cluster topology, which compartmentalizes the genes following differentiation.
Collapse
Affiliation(s)
- Mathieu Rousseau
- Department of Biochemistry and Goodman Cancer Research Center, McGill University, Montréal, Québec, H3G 1Y6, Canada and School of Computer Science and McGill Centre for Bioinformatics, McGill University, Montréal, Québec, H3A 0E9, Canada
| | - Jennifer L. Crutchley
- Department of Biochemistry and Goodman Cancer Research Center, McGill University, Montréal, Québec, H3G 1Y6, Canada and School of Computer Science and McGill Centre for Bioinformatics, McGill University, Montréal, Québec, H3A 0E9, Canada
| | - Hisashi Miura
- Department of Biochemistry and Goodman Cancer Research Center, McGill University, Montréal, Québec, H3G 1Y6, Canada and School of Computer Science and McGill Centre for Bioinformatics, McGill University, Montréal, Québec, H3A 0E9, Canada
| | - Matthew Suderman
- Department of Biochemistry and Goodman Cancer Research Center, McGill University, Montréal, Québec, H3G 1Y6, Canada and School of Computer Science and McGill Centre for Bioinformatics, McGill University, Montréal, Québec, H3A 0E9, Canada
| | - Mathieu Blanchette
- Department of Biochemistry and Goodman Cancer Research Center, McGill University, Montréal, Québec, H3G 1Y6, Canada and School of Computer Science and McGill Centre for Bioinformatics, McGill University, Montréal, Québec, H3A 0E9, Canada
| | - Josée Dostie
- Department of Biochemistry and Goodman Cancer Research Center, McGill University, Montréal, Québec, H3G 1Y6, Canada and School of Computer Science and McGill Centre for Bioinformatics, McGill University, Montréal, Québec, H3A 0E9, Canada
| |
Collapse
|
10
|
Muskhelishvili G, Travers A. Integration of syntactic and semantic properties of the DNA code reveals chromosomes as thermodynamic machines converting energy into information. Cell Mol Life Sci 2013; 70:4555-67. [PMID: 23771629 PMCID: PMC11113758 DOI: 10.1007/s00018-013-1394-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Revised: 05/28/2013] [Accepted: 05/29/2013] [Indexed: 11/29/2022]
Abstract
Understanding genetic regulation is a problem of fundamental importance. Recent studies have made it increasingly evident that, whereas the cellular genetic regulation system embodies multiple disparate elements engaged in numerous interactions, the central issue is the genuine function of the DNA molecule as information carrier. Compelling evidence suggests that the DNA, in addition to the digital information of the linear genetic code (the semantics), encodes equally important continuous, or analog, information that specifies the structural dynamics and configuration (the syntax) of the polymer. These two DNA information types are intrinsically coupled in the primary sequence organisation, and this coupling is directly relevant to regulation of the genetic function. In this review, we emphasise the critical need of holistic integration of the DNA information as a prerequisite for understanding the organisational complexity of the genetic regulation system.
Collapse
Affiliation(s)
- Georgi Muskhelishvili
- School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, 28759, Bremen, Germany,
| | | |
Collapse
|
11
|
Papantonis A, Cook PR. Transcription factories: genome organization and gene regulation. Chem Rev 2013; 113:8683-705. [PMID: 23597155 DOI: 10.1021/cr300513p] [Citation(s) in RCA: 162] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Argyris Papantonis
- Sir William Dunn School of Pathology, University of Oxford , South Parks Road, Oxford OX1 3RE, United Kingdom
| | | |
Collapse
|
12
|
The 3D organization of the yeast genome correlates with co-expression and reflects functional relations between genes. PLoS One 2013; 8:e54699. [PMID: 23382942 PMCID: PMC3561378 DOI: 10.1371/journal.pone.0054699] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Accepted: 12/17/2012] [Indexed: 01/15/2023] Open
Abstract
The spatial organization of eukaryotic genomes is thought to play an important role in regulating gene expression. The recent advances in experimental methods including chromatin capture techniques, as well as the large amounts of accumulated gene expression data allow studying the relationship between spatial organization of the genome and co-expression of protein-coding genes. To analyse this genome-wide relationship at a single gene resolution, we combined the interchromosomal DNA contacts in the yeast genome measured by Duan et al. with a comprehensive collection of 1,496 gene expression datasets. We find significant enhancement of co-expression among genes with contact links. The co-expression is most prominent when two gene loci fall within 1,000 base pairs from the observed contact. We also demonstrate an enrichment of inter-chromosomal links between functionally related genes, which suggests that the non random nature of the genome organization serves to facilitate coordinated transcription in groups of genes.
Collapse
|
13
|
Janga SC. From specific to global analysis of posttranscriptional regulation in eukaryotes: posttranscriptional regulatory networks. Brief Funct Genomics 2012; 11:505-21. [PMID: 23124862 DOI: 10.1093/bfgp/els046] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Regulation of gene expression occurs at several levels in eukaryotic organisms and is a highly controlled process. Although RNAs have been traditionally viewed as passive molecules in the pathway from transcription to translation, there is mounting evidence that their metabolism is controlled by a class of proteins called RNA-binding proteins (RBPs), as well as a number of small RNAs. In this review, I provide an overview of the recent developments in our understanding of the repertoire of RBPs across diverse model systems, and discuss the computational and experimental approaches currently available for the construction of posttranscriptional networks governed by them. I also present an overview of the different roles played by RBPs in the cellular context, based on their cis-regulatory modules identified in the literature and discuss how their interplay can result in the dynamic, spatial and tissue-specific expression maps of RNAs. I finally present the concept of posttranscriptional network of RBPs and their cognate RNA targets and discuss their cross-talk with other important posttranscriptional regulatory molecules such as microRNAs s, resulting in diverse functional network motifs. I argue that with rapid developments in the genome-wide elucidation of posttranscriptional networks it would not only be possible to gain a deeper understanding of regulation at a level that has been under-appreciated in the past, but would also allow us to use the newly developed high-throughput approaches to interrogate the prevalence of these phenomena in different states, and thereby study their relevance to physiology and disease across organisms.
Collapse
Affiliation(s)
- Sarath Chandra Janga
- School of Informatics, Indiana University Purdue University, Indianapolis, Indiana, Center for Computational Biology and Bioinformatics, Indiana University School of Medicine, 719 Indiana Ave Ste 319, Walker Plaza Building, IN 46202, USA.
| |
Collapse
|
14
|
Akiyama Y, Kimura K, Yamada-Akiyama H, Kubota A, Takahara Y, Ueyama Y. Genomic characteristics of a diploid F(4) festulolium hybrid (Lolium multiflorum × Festuca arundinacea). Genome 2012; 55:599-603. [PMID: 22856536 DOI: 10.1139/g2012-048] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The grass festulolium, a hybrid between the genera Festuca and Lolium , has a variety of beneficial agronomic attributes derived from both parents. Compared with high-ploidy festulolium, diploid festulolium is well suited to stabilizing ploidy and for studying agronomic traits and genetic relationships. We sought to produce a diploid festulolium hybrid that was resistant to summer depression, by hybridizing diploid Lolium multiflorum Lam. and hexaploid Festuca arundinacea Schreb., which has a high tolerance to summer depression. We obtained seven diploid F(4) plants that were capable of surviving the extremely hot summer in Morioka, Japan, in 2010, which was 2.7 °C higher than the average summer temperature. The observed resistance to summer depression in these plants was likely due to heat stress tolerance. The genomic constitutions of these seven hybrids were analyzed by GISH, and the chromosomal characteristics of a single diploid F(4) was analyzed by FISH using rDNA probes. The results showed that although no Festuca-specific genome remained in any of the seven diploid F(4) plants, extensive chromosomal rearrangement was observed in one of them. Our findings suggested that hybridizing diploid L. multiflorum and hexaploid F. arundinacea may be useful for modifying chromosome architecture in the Lolium genome with potential applications in chromosome engineering.
Collapse
Affiliation(s)
- Yukio Akiyama
- Livestock and Forage Research Division, Tohoku Agricultural Research Center, National Agriculture and Food Research Organization, Akahira 4, Shimokuriyagawa, Morioka, Iwate 020-0198, Japan.
| | | | | | | | | | | |
Collapse
|
15
|
Sandhu KS. Did the modulation of expression noise shape the evolution of three dimensional genome organizations in eukaryotes? Nucleus 2012; 3:286-9. [PMID: 22572956 DOI: 10.4161/nucl.20263] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The pervasive role of distant chromatin interactions in transcriptional regulation is increasingly becoming evident. There is a possibility that the greater diversity in chromatin interactions of a genomic locus could contribute to stochastic variation in its gene expression. However, this issue has not been addressed. Here, I present a few lines of evidence, which suggest that the variation in trans chromatin interactions might occur at the cost of expression noise. Genomic regions with nucleosome depletion, abundant and rapid transcription and with essential gene clusters exhibit relatively fewer trans chromatin interactions in the nucleus. Moreover, loci with greater number of interactions tend to show higher expression noise. Based on these observations, I hypothesize that the three dimensional organization of eukaryotic genomes might have evolved under a selective pressure to minimize the expression noise of essential gene clusters in the nucleus.
Collapse
|
16
|
Ram PT, Mendelsohn J, Mills GB. Bioinformatics and systems biology. Mol Oncol 2012; 6:147-54. [PMID: 22377422 DOI: 10.1016/j.molonc.2012.01.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2011] [Accepted: 01/24/2012] [Indexed: 11/20/2022] Open
Abstract
Delivering personalized therapeutic options to cancer patients based on the genetic and molecular aberrations of the tumor offers great promise to improve the outcomes of cancer therapy. Significant progress in biotechnology has allowed the measurement of tens of thousands of "omic" data points across multiple levels (DNA, RNA protein, metabolomics) from a single tumor biopsy sample in a reasonable time frame for making clinical decisions. With this data in hand, the challenge from the bioinformatics and systems biology point of view is how does one convert data into information and knowledge that can improve the delivery of personalized therapy to the patient.
Collapse
Affiliation(s)
- Prahlad T Ram
- Department of Systems Biology, Institute for Personalized Cancer Therapy, The University of Texas, MD Anderson Cancer Center, Houston, TX 77054, USA.
| | | | | |
Collapse
|
17
|
Eshar S, Dahan-Pasternak N, Weiner A, Dzikowski R. High resolution 3D perspective of Plasmodium biology: advancing into a new era. Trends Parasitol 2011; 27:548-54. [DOI: 10.1016/j.pt.2011.08.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Revised: 08/01/2011] [Accepted: 08/03/2011] [Indexed: 11/30/2022]
|
18
|
Rustenholz C, Choulet F, Laugier C, Šafář J, Šimková H, Doležel J, Magni F, Scalabrin S, Cattonaro F, Vautrin S, Bellec A, Bergès H, Feuillet C, Paux E. A 3,000-loci transcription map of chromosome 3B unravels the structural and functional features of gene islands in hexaploid wheat. PLANT PHYSIOLOGY 2011; 157:1596-608. [PMID: 22034626 PMCID: PMC3327205 DOI: 10.1104/pp.111.183921] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
To improve our understanding of the organization and regulation of the wheat (Triticum aestivum) gene space, we established a transcription map of a wheat chromosome (3B) by hybridizing a newly developed wheat expression microarray with bacterial artificial chromosome pools from a new version of the 3B physical map as well as with cDNA probes derived from 15 RNA samples. Mapping data for almost 3,000 genes showed that the gene space spans the whole chromosome 3B with a 2-fold increase of gene density toward the telomeres due to an increase in the number of genes in islands. Comparative analyses with rice (Oryza sativa) and Brachypodium distachyon revealed that these gene islands are composed mainly of genes likely originating from interchromosomal gene duplications. Gene Ontology and expression profile analyses for the 3,000 genes located along the chromosome revealed that the gene islands are enriched significantly in genes sharing the same function or expression profile, thereby suggesting that genes in islands acquired shared regulation during evolution. Only a small fraction of these clusters of cofunctional and coexpressed genes was conserved with rice and B. distachyon, indicating a recent origin. Finally, genes with the same expression profiles in remote islands (coregulation islands) were identified suggesting long-distance regulation of gene expression along the chromosomes in wheat.
Collapse
MESH Headings
- Base Sequence
- Brachypodium/genetics
- Centromere/genetics
- Chromosomes, Artificial, Bacterial/genetics
- Chromosomes, Plant/genetics
- DNA, Intergenic/genetics
- DNA, Plant/chemistry
- DNA, Plant/genetics
- Evolution, Molecular
- Gene Duplication
- Gene Expression Profiling
- Gene Expression Regulation, Plant/genetics
- Genes, Plant/genetics
- Genome, Plant/genetics
- Genomic Islands/genetics
- Genomic Islands/physiology
- Molecular Sequence Data
- Multigene Family
- Oligonucleotide Array Sequence Analysis
- Oryza/genetics
- Physical Chromosome Mapping/methods
- Polyploidy
- Sequence Analysis, DNA
- Telomere/genetics
- Transcriptome
- Triticum/genetics
Collapse
|
19
|
Rousseau M, Fraser J, Ferraiuolo MA, Dostie J, Blanchette M. Three-dimensional modeling of chromatin structure from interaction frequency data using Markov chain Monte Carlo sampling. BMC Bioinformatics 2011; 12:414. [PMID: 22026390 PMCID: PMC3245522 DOI: 10.1186/1471-2105-12-414] [Citation(s) in RCA: 109] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2011] [Accepted: 10/25/2011] [Indexed: 12/22/2022] Open
Abstract
Background Long-range interactions between regulatory DNA elements such as enhancers, insulators and promoters play an important role in regulating transcription. As chromatin contacts have been found throughout the human genome and in different cell types, spatial transcriptional control is now viewed as a general mechanism of gene expression regulation. Chromosome Conformation Capture Carbon Copy (5C) and its variant Hi-C are techniques used to measure the interaction frequency (IF) between specific regions of the genome. Our goal is to use the IF data generated by these experiments to computationally model and analyze three-dimensional chromatin organization. Results We formulate a probabilistic model linking 5C/Hi-C data to physical distances and describe a Markov chain Monte Carlo (MCMC) approach called MCMC5C to generate a representative sample from the posterior distribution over structures from IF data. Structures produced from parallel MCMC runs on the same dataset demonstrate that our MCMC method mixes quickly and is able to sample from the posterior distribution of structures and find subclasses of structures. Structural properties (base looping, condensation, and local density) were defined and their distribution measured across the ensembles of structures generated. We applied these methods to a biological model of human myelomonocyte cellular differentiation and identified distinct chromatin conformation signatures (CCSs) corresponding to each of the cellular states. We also demonstrate the ability of our method to run on Hi-C data and produce a model of human chromosome 14 at 1Mb resolution that is consistent with previously observed structural properties as measured by 3D-FISH. Conclusions We believe that tools like MCMC5C are essential for the reliable analysis of data from the 3C-derived techniques such as 5C and Hi-C. By integrating complex, high-dimensional and noisy datasets into an easy to interpret ensemble of three-dimensional conformations, MCMC5C allows researchers to reliably interpret the result of their assay and contrast conformations under different conditions. Availability http://Dostielab.biochem.mcgill.ca
Collapse
Affiliation(s)
- Mathieu Rousseau
- McGill Centre for Bioinformatics, Bellini Building, Life Sciences Complex, 3649 Promenade Sir William Osler, Montréal, Québec, H3G 0B1, Canada
| | | | | | | | | |
Collapse
|
20
|
Weiner A, Dahan-Pasternak N, Shimoni E, Shinder V, von Huth P, Elbaum M, Dzikowski R. 3D nuclear architecture reveals coupled cell cycle dynamics of chromatin and nuclear pores in the malaria parasite Plasmodium falciparum. Cell Microbiol 2011; 13:967-77. [DOI: 10.1111/j.1462-5822.2011.01592.x] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
|
21
|
Abstract
Trypanosomes are a group of protozoan eukaryotes, many of which are major parasites of humans and livestock. The genomes of trypanosomes and their modes of gene expression differ in several important aspects from those of other eukaryotic model organisms. Protein-coding genes are organized in large directional gene clusters on a genome-wide scale, and their polycistronic transcription is not generally regulated at initiation. Transcripts from these polycistrons are processed by global trans-splicing of pre-mRNA. Furthermore, in African trypanosomes, some protein-coding genes are transcribed by a multifunctional RNA polymerase I from a specialized extranucleolar compartment. The primary DNA sequence of the trypanosome genomes and their cellular organization have usually been treated as separate entities. However, it is becoming increasingly clear that in order to understand how a genome functions in a living cell, we will need to unravel how the one-dimensional genomic sequence and its trans-acting factors are arranged in the three-dimensional space of the eukaryotic nucleus. Understanding this cell biology of the genome will be crucial if we are to elucidate the genetic control mechanisms of parasitism. Here, we integrate the concepts of nuclear architecture, deduced largely from studies of yeast and mammalian nuclei, with recent developments in our knowledge of the trypanosome genome, gene expression, and nuclear organization. We also compare this nuclear organization to those in other systems in order to shed light on the evolution of nuclear architecture in eukaryotes.
Collapse
|
22
|
Early Career Research Award Lecture. Structure, evolution and dynamics of transcriptional regulatory networks. Biochem Soc Trans 2011; 38:1155-78. [PMID: 20863280 DOI: 10.1042/bst0381155] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The availability of entire genome sequences and the wealth of literature on gene regulation have enabled researchers to model an organism's transcriptional regulation system in the form of a network. In such a network, TFs (transcription factors) and TGs (target genes) are represented as nodes and regulatory interactions between TFs and TGs are represented as directed links. In the present review, I address the following topics pertaining to transcriptional regulatory networks. (i) Structure and organization: first, I introduce the concept of networks and discuss our understanding of the structure and organization of transcriptional networks. (ii) Evolution: I then describe the different mechanisms and forces that influence network evolution and shape network structure. (iii) Dynamics: I discuss studies that have integrated information on dynamics such as mRNA abundance or half-life, with data on transcriptional network in order to elucidate general principles of regulatory network dynamics. In particular, I discuss how cell-to-cell variability in the expression level of TFs could permit differential utilization of the same underlying network by distinct members of a genetically identical cell population. Finally, I conclude by discussing open questions for future research and highlighting the implications for evolution, development, disease and applications such as genetic engineering.
Collapse
|
23
|
Construction, Structure and Dynamics of Post-Transcriptional Regulatory Network Directed by RNA-Binding Proteins. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 722:103-17. [DOI: 10.1007/978-1-4614-0332-6_7] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
|
24
|
Abstract
Understanding the evolutionary origin of the nucleus and its compartmentalized architecture provides a huge but, as expected, greatly rewarding challenge in the post-genomic era. We start this chapter with a survey of current hypotheses on the evolutionary origin of the cell nucleus. Thereafter, we provide an overview of evolutionarily conserved features of chromatin organization and arrangements, as well as topographical aspects of DNA replication and transcription, followed by a brief introduction of current models of nuclear architecture. In addition to features which may possibly apply to all eukaryotes, the evolutionary plasticity of higher-order nuclear organization is reflected by cell-type- and species-specific features, by the ability of nuclear architecture to adapt to specific environmental demands, as well as by the impact of aberrant nuclear organization on senescence and human disease. We conclude this chapter with a reflection on the necessity of interdisciplinary research strategies to map epigenomes in space and time.
Collapse
|
25
|
Neighbourhood continuity is not required for correct testis gene expression in Drosophila. PLoS Biol 2010; 8:e1000552. [PMID: 21151342 PMCID: PMC2994658 DOI: 10.1371/journal.pbio.1000552] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2010] [Accepted: 10/20/2010] [Indexed: 01/26/2023] Open
Abstract
Disrupting the linear organization of testis gene expression neighborhoods in the Drosophila genome does not affect gene expression, suggesting that neighborhood organization is not primarily driven by gene expression requirements. It is now widely accepted that gene organisation in eukaryotic genomes is non-random and it is proposed that such organisation may be important for gene expression and genome evolution. In particular, the results of several large-scale gene expression analyses in a range of organisms from yeast to human indicate that sets of genes with similar tissue-specific or temporal expression profiles are clustered within the genome in gene expression neighbourhoods. While the existence of neighbourhoods is clearly established, the underlying reason for this facet of genome organisation is currently unclear and there is little experimental evidence that addresses the genomic requisites for neighbourhood organisation. We report the targeted disruption of three well-defined male-specific gene expression neighbourhoods in the Drosophila genome by the synthesis of precisely mapped chromosomal inversions. We compare gene expression in individuals carrying inverted chromosomes with their non-inverted but otherwise identical progenitors using whole-transcriptome microarray analysis, validating these data with specific quantitative real-time PCR assays. For each neighbourhood we generate and examine multiple inversions. We find no significant differences in the expression of genes that define each of the neighbourhoods. We further show that the inversions spatially separate both halves of a neighbourhood in the nucleus. Thus, models explaining neighbourhood organisation in terms of local sequence interactions, enhancer crosstalk, or short-range chromatin effects are unlikely to account for this facet of genome organisation. Our study challenges the notion that, at least in the case of the testis, expression neighbourhoods are a feature of eukaryotic genome organisation necessary for correct gene expression. The order of genes within eukaryotic genomes is not completely random. In all genomes characterised to date there are regions of the genome, known as gene expression neighbourhoods, which contain clusters of genes that are expressed together in a particular tissue or at a particular developmental stage. Comparative genomics indicates that at least some neighbourhoods have been conserved during evolution, suggesting that this facet of genome organisation may be functionally advantageous. While several models explaining the organisation of the genome into neighbourhoods have been proposed, the functional significance of neighbourhood organisation has not been experimentally tested. Here, we report experiments that disrupt defined testis gene expression neighbourhoods in the Drosophila genome. We generated chromosomal inversions with a breakpoint within a neighbourhood, defined as having genes co-expressed within the testis. Comparing gene expression in flies carrying inversions with their otherwise identical progenitors shows that maintaining the linear organisation of genes in a neighbourhood is not necessary for correct gene expression. We also show that it is not necessary for genes in a neighbourhood to be in close proximity in the nucleus for them to be co-expressed, since the inversions disrupt the spatial organisation of neighbourhood genes in the nucleus. Our experiments indicate that the current models used to account for the existence of gene expression neighbourhoods are unlikely to be sufficient.
Collapse
|
26
|
Grimaud C, Becker PB. Form and function of dosage-compensated chromosomes--a chicken-and-egg relationship. Bioessays 2010; 32:709-17. [PMID: 20658709 DOI: 10.1002/bies.201000029] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Does the three-dimensional (3D) conformation of interphase chromosomes merely reflect their function or does it actively contribute to gene regulation? The analysis of sex chromosomes that are subject to chromosome-wide dosage compensation processes promises new insight into this question. Chromosome conformations are dynamic and largely determined by association of distant chromosomal loci in the nuclear space or by their anchoring to the nuclear envelope, effectively generating chromatin loops. The type and extent of such interactions depend on chromatin-bound transcription regulators and therefore reflects function. Dosage compensation adjusts the overall transcription activity of X chromosomes to assure balanced expression in the two sexes. Initial analyses of mammalian and Drosophila X chromosomes have led to the hypothesis that their conformations may not only reflect their functional state but may in turn contribute to the coordination of chromosome-wide tuning of transcription.
Collapse
Affiliation(s)
- Charlotte Grimaud
- Adolf-Butenandt-Institute and Centre for Integrated Protein Science (CiPSM) Ludwig-Maximilians University, Munich, Germany
| | | |
Collapse
|
27
|
Skupsky R, Burnett JC, Foley JE, Schaffer DV, Arkin AP. HIV promoter integration site primarily modulates transcriptional burst size rather than frequency. PLoS Comput Biol 2010; 6:e1000952. [PMID: 20941390 PMCID: PMC2947985 DOI: 10.1371/journal.pcbi.1000952] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2010] [Accepted: 09/07/2010] [Indexed: 12/11/2022] Open
Abstract
Mammalian gene expression patterns, and their variability across populations of cells, are regulated by factors specific to each gene in concert with its surrounding cellular and genomic environment. Lentiviruses such as HIV integrate their genomes into semi-random genomic locations in the cells they infect, and the resulting viral gene expression provides a natural system to dissect the contributions of genomic environment to transcriptional regulation. Previously, we showed that expression heterogeneity and its modulation by specific host factors at HIV integration sites are key determinants of infected-cell fate and a possible source of latent infections. Here, we assess the integration context dependence of expression heterogeneity from diverse single integrations of a HIV-promoter/GFP-reporter cassette in Jurkat T-cells. Systematically fitting a stochastic model of gene expression to our data reveals an underlying transcriptional dynamic, by which multiple transcripts are produced during short, infrequent bursts, that quantitatively accounts for the wide, highly skewed protein expression distributions observed in each of our clonal cell populations. Interestingly, we find that the size of transcriptional bursts is the primary systematic covariate over integration sites, varying from a few to tens of transcripts across integration sites, and correlating well with mean expression. In contrast, burst frequencies are scattered about a typical value of several per cell-division time and demonstrate little correlation with the clonal means. This pattern of modulation generates consistently noisy distributions over the sampled integration positions, with large expression variability relative to the mean maintained even for the most productive integrations, and could contribute to specifying heterogeneous, integration-site-dependent viral production patterns in HIV-infected cells. Genomic environment thus emerges as a significant control parameter for gene expression variation that may contribute to structuring mammalian genomes, as well as be exploited for survival by integrating viruses.
Collapse
Affiliation(s)
- Ron Skupsky
- California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, California, United States of America
| | - John C. Burnett
- Department of Chemical Engineering, University of California, Berkeley, Berkeley, California, United States of America
- Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, California, United States of America
| | - Jonathan E. Foley
- UCB/UCSF Joint-Graduate-Group-in-Bioengineering, University of California, Berkeley, Berkeley, California, United States of America
| | - David V. Schaffer
- California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, California, United States of America
- Department of Chemical Engineering, University of California, Berkeley, Berkeley, California, United States of America
- Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, California, United States of America
- Department of Bioengineering, University of California, Berkeley, Berkeley, California, United States of America
| | - Adam P. Arkin
- California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, California, United States of America
- Department of Bioengineering, University of California, Berkeley, Berkeley, California, United States of America
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
| |
Collapse
|
28
|
Crutchley JL, Wang XQD, Ferraiuolo MA, Dostie J. Chromatin conformation signatures: ideal human disease biomarkers? Biomark Med 2010; 4:611-29. [PMID: 20701449 DOI: 10.2217/bmm.10.68] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Human health is related to information stored in our genetic code, which is highly variable even amongst healthy individuals. Gene expression is orchestrated by numerous control elements that may be located anywhere in the genome, and can regulate distal genes by physically interacting with them. These DNA contacts can be mapped with the chromosome conformation capture and related technologies. Several studies now demonstrate that gene expression patterns are associated with specific chromatin structures, and may therefore correlate with chromatin conformation signatures. Here, we present an overview of genome organization and its relationship with gene expression. We also summarize how chromatin conformation signatures can be identified and discuss why they might represent ideal biomarkers of human disease in such genetically diverse populations.
Collapse
Affiliation(s)
- Jennifer L Crutchley
- Department of Biochemistry, McGill University, 3655 Promenade Sir-William-Osler, Room 814, Montréal, Québec, Canada
| | - Xue Qing David Wang
- Department of Biochemistry, McGill University, 3655 Promenade Sir-William-Osler, Room 814, Montréal, Québec, Canada
| | - Maria A Ferraiuolo
- Department of Biochemistry, McGill University, 3655 Promenade Sir-William-Osler, Room 814, Montréal, Québec, Canada
| | | |
Collapse
|
29
|
Genomic neighbourhood and the regulation of gene expression. Curr Opin Cell Biol 2010; 22:326-33. [DOI: 10.1016/j.ceb.2010.04.004] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2010] [Revised: 04/12/2010] [Accepted: 04/13/2010] [Indexed: 12/31/2022]
|
30
|
Takahashi H, Hotta K, Takagi C, Ueno N, Satoh N, Shoguchi E. Regulation of notochord-specific expression of Ci-Bra downstream genes in Ciona intestinalis embryos. Zoolog Sci 2010; 27:110-8. [PMID: 20141416 DOI: 10.2108/zsj.27.110] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Brachyury, a T-box transcription factor, is expressed in ascidian embryos exclusively in primordial notochord cells and plays a pivotal role in differentiation of notochord cells. Previously, we identified approximately 450 genes downstream of Ciona intestinalis Brachyury (Ci-Bra), and characterized the expression profiles of 45 of these in differentiating notochord cells. In this study, we looked for cisregulatory sequences in minimal enhancers of 20 Ci-Bra downstream genes by electroporating region within approximately 3 kb upstream of each gene fused with lacZ. Eight of the 20 reporters were expressed in notochord cells. The minimal enchancer for each of these eight genes was narrowed to a region approximately 0.5-1.0-kb long. We also explored the genome-wide and coordinate regulation of 43 Ci-Bra-downstream genes. When we determined their chromosomal localization, it became evident that they are not clustered in a given region of the genome, but rather distributed evenly over 13 of the 14 pairs of chromosomes, suggesting that gene clustering does not contribute to coordinate control of the Ci-Bra downstream gene expression. Our results might provide Insights Into the molecular mechanisms underlying notochord formation in chordates.
Collapse
Affiliation(s)
- Hiroki Takahashi
- Department of Developmental Biology, National Institute for Basic Biology, Okazaki, Aichi 445-8585, Japan.
| | | | | | | | | | | |
Collapse
|
31
|
Chen WH, de Meaux J, Lercher MJ. Co-expression of neighbouring genes in Arabidopsis: separating chromatin effects from direct interactions. BMC Genomics 2010; 11:178. [PMID: 20233415 PMCID: PMC2851598 DOI: 10.1186/1471-2164-11-178] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2009] [Accepted: 03/16/2010] [Indexed: 11/24/2022] Open
Abstract
Background In all eukaryotic species examined, genes that are chromosomal neighbours are more similar in their expression than random gene pairs. Currently, it is still unclear how much of this local co-expression is caused by direct transcriptional interactions, and how much is due to shared chromatin environments. Results We analysed neighbouring genes in Arabidopsis thaliana. At large intergenic distances (>400 bp), divergently and convergently transcribed gene pairs show very similar levels of co-expression, mediated most likely by shared chromatin environments. At gene distances below 400 bp, co-expression is strongly enhanced only for divergently transcribed gene pairs, indicating bi-directional transcription from a single promoter. Conversely, co-expression is suppressed for short convergently or uni-directionally transcribed pairs. This suppression points to transcriptional interference concentrated at the 3' end, e.g., in the context of transcription termination. Conclusions Classifying linked gene pairs by their orientation, we are able to partially tease apart the different levels of regional expression modulation. (i) Regional chromatin characteristics modulate the accessibility for regulation and transcription, regardless of gene orientation; the strength of this chromatin effect can be assessed from divergently or convergently transcribed distant neighbours. (ii) Shared promoter regions up to 400 bp in length enhance the co-expression of close bi-directional neighbours. (iii) Transcriptional interference of close neighbours is concentrated at the 3' ends of genes, and reduces co-expression on average by 40%.
Collapse
Affiliation(s)
- Wei-Hua Chen
- Bioinformatics, Heinrich-Heine University Duesseldorf, 40225, Germany
| | | | | |
Collapse
|
32
|
Lavoie H, Hogues H, Mallick J, Sellam A, Nantel A, Whiteway M. Evolutionary tinkering with conserved components of a transcriptional regulatory network. PLoS Biol 2010; 8:e1000329. [PMID: 20231876 PMCID: PMC2834713 DOI: 10.1371/journal.pbio.1000329] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2009] [Accepted: 02/03/2010] [Indexed: 12/14/2022] Open
Abstract
A surprising level of evolutionary plasticity is revealed by analysis of differences between related yeasts in the mechanisms regulating the essential cellular process of ribosomal gene expression. Gene expression variation between species is a major contributor to phenotypic diversity, yet the underlying flexibility of transcriptional regulatory networks remains largely unexplored. Transcription of the ribosomal regulon is a critical task for all cells; in S. cerevisiae the transcription factors Rap1, Fhl1, Ifh1, and Hmo1 form a multi-subunit complex that controls ribosomal gene expression, while in C. albicans this regulation is under the control of Tbf1 and Cbf1. Here, we analyzed, using full-genome transcription factor mapping, the roles, in both S. cerevisiae and C. albicans, of each orthologous component of this complete set of regulators. We observe dramatic changes in the binding profiles of the generalist regulators Cbf1, Hmo1, Rap1, and Tbf1, while the Fhl1-Ifh1 dimer is the only component involved in ribosomal regulation in both fungi: it activates ribosomal protein genes and rDNA expression in a Tbf1-dependent manner in C. albicans and a Rap1-dependent manner in S. cerevisiae. We show that the transcriptional regulatory network governing the ribosomal expression program of two related yeast species has been massively reshaped in cis and trans. Changes occurred in transcription factor wiring with cellular functions, movements in transcription factor hierarchies, DNA-binding specificity, and regulatory complexes assembly to promote global changes in the architecture of the fungal transcriptional regulatory network. Conserved metabolic machineries direct energy production and investment in most life forms. However, variation in the transcriptional regulation of the genes that encode this machinery has been observed and shown to contribute to phenotypic differences between species. Here, we show that the regulatory circuits governing the expression of central metabolic components (in this case the ribosomes) in different yeast species have an unexpected level of evolutionary plasticity. Most transcription factors involved in the regulation of expression of ribosomal genes have in fact been reused in new ways during the evolutionary time separating S. cerevisiae and C. albicans to generate global changes in transcriptional network structures and new ribosomal regulatory complexes.
Collapse
Affiliation(s)
- Hugo Lavoie
- Biotechnology Research Institute, National Research Council, Montreal, Quebec, Canada
- Department of Biology, McGill University, Montreal, Quebec, Canada
| | - Hervé Hogues
- Biotechnology Research Institute, National Research Council, Montreal, Quebec, Canada
| | - Jaideep Mallick
- Biotechnology Research Institute, National Research Council, Montreal, Quebec, Canada
| | - Adnane Sellam
- Biotechnology Research Institute, National Research Council, Montreal, Quebec, Canada
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, Canada
| | - André Nantel
- Biotechnology Research Institute, National Research Council, Montreal, Quebec, Canada
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, Canada
| | - Malcolm Whiteway
- Biotechnology Research Institute, National Research Council, Montreal, Quebec, Canada
- Department of Biology, McGill University, Montreal, Quebec, Canada
- * E-mail:
| |
Collapse
|
33
|
Abstract
The "Chromosome Conformation Capture" (3C) and 3C-related technologies are used to measure physical contacts between DNA segments at high resolution in vivo. 3C studies indicate that genomes are likely organized into dynamic networks of physical contacts between genes and regulatory DNA elements. These interactions are mediated by proteins and are important for the regulation of genes. For these reasons, mapping physical connectivity networks with 3C-related approaches will be essential to fully understand how genes are regulated. The 3C-Carbon Copy (5C) technology can be used to measure chromatin contacts genome-scale within (cis) or between (trans) chromosomes. Although unquestionably powerful, this approach can be challenging to implement without proper understanding and application of publicly available bioinformatics tools. This chapter explains how 5C studies are performed and describes stepwise how to use currently available bioinformatics tools for experimental design, data analysis, and interpretation.
Collapse
Affiliation(s)
- James Fraser
- Department of Biochemistry, Goodman Cancer Research Center, McGill University, Montréal, QC, Canada.
| | | | | | | |
Collapse
|
34
|
Kheradmand Kia S, Solaimani Kartalaei P, Farahbakhshian E, Pourfarzad F, von Lindern M, Verrijzer CP. EZH2-dependent chromatin looping controls INK4a and INK4b, but not ARF, during human progenitor cell differentiation and cellular senescence. Epigenetics Chromatin 2009; 2:16. [PMID: 19954516 PMCID: PMC3225837 DOI: 10.1186/1756-8935-2-16] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2009] [Accepted: 12/02/2009] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The INK4b-ARF-INK4a tumour suppressor locus controls the balance between progenitor cell renewal and cancer. In this study, we investigated how higher-order chromatin structure modulates differential expression of the human INK4b-ARF-INK4a locus during progenitor cell differentiation, cellular ageing and senescence of cancer cells. RESULTS We found that INK4b and INK4a, but not ARF, are upregulated following the differentiation of haematopoietic progenitor cells, in ageing fibroblasts and in senescing malignant rhabdoid tumour cells. To investigate the underlying molecular mechanism we analysed binding of polycomb group (PcG) repressive complexes (PRCs) and the spatial organization of the INK4b-ARF-INK4a locus. In agreement with differential derepression, PcG protein binding across the locus is discontinuous. As we described earlier, PcG repressors bind the INK4a promoter, but not ARF. Here, we identified a second peak of PcG binding that is located approximately 3 kb upstream of the INK4b promoter. During progenitor cell differentiation and ageing, PcG silencer EZH2 attenuates, causing loss of PRC binding and transcriptional activation of INK4b and INK4a. The expression pattern of the locus is reflected by its organization in space. In the repressed state, the PRC-binding regions are in close proximity, while the intervening chromatin harbouring ARF loops out. Down regulation of EZH2 causes release of the approximately 35 kb repressive chromatin loop and induction of both INK4a and INK4b, whereas ARF expression remains unaltered. CONCLUSION PcG silencers bind and coordinately regulate INK4b and INK4a, but not ARF, during a variety of physiological processes. Developmentally regulated EZH2 levels are one of the factors that can determine the higher order chromatin structure and expression pattern of the INK4b-ARF-INK4a locus, coupling human progenitor cell differentiation to proliferation control. Our results revealed a chromatin looping mechanism of long-range control and argue against models involving homogeneous spreading of PcG silencers across the INK4b-ARF-INK4a locus.
Collapse
Affiliation(s)
- Sima Kheradmand Kia
- Department of Biochemistry, Center for Biomedical Genetics, Erasmus University Medical Center, PO Box 1738, 3000 DR Rotterdam, The Netherlands.
| | | | | | | | | | | |
Collapse
|
35
|
Yanai I, Hunter CP. Comparison of diverse developmental transcriptomes reveals that coexpression of gene neighbors is not evolutionarily conserved. Genome Res 2009; 19:2214-20. [PMID: 19745112 DOI: 10.1101/gr.093815.109] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Genomic analyses have shown that adjacent genes are often coexpressed. However, it remains unclear whether the observed coexpression is a result of functional organization or a consequence of adjacent active chromatin or transcriptional read-through, which may be free of selective biases. Here, we compare temporal expression profiles of one-to-one orthologs in conserved or divergent genomic positions in two genetically distant nematode species-Caenorhabditis elegans and C. briggsae-that share a near-identical developmental program. We find, for all major patterns of temporal expression, a substantive amount of gene expression divergence. However, this divergence is not random: Genes that function in essential developmental processes show less divergence than genes whose functions are not required for viability. Coexpression of gene neighbors in either species is highly divergent in the other, in particular when the neighborhood is not conserved. Interestingly, essential genes appear to maintain their expression profiles despite changes in neighborhoods suggesting exposure to stronger selection. Our results suggest that a significant fraction of the coexpression observed among gene neighbors may be accounted for by neutral processes, and further that these may be distinguished by comparative gene expression analyses.
Collapse
Affiliation(s)
- Itai Yanai
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
| | | |
Collapse
|
36
|
De S, Teichmann SA, Babu MM. The impact of genomic neighborhood on the evolution of human and chimpanzee transcriptome. Genome Res 2009; 19:785-94. [PMID: 19233772 DOI: 10.1101/gr.086165.108] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Divergence of gene expression can result in phenotypic variation, which contributes to the evolution of new species. Although the influence of trans- and cis-regulatory mutations is well known, the genome-wide impact of changes in genomic neighborhood of genes on expression divergence between species remains largely unexplored. Here, we compare the neighborhood of orthologous genes (within a window of 2 MB) in human and chimpanzee with the expression levels of their transcripts from several equivalent tissues and demonstrate that genes with altered neighborhood are more likely to undergo expression divergence than genes with conserved neighborhood. We observe the same trend when expression divergence data were analyzed from six different brain parts that are equivalent between human and chimpanzee. Additionally, we find enrichment for genes with altered neighborhood to be expressed in a tissue-specific manner in the human brain. These results suggest that expression divergence induced by this mechanism could have contributed to the phenotypic differences between human and chimpanzee. We propose that, in addition to other molecular mechanisms, change in genomic neighborhood is an important factor that drives transcriptome evolution.
Collapse
|