scholarly journals Free energy based high-resolution modeling of CTCF-mediated chromatin loops for human genome

2017 ◽  
Author(s):  
Wayne Dawson ◽  
Dariusz Plewczynski
Keyword(s):  
Free Energy ◽  
Rna Polymerase Ii ◽  
Human Genome ◽  
Interaction Analysis ◽  
Minimum Free Energy ◽  
Chromatin Interaction ◽  
Specific Method ◽  
Genomic Distance ◽  
Chromosome Conformation ◽  
Chromatin Loops

AbstractIn recent years, chromatin has been found to have considerable structural organization in the human genome with diverse parts of the chromatin interacting with each other to form what have been termed topologically associated domains (TADs). Chromatin interaction analysis by paired-end tag sequencing (ChIA-PET) is a recent protein-specific method that measures these chromatin interactions via specific interactions such as CTCF-cohesin binding proteins or RNA polymerase II interactions. Unlike high-throughput chromosome conformation capture (Hi-C), which measures unspecific binding (all against all), ChIA-PET measures specific protein-protein contact interactions; hence physical bonds that reflect binding free energies. In this work, a thermodynamic method for computing the stability and dynamics of chromatin loops is proposed. The CTCF-mediated interactions, as observed in ChIA-PET experiments for human B-lymphoblastoid cells, are evaluated in terms of a chain folding polymer model and the experimentally observed frequency of contacts within the chromatin regions. To estimate the optimal free energy and a Boltzmann distribution of suboptimal structures, the approach uses dynamic programming with methods to handle degeneracy and heuristics to compute parallel and antiparallel chain stems and pseudoknots. Moreover, multiple loops mediated by CTCF protein binding that connects together more than one chain into multimeric islands are simulated using the model. Based on the thermodynamic properties of those topological three-dimensional structures, we predict the correlation between the relative activity of chromatin loop and the Boltzmann probability, or the minimum free energy, depending also on its genomic length. The results show that segments of chromatin where the structures show a more stable minimum free energy (for a given genomic distance) tend to be inactive, whereas structures that have lower stability in the minimum free energy (with the same genomic distance) tend to be active.

scholarly journals Oscillating and stable genome topologies underlie hepatic physiological rhythms during the circadian cycle

2020 ◽  
Author(s):  
Jérôme Mermet ◽  
Jake Yeung ◽  
Félix Naef
Keyword(s):  
Rna Polymerase Ii ◽  
Clock Genes ◽  
Gene Promoter ◽  
Chromatin Interaction ◽  
Gene Promoters ◽  
Chromatin Modifications ◽  
Chromosome Conformation ◽  
Time Resolved ◽  
Liver Physiology ◽  
Stable Genome

AbstractThe circadian clock drives extensive temporal gene expression programs controlling daily changes in behavior and physiology. In mouse liver, transcription factors dynamics, chromatin modifications, and RNA Polymerase II (PolII) activity oscillate throughout the 24-hour (24h) day, regulating the rhythmic synthesis of thousands of transcripts. Also, 24h rhythms in gene promoter-enhancer chromatin looping accompany rhythmic mRNA synthesis. However, how chromatin organization impinges on temporal transcription and liver physiology remains unclear. Here, we applied time-resolved chromosome conformation capture (4C-seq) in livers of WT and arrhythmic Bmal1 knockout mice. In WT, we observed 24h oscillations in promoter-enhancer contact at multiple loci including the core-clock genes Period1, Period2 and Bmal1. In addition, we detected rhythmic PolII activity, chromatin modifications and transcription involving stable chromatin loops at gene promoters representing key liver function such as glucose and lipid metabolism and detoxification. Intriguingly, these contacts persisted in clock-impaired mice in which both PolII activity and chromatin marks no longer oscillated. Finally, we observed chromatin interaction hubs connecting neighbouring genes showing coherent transcription regulation across genotypes. Thus, both clock-controlled and clock-independent chromatin topology underlie rhythmic regulation of liver physiology.

scholarly journals Characteristic arrangement of nucleosomes is predictive of chromatin interactions at kilobase resolution

2016 ◽  
Author(s):  
Hui Zhang ◽  
Feifei Li ◽  
Yan Jia ◽  
Bingxiang Xu ◽  
Yiqun Zhang ◽  
...  
Keyword(s):  
Interaction Analysis ◽  
Low Cost ◽  
Genome Structure ◽  
Cell Types ◽  
Regulatory Elements ◽  
Chromosome Conformation Capture ◽  
Computational Method ◽  
Chromatin Interaction ◽  
Chromosome Conformation ◽  
Interaction Sites

AbstractHigh-throughput chromosome conformation capture technologies, such as Hi-C, have made it possible to survey 3D genome structure. However, the ability to obtain 3D profiles at kilobase resolution at low cost remains a major challenge. Therefore, we herein report a computational method to precisely identify chromatin interaction sites at kilobase resolution from MNase-seq data, termed chromatin interaction site detector (CISD), and a CISD-based chromatin loop predictor (CISD_loop) that predicts chromatin-chromatin interaction (CCI) from low-resolution Hi-C data. The methods are built on a hypothesis that CCIs result in a characteristic nucleosome arrangement pattern flanking the interaction sites. Accordingly, we show that the predictions of CISD and CISD_loop overlap closely with chromatin interaction analysis by paired-end tag sequencing (ChIA-PET) anchors and loops, respectively. Moreover, the methods trained in one cell type can be applied to other cell types with high accuracy. The validity of the methods was further supported by chromosome conformation capture (3C) experiments at 5kb resolution. Finally, we demonstrate that only modest amounts of MNase-seq and Hi-C data are sufficient to achieve ultrahigh resolution CCI map. The predictive power of CISD/CISD_loop supports the hypothesis that CCIs induce local nucleosome rearrangement and that the pattern may serve as probes for 3D dynamics of the genome. Thus, our method will facilitate precise and systematic investigations of the interactions between distal regulatory elements on a larger scale than hitherto have been possible.

scholarly journals Chromatin Interaction Analysis with Updated ChIA-PET Tool (V3)

Genes ◽  
2019 ◽  
Vol 10 (7) ◽  
pp. 554 ◽  
Author(s):  
Li ◽  
Sun ◽  
Chang ◽  
Cai ◽  
Hong ◽  
...  
Keyword(s):  
Rna Polymerase Ii ◽  
Target Genes ◽  
Sequence Data ◽  
Interaction Analysis ◽  
Regulatory Elements ◽  
Chromatin Interaction ◽  
Data Set ◽  
Chromatin Interactions ◽  
A Genome ◽  
Public Data

Understanding chromatin interactions is important because they create chromosome conformation and link the cis- and trans- regulatory elements to their target genes for transcriptional regulation. Chromatin Interaction Analysis with Paired-End Tag (ChIA-PET) sequencing is a genome-wide high-throughput technology that detects chromatin interactions associated with a specific protein of interest. We developed ChIA-PET Tool for ChIA-PET data analysis in 2010. Here, we present the updated version of ChIA-PET Tool (V3) as a computational package to process the next-generation sequence data generated from ChIA-PET experiments. It processes short-read and long-read ChIA-PET data with multithreading and generates statistics of results in an HTML file. In this paper, we provide a detailed demonstration of the design of ChIA-PET Tool V3 and how to install it and analyze RNA polymerase II (RNAPII) ChIA-PET data from human K562 cells with it. We compared our tool with existing tools, including ChiaSig, MICC, Mango and ChIA-PET2, by using the same public data set in the same computer. Most peaks detected by the ChIA-PET Tool V3 overlap with those of other tools. There is higher enrichment for significant chromatin interactions from ChIA-PET Tool V3 in aggregate peak analysis (APA) plots. The ChIA-PET Tool V3 is publicly available at GitHub.

scholarly journals Oscillating and stable genome topologies underlie hepatic physiological rhythms during the circadian cycle

PLoS Genetics ◽  
2021 ◽  
Vol 17 (2) ◽  
pp. e1009350
Author(s):  
Jérôme Mermet ◽  
Jake Yeung ◽  
Felix Naef
Keyword(s):  
Rna Polymerase Ii ◽  
Clock Genes ◽  
Gene Promoter ◽  
Chromatin Interaction ◽  
Gene Promoters ◽  
Chromatin Modifications ◽  
Chromosome Conformation ◽  
Time Resolved ◽  
Liver Physiology ◽  
Stable Genome

The circadian clock drives extensive temporal gene expression programs controlling daily changes in behavior and physiology. In mouse liver, transcription factors dynamics, chromatin modifications, and RNA Polymerase II (PolII) activity oscillate throughout the 24-hour (24h) day, regulating the rhythmic synthesis of thousands of transcripts. Also, 24h rhythms in gene promoter-enhancer chromatin looping accompany rhythmic mRNA synthesis. However, how chromatin organization impinges on temporal transcription and liver physiology remains unclear. Here, we applied time-resolved chromosome conformation capture (4C-seq) in livers of WT and arrhythmic Bmal1 knockout mice. In WT, we observed 24h oscillations in promoter-enhancer loops at multiple loci including the core-clock genes Period1, Period2 and Bmal1. In addition, we detected rhythmic PolII activity, chromatin modifications and transcription involving stable chromatin loops at clock-output gene promoters representing key liver function such as glucose metabolism and detoxification. Intriguingly, these contacts persisted in clock-impaired mice in which both PolII activity and chromatin marks no longer oscillated. Finally, we observed chromatin interaction hubs connecting neighbouring genes showing coherent transcription regulation across genotypes. Thus, both clock-controlled and clock-independent chromatin topology underlie rhythmic regulation of liver physiology.

A sequence-based deep learning approach to predict CTCF-mediated chromatin loop

2021 ◽  
Author(s):  
Hao Lv ◽  
Fu-Ying Dao ◽  
Hasan Zulfiqar ◽  
Wei Su ◽  
Hui Ding ◽  
...  
Keyword(s):  
Computational Models ◽  
Genomic Sequence ◽  
Three Dimensional ◽  
Scoring Function ◽  
Cell Types ◽  
Frequency Component ◽  
Chromatin Interaction ◽  
Chromosome Conformation ◽  
Chromatin Loops ◽  
3D Architecture

Abstract Three-dimensional (3D) architecture of the chromosomes is of crucial importance for transcription regulation and DNA replication. Various high-throughput chromosome conformation capture-based methods have revealed that CTCF-mediated chromatin loops are a major component of 3D architecture. However, CTCF-mediated chromatin loops are cell type specific, and most chromatin interaction capture techniques are time-consuming and labor-intensive, which restricts their usage on a very large number of cell types. Genomic sequence-based computational models are sophisticated enough to capture important features of chromatin architecture and help to identify chromatin loops. In this work, we develop Deep-loop, a convolutional neural network model, to integrate k-tuple nucleotide frequency component, nucleotide pair spectrum encoding, position conservation, position scoring function and natural vector features for the prediction of chromatin loops. By a series of examination based on cross-validation, Deep-loop shows excellent performance in the identification of the chromatin loops from different cell types. The source code of Deep-loop is freely available at the repository https://github.com/linDing-group/Deep-loop.

Minimum free energy coding for DNA storage

2021 ◽  
pp. 1-1
Author(s):  
Ben Cao ◽  
Xiaokang Zhang ◽  
Jieqiong Wu ◽  
Bin Wang ◽  
Qiang Zhang ◽  
...  
Keyword(s):  
Free Energy ◽  
Minimum Free Energy ◽  
Dna Storage ◽  
Energy Coding

scholarly journals How proteins open fusion pores: insights from molecular simulations

2020 ◽  
Author(s):  
H. Jelger Risselada ◽  
Helmut Grubmüller
Keyword(s):  
Free Energy ◽  
Fusion Proteins ◽  
Graphics Processing Units ◽  
Fusion Reaction ◽  
Molecular Simulations ◽  
Minimum Free Energy ◽  
Free Energy Calculations ◽  
Coarse Grained ◽  
Fusion Pore ◽  
Graphics Processing

AbstractFusion proteins can play a versatile and involved role during all stages of the fusion reaction. Their roles go far beyond forcing the opposing membranes into close proximity to drive stalk formation and fusion. Molecular simulations have played a central role in providing a molecular understanding of how fusion proteins actively overcome the free energy barriers of the fusion reaction up to the expansion of the fusion pore. Unexpectedly, molecular simulations have revealed a preference of the biological fusion reaction to proceed through asymmetric pathways resulting in the formation of, e.g., a stalk-hole complex, rim-pore, or vertex pore. Force-field based molecular simulations are now able to directly resolve the minimum free-energy path in protein-mediated fusion as well as quantifying the free energies of formed reaction intermediates. Ongoing developments in Graphics Processing Units (GPUs), free energy calculations, and coarse-grained force-fields will soon gain additional insights into the diverse roles of fusion proteins.

scholarly journals Magic number colloidal clusters as minimum free energy structures

2018 ◽  
Vol 9 (1) ◽  
Author(s):  
Junwei Wang ◽  
Chrameh Fru Mbah ◽  
Thomas Przybilla ◽  
Benjamin Apeleo Zubiri ◽  
Erdmann Spiecker ◽  
...  
Keyword(s):  
Free Energy ◽  
Magic Number ◽  
Minimum Free Energy ◽  
Colloidal Clusters

scholarly journals Rock climbing: A local-global algorithm to compute minimum energy and minimum free energy pathways

2017 ◽  
Vol 147 (15) ◽  
pp. 152718 ◽  
Author(s):  
Clark Templeton ◽  
Szu-Hua Chen ◽  
Arman Fathizadeh ◽  
Ron Elber
Keyword(s):  
Free Energy ◽  
Minimum Energy ◽  
Minimum Free Energy ◽  
Rock Climbing ◽  
Global Algorithm ◽  
Energy Pathways

scholarly journals String method solution of the gating pathways for a pentameric ligand-gated ion channel

2017 ◽  
Vol 114 (21) ◽  
pp. E4158-E4167 ◽  
Author(s):  
Bogdan Lev ◽  
Samuel Murail ◽  
Frédéric Poitevin ◽  
Brett A. Cromer ◽  
Marc Baaden ◽  
...  
Keyword(s):  
Free Energy ◽  
Conformational Changes ◽  
Transmembrane Domain ◽  
Minimum Free Energy ◽  
Agonist Binding ◽  
String Method ◽  
Transition Analysis ◽  
Subunit Interface ◽  
Ion Conducting ◽  
Allosteric Mechanisms

Pentameric ligand-gated ion channels control synaptic neurotransmission by converting chemical signals into electrical signals. Agonist binding leads to rapid signal transduction via an allosteric mechanism, where global protein conformational changes open a pore across the nerve cell membrane. We use all-atom molecular dynamics with a swarm-based string method to solve for the minimum free-energy gating pathways of the proton-activated bacterial GLIC channel. We describe stable wetted/open and dewetted/closed states, and uncover conformational changes in the agonist-binding extracellular domain, ion-conducting transmembrane domain, and gating interface that control communication between these domains. Transition analysis is used to compute free-energy surfaces that suggest allosteric pathways; stabilization with pH; and intermediates, including states that facilitate channel closing in the presence of an agonist. We describe a switching mechanism that senses proton binding by marked reorganization of subunit interface, altering the packing of β-sheets to induce changes that lead to asynchronous pore-lining M2 helix movements. These results provide molecular details of GLIC gating and insight into the allosteric mechanisms for the superfamily of pentameric ligand-gated channels.

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