Determinants of nucleosome positioning.
01 Mar 2013-Nature Structural & Molecular Biology (Nature Publishing Group)-Vol. 20, Iss: 3, pp 267-273
TL;DR: The dominant patterns of nucleosome positioning that have been observed are reviewed, the current understanding of their underlying determinants are summarized and their implications for gene expression are summarized.
Abstract: Nucleosome positioning is crucial for gene expression and other DNA-related processes. In this Review, the authors consider mechanisms by which the genomic pattern of nucleosome positioning is achieved and conclude that nucleosome positioning is determined by the combined effects of several factors including DNA sequence, DNA-binding proteins, nucleosome remodelers and the transcription machinery.
Citations
More filters
Journal Article•
TL;DR: In this article, a nucleosome-DNA interaction model was proposed to predict the genome-wide organization of nucleosomes, and it was shown that genomes encode an intrinsic nucleosomal organization and that this intrinsic organization can explain ∼50% of the in-vivo positions.
Abstract: Eukaryotic genomes are packaged into nucleosome particles that occlude the DNA from interacting with most DNA binding proteins. Nucleosomes have higher affinity for particular DNA sequences, reflecting the ability of the sequence to bend sharply, as required by the nucleosome structure. However, it is not known whether these sequence preferences have a significant influence on nucleosome position in vivo, and thus regulate the access of other proteins to DNA. Here we isolated nucleosome-bound sequences at high resolution from yeast and used these sequences in a new computational approach to construct and validate experimentally a nucleosome–DNA interaction model, and to predict the genome-wide organization of nucleosomes. Our results demonstrate that genomes encode an intrinsic nucleosome organization and that this intrinsic organization can explain ∼50% of the in vivo nucleosome positions. This nucleosome positioning code may facilitate specific chromosome functions including transcription factor binding, transcription initiation, and even remodelling of the nucleosomes themselves.
1,399 citations
TL;DR: DNA affinity purification sequencing (DAP-seq) is described, a high-throughput TF binding site discovery method that interrogates genomic DNA with in-vitro-expressed TFs and determined that >75% of Arabidopsis TFs surveyed were methylation sensitive, a property that strongly impacts the epicistrome landscape.
985 citations
Cites background from "Determinants of nucleosome position..."
...Although DAP-seq was carried out on naked gDNA, the phasing pattern of ARF5 binding in target gene promoters resembled in vivo nucleosome phasing patterns found in active eukaryotic gene promoters (+1, 1 nucleosome, etc., locations) (Struhl and Segal, 2013)....
[...]
..., locations) (Struhl and Segal, 2013)....
[...]
TL;DR: Macrophage plasticity, an essential component of chronic inflammation, and its involvement in diverse human diseases, most notably cancer, is discussed here as a paradigm.
Abstract: Macrophages are a diverse set of cells present in all body compartments. This diversity is imprinted by their ontogenetic origin (embryonal versus adult bone marrow-derived cells); the organ context; by their activation or deactivation by various signals in the contexts of microbial invasion, tissue damage, and metabolic derangement; and by polarization of adaptive T cell responses. Classic adaptive responses of macrophages include tolerance, priming, and a wide spectrum of activation states, including M1, M2, or M2-like. Moreover, macrophages can retain long-term imprinting of microbial encounters (trained innate immunity). Single-cell analysis of mononuclear phagocytes in health and disease has added a new dimension to our understanding of the diversity of macrophage differentiation and activation. Epigenetic landscapes, transcription factors, and microRNA networks underlie the adaptability of macrophages to different environmental cues. Macrophage plasticity, an essential component of chronic inflammation, and its involvement in diverse human diseases, most notably cancer, is discussed here as a paradigm.
681 citations
TL;DR: It is demonstrated that reconstituted chromatin undergoes histone tail-driven liquid-liquid phase separation (LLPS) in physiologic salt and when microinjected into cell nuclei, producing dense and dynamic droplets.
610 citations
TL;DR: This work combined quantitative super-resolution nanoscopy with computer simulations to visualize and count nucleosomes along the chromatin fiber in single nuclei and reveal how the Chromatin fiber is formed at nanoscale level and link chromatin Fiber architecture to stem cell state.
537 citations
Cites background or result from "Determinants of nucleosome position..."
...In addition, genome-wide analyses have revealed that nucleosomes are depleted at promoter and terminator regions and at many enhancers (Struhl and Segal, 2013)....
[...]
...Our result comes very close to the occupancy level measured in genome-wide studies (Jiang and Pugh, 2009; Struhl and Segal, 2013)....
[...]
References
More filters
TL;DR: This study enters into the particular topics of the relative quantification in real-time RT-PCR of a target gene transcript in comparison to a reference gene transcript and presents a new mathematical model that needs no calibration curve.
Abstract: Use of the real-time polymerase chain reaction (PCR) to amplify cDNA products reverse transcribed from mRNA is on the way to becoming a routine tool in molecular biology to study low abundance gene expression. Real-time PCR is easy to perform, provides the necessary accuracy and produces reliable as well as rapid quantification results. But accurate quantification of nucleic acids requires a reproducible methodology and an adequate mathematical model for data analysis. This study enters into the particular topics of the relative quantification in real-time RT–PCR of a target gene transcript in comparison to a reference gene transcript. Therefore, a new mathematical model is presented. The relative expression ratio is calculated only from the real-time PCR efficiencies and the crossing point deviation of an unknown sample versus a control. This model needs no calibration curve. Control levels were included in the model to standardise each reaction run with respect to RNA integrity, sample loading and inter-PCR variations. High accuracy and reproducibility (<2.5% variation) were reached in LightCycler PCR using the established mathematical model.
30,462 citations
TL;DR: In this paper, a set of highest affinity molecules were selected, cloned and sequenced, their affinities (free energies) for histone octamer in nucleosome reconstitution measured, and their ability to position nucleosomes in vitro assessed by native gel electrophoresis.
1,587 citations
TL;DR: The field is reviewed and how pioneer factors may enable cellular reprogramming is described, which can passively enhance transcription by reducing the number of additional factors that are needed to bind the DNA, culminating in activation.
Abstract: Transcription factors are adaptor molecules that detect regulatory sequences in the DNA and target the assembly of protein complexes that control gene expression. Yet much of the DNA in the eukaryotic cell is in nucleosomes and thereby occluded by histones, and can be further occluded by higher-order chromatin structures and repressor complexes. Indeed, genome-wide location analyses have revealed that, for all transcription factors tested, the vast majority of potential DNA-binding sites are unoccupied, demonstrating the inaccessibility of most of the nuclear DNA. This raises the question of how target sites at silent genes become bound de novo by transcription factors, thereby initiating regulatory events in chromatin. Binding cooperativity can be sufficient for many kinds of factors to simultaneously engage a target site in chromatin and activate gene expression. However, in cases in which the binding of a series of factors is sequential in time and thus not initially cooperative, special "pioneer transcription factors" can be the first to engage target sites in chromatin. Such initial binding can passively enhance transcription by reducing the number of additional factors that are needed to bind the DNA, culminating in activation. In addition, pioneer factor binding can actively open up the local chromatin and directly make it competent for other factors to bind. Passive and active roles for the pioneer factor FoxA occur in embryonic development, steroid hormone induction, and human cancers. Herein we review the field and describe how pioneer factors may enable cellular reprogramming.
1,452 citations
Journal Article•
TL;DR: In this article, a nucleosome-DNA interaction model was proposed to predict the genome-wide organization of nucleosomes, and it was shown that genomes encode an intrinsic nucleosomal organization and that this intrinsic organization can explain ∼50% of the in-vivo positions.
Abstract: Eukaryotic genomes are packaged into nucleosome particles that occlude the DNA from interacting with most DNA binding proteins. Nucleosomes have higher affinity for particular DNA sequences, reflecting the ability of the sequence to bend sharply, as required by the nucleosome structure. However, it is not known whether these sequence preferences have a significant influence on nucleosome position in vivo, and thus regulate the access of other proteins to DNA. Here we isolated nucleosome-bound sequences at high resolution from yeast and used these sequences in a new computational approach to construct and validate experimentally a nucleosome–DNA interaction model, and to predict the genome-wide organization of nucleosomes. Our results demonstrate that genomes encode an intrinsic nucleosome organization and that this intrinsic organization can explain ∼50% of the in vivo nucleosome positions. This nucleosome positioning code may facilitate specific chromosome functions including transcription factor binding, transcription initiation, and even remodelling of the nucleosomes themselves.
1,399 citations
TL;DR: This work isolated nucleosome-bound sequences at high resolution from yeast and used these sequences in a new computational approach to construct and validate experimentally a nucleosom–DNA interaction model, and to predict the genome-wide organization of nucleosomes.
Abstract: Eukaryotic genomes are packaged into nucleosome particles that occlude the DNA from interacting with most DNA binding proteins. Nucleosomes have higher affinity for particular DNA sequences, reflecting the ability of the sequence to bend sharply, as required by the nucleosome structure. However, it is not known whether these sequence preferences have a significant influence on nucleosome position in vivo, and thus regulate the access of other proteins to DNA. Here we isolated nucleosome-bound sequences at high resolution from yeast and used these sequences in a new computational approach to construct and validate experimentally a nucleosome–DNA interaction model, and to predict the genome-wide organization of nucleosomes. Our results demonstrate that genomes encode an intrinsic nucleosome organization and that this intrinsic organization can explain ∼50% of the in vivo nucleosome positions. This nucleosome positioning code may facilitate specific chromosome functions including transcription factor binding, transcription initiation, and even remodelling of the nucleosomes themselves. Eukaryotic genomes do not exist in vivo as naked DNA, but in complexes known as chromatin. Chromatin contains nucleosomes, short stretches of DNA tightly wrapped around a histone protein core, which exclude most DNA binding proteins and so act as repressors. A combined computational and experimental approach has been used to determine DNA sequence preferences of nucleosomes and to predict genome-wide nucleosome organization. The yeast genome encodes an intrinsic nucleosome organization that explains about half of the in vivo nucleosome positions. Highly conserved across eukaryotes, the code directs transcription factors to their binding sites and facilitates many other specific chromosome functions. An accompanying News and Views piece discusses the role of DNA sequence and other regulators in nucleosome positioning. The cover graphic represents a stretch of chromatin including several nucleosomes. A combined computational and experimental approach is used to determine the DNA sequence preferences of nucleosomes and predict genome-wide nucleosome organization. The yeast genome encodes an intrinsic nucleosome organization, which can explain about 50% of in vivo nucleosome positions.
1,376 citations