Transcriptionally Active Chromatin—Lessons Learned from the Chicken Erythrocyte Chromatin Fractionation

The chicken erythrocyte model system has been valuable to the study of chromatin structure and function, specifically for genes involved in oxygen transport and the innate immune response. Several seminal features of transcriptionally active chromatin were discovered in this system. Davie and colleagues capitalized on the unique features of the chicken erythrocyte to separate and isolate transcriptionally active chromatin and silenced chromatin, using a powerful native fractionation procedure. Histone modifications, histone variants, atypical nucleosomes (U-shaped nucleosomes) and other chromatin structural features (open chromatin) were identified in these studies. More recently, the transcriptionally active chromosomal domains in the chicken erythrocyte genome were mapped by combining this chromatin fractionation method with next-generation DNA and RNA sequencing. The landscape of histone modifications relative to chromatin structural features in the chicken erythrocyte genome was reported in detail, including the first ever mapping of histone H4 asymmetrically dimethylated at Arg 3 (H4R3me2a) and histone H3 symmetrically dimethylated at Arg 2 (H3R2me2s), which are products of protein arginine methyltransferases (PRMTs) 1 and 5, respectively. PRMT1 is important in the establishment and maintenance of chicken erythrocyte transcriptionally active chromatin.

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A haploid affair: core histone transitions during spermatogenesis

Biochemistry and Cell Biology ◽

10.1139/o03-045 ◽

2003 ◽

Vol 81 (3) ◽

pp. 131-140 ◽

Cited By ~ 52

Author(s):

John D Lewis ◽

D Wade Abbott ◽

Juan Ausió

Keyword(s):

Histone Modifications ◽

Chromatin Structure ◽

Critical Role ◽

Diploid Cell ◽

Histone Variants ◽

Histone H4 ◽

Dna Compaction ◽

Dynamic Composition ◽

Shed Light

The process of meiosis reduces a diploid cell to four haploid gametes and is accompanied by extensive recombination. Thus, the dynamics of chromatin during meiosis are significantly different than in mitotic cells. As spermatogenesis progresses, there is a widespread reorganization of the haploid genome followed by extensive DNA compaction. It has become increasingly clear that the dynamic composition of chromatin plays a critical role in the activities of enzymes and processes that act upon it. Therefore, an analysis of the role of histone variants and modifications in these processes may shed light upon the mechanisms involved and the control of chromatin structure in general. Histone variants such as histone H3.3, H2AX, and macroH2A appear to play key roles in the various stages of spermiogenesis, in addition to the specifically modulated acetylation of histone H4 (acH4), ubiquitination of histones H2A and H2B (uH2A, uH2B), and phosphorylation of histone H3 (H3p). This review will examine recent discoveries concerning the role of histone modifications and variants during meiosis and spermatogenesis.Key words: histone variants, histone modifications, chromatin structure, meiosis.

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Inferring time series chromatin states for promoter-enhancer pairs based on Hi-C data

BMC Genomics ◽

10.1186/s12864-021-07373-z ◽

2021 ◽

Vol 22 (1) ◽

Author(s):

Henriette Miko ◽

Yunjiang Qiu ◽

Bjoern Gaertner ◽

Maike Sander ◽

Uwe Ohler

Keyword(s):

Time Series ◽

Histone Modifications ◽

Gene Activation ◽

Expectation Maximization Algorithm ◽

Chromatin State ◽

Open Chromatin ◽

Multiple Time ◽

Enhancer Activity ◽

Chromatin States ◽

Multiple Time Points

Abstract Background Co-localized combinations of histone modifications (“chromatin states”) have been shown to correlate with promoter and enhancer activity. Changes in chromatin states over multiple time points (“chromatin state trajectories”) have previously been analyzed at promoter and enhancers separately. With the advent of time series Hi-C data it is now possible to connect promoters and enhancers and to analyze chromatin state trajectories at promoter-enhancer pairs. Results We present TimelessFlex, a framework for investigating chromatin state trajectories at promoters and enhancers and at promoter-enhancer pairs based on Hi-C information. TimelessFlex extends our previous approach Timeless, a Bayesian network for clustering multiple histone modification data sets at promoter and enhancer feature regions. We utilize time series ATAC-seq data measuring open chromatin to define promoters and enhancer candidates. We developed an expectation-maximization algorithm to assign promoters and enhancers to each other based on Hi-C interactions and jointly cluster their feature regions into paired chromatin state trajectories. We find jointly clustered promoter-enhancer pairs showing the same activation patterns on both sides but with a stronger trend at the enhancer side. While the promoter side remains accessible across the time series, the enhancer side becomes dynamically more open towards the gene activation time point. Promoter cluster patterns show strong correlations with gene expression signals, whereas Hi-C signals get only slightly stronger towards activation. The code of the framework is available at https://github.com/henriettemiko/TimelessFlex. Conclusions TimelessFlex clusters time series histone modifications at promoter-enhancer pairs based on Hi-C and it can identify distinct chromatin states at promoter and enhancer feature regions and their changes over time.

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Identification and Characterization of the Genes Encoding the Core Histones and Histone Variants of Neurospora crassa

Genetics ◽

10.1093/genetics/160.3.961 ◽

2002 ◽

Vol 160 (3) ◽

pp. 961-973 ◽

Cited By ~ 1

Author(s):

Shan M Hays ◽

Johanna Swanson ◽

Eric U Selker

Keyword(s):

Neurospora Crassa ◽

Histone Variants ◽

Null Alleles ◽

Histone Genes ◽

Histone H4 ◽

Coding Regions ◽

The Core ◽

Genomic Arrangement ◽

Genes Encoding ◽

Core Histones

Abstract We have identified and characterized the complete complement of genes encoding the core histones of Neurospora crassa. In addition to the previously identified pair of genes that encode histones H3 and H4 (hH3 and hH4-1), we identified a second histone H4 gene (hH4-2), a divergently transcribed pair of genes that encode H2A and H2B (hH2A and hH2B), a homolog of the F/Z family of H2A variants (hH2Az), a homolog of the H3 variant CSE4 from Saccharomyces cerevisiae (hH3v), and a highly diverged H4 variant (hH4v) not described in other species. The hH4-1 and hH4-2 genes, which are 96% identical in their coding regions and encode identical proteins, were inactivated independently. Strains with inactivating mutations in either gene were phenotypically wild type, in terms of growth rates and fertility, but the double mutants were inviable. As expected, we were unable to isolate null alleles of hH2A, hH2B, or hH3. The genomic arrangement of the histone and histone variant genes was determined. hH2Az and the hH3-hH4-1 gene pair are on LG IIR, with hH2Az centromere-proximal to hH3-hH4-1 and hH3 centromere-proximal to hH4-1. hH3v and hH4-2 are on LG IIIR with hH3v centromere-proximal to hH4-2. hH4v is on LG IVR and the hH2A-hH2B pair is located immediately right of the LG VII centromere, with hH2A centromere-proximal to hH2B. Except for the centromere-distal gene in the pairs, all of the histone genes are transcribed toward the centromere. Phylogenetic analysis of the N. crassa histone genes places them in the Euascomycota lineage. In contrast to the general case in eukaryotes, histone genes in euascomycetes are few in number and contain introns. This may be a reflection of the evolution of the RIP (repeat-induced point mutation) and MIP (methylation induced premeiotically) processes that detect sizable duplications and silence associated genes.

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Maintenance of Open Chromatin and Selective Genomic Occupancy at the Cell Cycle-Regulated Histone H4 Promoter during Differentiation of HL-60 Promyelocytic Leukemia Cells

Molecular and Cellular Biology ◽

10.1128/mcb.23.4.1460-1469.2003 ◽

2003 ◽

Vol 23 (4) ◽

pp. 1460-1469 ◽

Cited By ~ 19

Author(s):

Hayk Hovhannisyan ◽

Brian Cho ◽

Partha Mitra ◽

Martin Montecino ◽

Gary S. Stein ◽

...

Keyword(s):

Cell Cycle ◽

Kinase Inhibitor ◽

Restriction Enzymes ◽

Dnase I ◽

Promyelocytic Leukemia ◽

Micrococcal Nuclease ◽

Leukemia Cells ◽

N Gene ◽

Open Chromatin ◽

Histone H4

ABSTRACT During the shutdown of proliferation and onset of differentiation of HL-60 promyelocytic leukemia cells, expression of the cell cycle-dependent histone genes is downregulated at the level of transcription. To address the mechanism by which this regulation occurs, we examined the chromatin structure of the histone H4/n (FO108, H4FN) gene locus. Micrococcal nuclease, DNase I, and restriction enzymes show similar cleavage sites and levels of sensitivity at the H4/n locus in both proliferating and differentiated HL-60 cells. In contrast, differentiation-related activation of the cyclin-dependent kinase inhibitor p21cip1/WAF1 gene is accompanied by increased nuclease hypersensitivity. Chromatin immunoprecipitation assays of the H4/n gene reveal that acetylated histones H3 and H4 are maintained at the same levels in proliferating and postproliferative cells. Thus, the chromatin of the H4/n locus remains in an open state even after transcription ceases. Using ligation-mediated PCR to visualize genomic DNase I footprints at single-nucleotide resolution, we find that protein occupancy at the site II cell cycle element is selectively diminished in differentiated cells while the site I element remains occupied. Decreased occupancy of site II is reflected by loss of the site II binding protein HiNF-P. We conclude that H4 gene transcription during differentiation is downregulated by modulating protein interaction at the site II cell cycle element and that retention of an open chromatin conformation may be associated with site I occupancy.

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Interdependence between histone marks and steps in Pol II transcription

10.21203/rs.3.rs-149042/v1 ◽

2021 ◽

Author(s):

Charles Danko ◽

Zhong Wang ◽

Alexandra Chivu ◽

Lauren Choate ◽

Edward Rice ◽

...

Keyword(s):

Machine Learning ◽

Histone Modifications ◽

Dnase I ◽

Open Chromatin ◽

Learning Tools ◽

Pol Ii ◽

Histone Marks ◽

Chromatin States ◽

Hypersensitive Sites

Abstract The role of histone modifications in transcription remains incompletely understood. Here we used experimental perturbations combined with sensitive machine learning tools that infer the distribution of histone marks using maps of nascent transcription. Transcription predicted the variation in active histone marks and complex chromatin states, like bivalent promoters, down to single-nucleosome resolution and at an accuracy that rivaled the correspondence between independent ChIP-seq experiments. Blocking transcription rapidly removed two punctate marks, H3K4me3 and H3K27ac, from chromatin indicating that transcription is required for active histone modifications. Transcription was also required for maintenance of H3K27me3 consistent with a role for RNA in recruiting PRC2. A subset of DNase-I hypersensitive sites were refractory to prediction, precluding models where transcription initiates pervasively at any open chromatin. Our results, in combination with past literature, support a model in which active histone modifications serve a supportive, rather than a regulatory, role in transcription.

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Structural and biochemical analyses of monoubiquitinated human histones H2B and H4

Open Biology ◽

10.1098/rsob.160090 ◽

2016 ◽

Vol 6 (6) ◽

pp. 160090 ◽

Cited By ~ 23

Author(s):

Shinichi Machida ◽

Satoshi Sekine ◽

Yuuki Nishiyama ◽

Naoki Horikoshi ◽

Hitoshi Kurumizaka

Keyword(s):

Histone H4 ◽

Core Particle ◽

Post Translational Modification ◽

Nucleosome Core Particle ◽

Active Chromatin ◽

Histone H2b ◽

Nucleosome Core ◽

Nucleosome Structure ◽

Biochemical Analyses ◽

Nucleosome Stability

Monoubiquitination is a major histone post-translational modification. In humans, the histone H2B K120 and histone H4 K31 residues are monoubiquitinated and may form transcriptionally active chromatin. In this study, we reconstituted nucleosomes containing H2B monoubiquitinated at position 120 (H2Bub 120 ) and/or H4 monoubiquitinated at position 31 (H4ub 31 ). We found that the H2Bub 120 and H4ub 31 monoubiquitinations differently affect nucleosome stability: the H2Bub 120 monoubiquitination enhances the H2A–H2B association with the nucleosome, while the H4ub 31 monoubiquitination decreases the H3–H4 stability in the nucleosome, when compared with the unmodified nucleosome. The H2Bub 120 and H4ub 31 monoubiquitinations both antagonize the Mg 2+ -dependent compaction of a poly-nucleosome, suggesting that these monoubiquitinations maintain more relaxed conformations of chromatin. In the crystal structure, the H2Bub 120 and H4ub 31 monoubiquitinations do not change the structure of the nucleosome core particle and the ubiquitin molecules were flexibly disordered in the H2Bub 120 /H4ub 31 nucleosome structure. These results revealed the differences and similarities of the H2Bub 120 and H4ub 31 monoubiquitinations at the mono- and poly-nucleosome levels and provide novel information to clarify the roles of monoubiquitination in chromatin.

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Chromatin organization in the homogeneously staining regions of a methotrexate-resistant mouse cell line: interspersion of inactive and active chromatin domains distinguished by acetylation of histone H4

Journal of Cell Science ◽

10.1242/jcs.109.9.2221 ◽

1996 ◽

Vol 109 (9) ◽

pp. 2221-2228 ◽

Cited By ~ 2

Author(s):

L. Nicol ◽

P. Jeppesen

Keyword(s):

Cell Line ◽

Dna Sequences ◽

Satellite Dna ◽

Mouse Cell ◽

Histone H4 ◽

Active Chromatin ◽

Chromatin Domains ◽

Resistant Mouse ◽

Major Satellite ◽

Drosophila Heterochromatin

We have analyzed the organization of the homogeneously staining regions (HSRs) in chromosomes from a methotrexate-resistant mouse melanoma cell line. Fluorescence in situ hybridization techniques were used to localize satellite DNA sequences and the amplified copies of the dihydrofolate reductase (DHFR) gene that confer drug-resistance, in combination with immunofluorescence using antibody probes to differentiate chromatin structure. We show that the major DNA species contained in the HSRs is mouse major satellite, confirming previous reports, and that this is interspersed with DHFR DNA in an alternating tandem array that can be resolved at the cytological level. Mouse minor satellite DNA, which is normally located at centromeres, is also distributed along the HSRs, but does not appear to interfere with centromere function. The blocks of major satellite DNA are coincident with chromatin domains that are labelled by an autoantibody that recognizes a mammalian homologue of Drosophila heterochromatin-associated protein 1, shown previously to be confined to centric heterochromatin in mouse. An antiserum that specifically recognizes acetylated histone H4, a marker for active chromatin, fails to bind to the satellite DNA domains, but labels the intervening segments containing DHFR DNA. We can find no evidence for the spreading of the inactive chromatin domains into adjacent active chromatin, even after extended passaging of cells in the absence of methotrexate selection.

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Aging, cellular senescence and cancer: epigenetic alterations and nuclear remodeling

Epigenetics, Nuclear Organization & Gene Function ◽

10.1093/oso/9780198831204.003.0021 ◽

2019 ◽

pp. 238-253

Author(s):

John C. Lucchesi

Keyword(s):

Histone Modifications ◽

Cellular Senescence ◽

Aging Process ◽

Nuclear Architecture ◽

Gene Mutations ◽

Histone Variants ◽

Premature Aging ◽

Model Organisms ◽

Premature Aging Syndromes ◽

Nuclear Remodeling

Epigenetic modifications correlated with aging and oncogenesis are changes in the pattern of DNA methylation and of histone modifications, and changes in the level of histone variants (H3.3, macroH2A, H2A.Z) and gene mutations. The sirtuins are a set of highly conserved protein deacetylases of particular significance to the aging process. Many cancer types are found to carry mutations in chromatin-modifying genes such as those encoding methyl or acetyl transferases, affecting the histone modifications of promoters and enhancers. The aging process and oncogenesis present a number of changes in the nuclear architecture. Mutations in the lamina-coding genes lead to premature aging syndromes. Mutations in remodeling complexes are found in different cancers. Modifications that affect the architectural protein binding sites at topologically associating domain (TAD) borders can cause the merging of neighboring TADs. The levels of short non-coding RNAs (sncRNAs) are altered in model organisms and are associated with cancer. Changes in the position of chromosome territories often occur in tumor cells. Nevertheless, cellular senescence, due mostly to the absence of telomerase, represents a mechanism of tumor suppression.

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