This research was originally published in Mol Cell Proteomics. Soldi M. and Bonaldi T. The Proteomic Investigation of Chromatin Functional Domains Reveals Novel Synergisms among Distinct Heterochromatin Components MCP. 2013; 12: 64-80. &#169; the American Society for Biochemistry and Molecular Biology. We thank Roberta Noberini (Italian Institute of Technology and IEO, Italy) for critical reading of the manuscript. TB work is supported by grants from the Giovanni Armenise-Harvard Foundation Career Development Program, the Italian Association for Cancer Research and the Italian Ministry of Health. MS work was supported by a FIRC fellowship.

<ol>
	<li>Kornberg, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chromatin+structure:+a+repeating+unit+of+histones+and+DNA.">Chromatin structure: a repeating unit of histones and DNA.</a> Science. 184, 868-871 (1974).</li><li>Luger, K., Mader, A. W., Richmond, R. K., Sargent, D. F., Richmond, T. 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No conflicts of interest declared.

We have recently described ChroP, a quantitative strategy for the large-scale characterization of the protein components of chromatin. ChroP combines two complementary approaches used in the epigenetic field, ChIP and MS, profiting from their strengths and overcoming their respective limitations. ChIP coupled to deep sequencing (ChIP-Seq) allows the genome-wide mapping of histone modifications at the resolution of few nucleosomes35. Although advantageous for their sensitivity, antibody-based assays are limited...

Chromatin is a highly dynamic nucleoprotein complex that is involved as primary template for all DNA-mediated processes. The nucleosome is the basic repeated unit of chromatin and consists of a proteinaceous octameric core containing two molecules of each canonical histone H2A, H2B, H3 and H4, around which 147 bp of DNA are wrapped1,2. All core histones are structured as a globular domain and a flexible N-terminal &#8220;tail&#8221; that protrudes outside the nucleosome. One of the major mechanisms for regulating chromatin structure and dynamics is based on covalent post-translational modifications (PTMs), which mainly occur on the N-termini of histones3,4. Histone modifications can function either by altering the higher order chromatin structure, by changing contacts between histones-DNA or between nucleosomes, and thus controlling the accessibility of DNA-binding proteins (cis mechanisms), or by acting as docking sites for regulatory proteins, either as single units, or embedded in multimeric complexes. Such regulating proteins can exert their function in different ways: by modulating directly gene expression (i.e. TAF proteins), or by altering the nucleosome positioning (i.e. chromatin remodeling complexes) or by modifying other histone residues (i.e. proteins with methyl-transferase or acetyl-transferase activity) (trans mechanisms)5. The observation that distinct PTM patterns cluster at specific chromatin loci led to the elaboration of the hypothesis that different modifications at distinct sites may synergize to generate a molecular code mediating the functional state of the underlying DNA. The &#34;histone code hypothesis&#34; has gained large consensus in the years but its experimental verification has been held back by technical limitations6,7.
Mass spectrometry (MS)-based proteomics has emerged as a powerful tool to map histone modification patterns and to characterize chromatin-binding proteins8. MS detects a modification as a specific &#916;mass between the experimental and theoretical mass of a peptide. At the level of individual histones, MS provides an unbiased and comprehensive method to map PTMs, allowing the detection of new modifications and revealing interplays among them9-14.
In recent years, a number of strategies have been developed to dissect the proteomic composition of chromatin, including the characterization of intact mitotic chromosomes15, the identification of soluble hPTM-binding proteins16-18 and the isolation and analysis of specific chromatin regions (i.e. telomeres)19,20. However, the investigation of the locus-specific synergies between histone PTMs, variants, and chromatin-associated proteins is still incomplete. Here, we describe a new approach, named ChroP (Chromatin Proteomics)21, that we have developed to efficiently characterize functionally distinct chromatin domains. This approach adapts chromatin immunoprecipitation (ChIP), a well-established protocol used in epigenetic research, for the efficient MS-based proteomic analysis of the enriched sample. We have developed two different protocols, depending on the type of chromatin used as input and the question addressed by MS; in particular: 1) ChIP of unfixed native chromatin digested with MNase is employed to purify mono-nucleosomes and to dissect the co-associating hPTMs (N-ChroP); 2) ChIP of crosslinked chromatin fragmented by sonication is used in combination with a SILAC-based interactomics strategy to characterize all co-enriching chromatin binding proteins (X-ChroP). We illustrate here the combination of N- and X-ChroP for enriching and studying heterochromatin, using H3K9me3 as bait for the immunoprecipitation steps. The use of ChroP can be extended to study either distinct regions on chromatin, or changes in the chromatin composition within the same region during the transition to a different functional state, thus paving the way to various applications in epigenetics.

<table><tbody><tr><td>DMEM&amp;nbsp;</td><td>Lonza</td><td>BE12-614F</td><td></td></tr><tr><td>FBS</td><td>Invitrogen</td><td>10270-106</td><td></td></tr><tr><td>SILAC DMEM</td><td>M-Medical</td><td>FA30E15086</td><td></td></tr><tr><td>Dialyzed FBS</td><td>Invitrogen</td><td>26400-044</td><td></td></tr><tr><td>Lysine 0 (12C6 14N2 L-lysine)</td><td>Sigma Aldrich</td><td>L8662</td><td></td></tr><tr><td>Arginine 0 (12C6 14N4 L-arginine)</td><td>Sigma Aldrich</td><td>A6969</td><td></td></tr><tr><td>Lysine 8 (13C6 15N2 L-lysine)</td><td>Sigma Aldrich</td><td>68041</td><td></td></tr><tr><td>Arginine 10 (13C6 15N4 L-arginine)</td><td>Sigma Aldrich</td><td>608033</td><td></td></tr><tr><td>Micrococcal Nuclease</td><td>Roche</td><td>10 107 921 001</td><td></td></tr><tr><td>Complete, EDTA-free Protease Inhibitor Cocktail Tablets</td><td>Roche</td><td>04 693 132 001</td><td></td></tr><tr><td>Spectra/Por 3 dialysis tubing, 3.5K MWCO, 18mm flat width, 50 foot length</td><td>Spectrumlabs</td><td>132720</td><td></td></tr><tr><td>QIAquick PCR purification kit</td><td>QIAGEN</td><td>28104</td><td></td></tr><tr><td>Anti-Histone H3 tri-methylated K9-ChIP grade</td><td>Abcam</td><td>ab8898</td><td></td></tr><tr><td>Histone H3 peptide tri-methyl K9&amp;nbsp;</td><td>Abcam</td><td>ab1773</td><td></td></tr><tr><td>Dynabeads Protein G</td><td>Invitrogen</td><td>100.04D</td><td></td></tr><tr><td>NuPAGE Novex 4-12%&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp; Bis-Tris Gel&amp;nbsp;</td><td>Invitrogen</td><td>NP0335BOX</td><td></td></tr><tr><td>Colloidal Blue Staining Kit</td><td>Invitrogen</td><td>LC6025</td><td></td></tr><tr><td>LDS Sample Buffer</td><td>Invitrogen</td><td>NP0007</td><td></td></tr><tr><td>Formaldheyde</td><td>Sigma Aldrich</td><td>F8775</td><td></td></tr><tr><td>Aceti anhydride-d6</td><td>Sigma Aldrich</td><td>175641-1G</td><td></td></tr><tr><td colspan="4">[header]</td></tr><tr><td>Formic Acid</td><td>Sigma Aldrich</td><td>94318-50ML-F</td><td></td></tr><tr><td>Iodoacetamide &amp;ge;99% (HPLC), crystalline</td><td>Sigma Aldrich</td><td>I6125</td><td></td></tr><tr><td>DL-Dithiothreitol</td><td>Sigma Aldrich</td><td>43815</td><td></td></tr><tr><td>Sequencing Grade Modified Trypsin, Frozen 100 &amp;mu;g (5 &amp;times; 20 &amp;mu;g)</td><td>Promega</td><td>V5113</td><td></td></tr><tr><td>Nanospray OD 360&amp;mu;m x ID 75&amp;mu;m, tips ID 8 &amp;mu;m uncoated Pk 5</td><td>Microcolumn Srl</td><td>FS360-75-8-N-5-C15</td><td></td></tr><tr><td>ReproSil-Pur 120 C18-AQ, 3 &amp;micro;m&amp;nbsp;&amp;nbsp; 15% C</td><td>Dr. Maisch GmbH</td><td>r13.aq.</td><td></td></tr><tr><td>Carbon extraction disk, 47 mm</td><td>Agilent Technologies</td><td>12145040</td><td></td></tr><tr><td>Cation extraction disk</td><td>Agilent Technologies</td><td>66889-U</td><td></td></tr></tbody></table>

the chrop approach combines chip and mass spectrometry to dissect locus-specific proteomic landscapes of chromatin

Chromatin is a highly dynamic nucleoprotein complex made of DNA and proteins that controls various DNA-dependent processes. Chromatin structure and function at specific regions is regulated by the local enrichment of histone post-translational modifications (hPTMs) and variants, chromatin-binding proteins, including transcription factors, and DNA methylation. The proteomic characterization of chromatin composition at distinct functional regions has been so far hampered by the lack of efficient protocols to enrich such domains at the appropriate purity and amount for the subsequent in-depth analysis by Mass Spectrometry (MS). We describe here a newly designed chromatin proteomics strategy, named ChroP (Chromatin Proteomics), whereby a preparative chromatin immunoprecipitation is used to isolate distinct chromatin regions whose features, in terms of hPTMs, variants and co-associated non-histonic proteins, are analyzed by MS. We illustrate here the setting up of ChroP for the enrichment and analysis of transcriptionally silent heterochromatic regions, marked by the presence of tri-methylation of lysine 9 on histone H3. The results achieved demonstrate the potential of ChroP in thoroughly characterizing the heterochromatin proteome and prove it as a powerful analytical strategy for understanding how the distinct protein determinants of chromatin interact and synergize to establish locus-specific structural and functional configurations.

Chromatin immunoprecipitation is a powerful technique used to profile the localization of a protein or a histone modification along the genome. In a proteomics equivalent, ChIP is followed by MS-based proteomics to identify qualitatively and quantitatively the hPTMs, histone variants and chromatin-binding proteins that are immunoprecipitated together with the modification or protein of interest, used as &#8220;bait&#8221;. In the N-ChroP approach, outlined in Figure 1A, native ChIP, in which chromatin is...

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The ChroP Approach Combines ChIP and Mass Spectrometry to Dissect Locus-specific Proteomic Landscapes of Chromatin

By combining native and crosslinking chromatin immunoprecipitation with high-resolution Mass Spectrometry, ChroP approach enables to dissect the composite proteomic architecture of histone modifications, variants and non-histonic proteins synergizing at functionally distinct chromatin domains.

Chromatin is a highly dynamic nucleoprotein complex made of DNA and proteins that controls various DNA-dependent processes. Chromatin structure and ...

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Research

JoVE Journal

Biology

18.1K Views.  European Institute of Oncology. By combining native and crosslinking chromatin immunoprecipitation with high-resolution Mass Spectrometry, ChroP approach enables to dissect the composite proteomic architecture of histone modifications, variants and non-histonic proteins synergizing at functionally distinct chromatin domains.

Video: The ChroP Approach Combines ChIP and Mass Spectrometry to Dissect Locus-specific Proteomic Landscapes of Chromatin

An Integrated Platform for Genome-wide Mapping of Chromatin States Using High-throughput ChIP-sequencing in Tumor Tissues

Histone modifications constitute a major component of the epigenome and play important regulatory roles in determining the transcriptional status of associated loci. In addition, the presence of specific modifications has been used to determine the position and identity non-coding functional elements such as enhancers. In recent years, chromatin immunoprecipitation followed by next generation sequencing (ChIP-seq) has become a powerful tool in determining the genome-wide profiles of individual histone modifications. However, it has become increasingly clear that the combinatorial patterns of chromatin modifications, referred to as Chromatin States, determine the identity and nature of the associated genomic locus. Therefore, workflows consisting of robust high-throughput (HT) methodologies for profiling a number of histone modification marks, as well as computational analyses pipelines capable of handling myriads of ChIP-Seq profiling datasets, are needed for comprehensive determination of epigenomic states in large number of samples. The HT-ChIP-Seq workflow presented here consists of two modules: 1) an experimental protocol for profiling several histone modifications from small amounts of tumor samples and cell lines in a 96-well format; and 2) a computational data analysis pipeline that combines existing tools to compute both individual mark occupancy and combinatorial chromatin state patterns. Together, these two modules facilitate easy processing of hundreds of ChIP-Seq samples in a fast and efficient manner. The workflow presented here is used to derive chromatin state patterns from 6 histone mark profiles in melanoma tumors and cell lines. Overall, we present a comprehensive ChIP-seq workflow that can be applied to dozens of human tumor samples and cancer cell lines to determine epigenomic aberrations in various malignancies.

Here, we describe an optimized high-throughput ChIP-sequencing protocol and computational analyses pipeline for the determination of genome-wide chromatin state patterns from frozen tumor tissues and cell lines.

Histone modifications constitute a major component of the epigenome and play important regulatory roles in determining the transcriptional status of ...

Cancer Research

Adaptation of Hybridization Capture of Chromatin-associated Proteins for Proteomics to Mammalian Cells

The hybridization capture of chromatin-associated proteins for proteomics (HyCCAPP) technology was initially developed to uncover novel DNA-protein interactions in yeast. It allows analysis of a target region of interest without the need for prior knowledge about likely proteins bound to the target region. This, in theory, allows HyCCAPP to be used to analyze any genomic region of interest, and it provides sufficient flexibility to work in different cell systems. This method is not meant to study binding sites of known transcription factors, a task better suited for Chromatin Immunoprecipitation (ChIP) and ChIP-like methods. The strength of HyCCAPP lies in its ability to explore DNA regions for which there is limited or no knowledge about the proteins bound to it. It can also be a convenient method to avoid biases (present in ChIP-like methods) introduced by protein-based chromatin enrichment using antibodies. Potentially, HyCCAPP can be a powerful tool to uncover truly novel DNA-protein interactions. To date, the technology has been predominantly applied to yeast cells or to high copy repeat sequences in mammalian cells. In order to become the powerful tool we envision, HyCCAPP approaches need to be optimized to efficiently capture single-copy loci in mammalian cells. Here, we present our adaptation of the initial yeast HyCCAPP capture protocol to human cell lines, and show that single-copy chromatin regions can be efficiently isolated with this modified protocol.

This is a method to identify novel DNA-interacting proteins at specific target loci, relying on sequence-specific capture of crosslinked chromatin for subsequent proteomic analyses. No prior knowledge about potential binding proteins, nor cell modifications are required. Initially developed for yeast, the technology has now been adapted for mammalian cells.

The hybridization capture of chromatin-associated proteins for proteomics (HyCCAPP) technology was initially developed to uncover novel DNA-protein ...

Genetics

Quantitative Analysis of Chromatin Proteomes in Disease

In the nucleus reside the proteomes whose functions are most intimately linked with gene regulation. Adult mammalian cardiomyocyte nuclei are unique due to the high percentage of binucleated cells,1 the predominantly heterochromatic state of the DNA, and the non-dividing nature of the cardiomyocyte which renders adult nuclei in a permanent state of interphase.2 Transcriptional regulation during development and disease have been well studied in this organ,3-5 but what remains relatively unexplored is the role played by the nuclear proteins responsible for DNA packaging and expression, and how these proteins control changes in transcriptional programs that occur during disease.6 In the developed world, heart disease is the number one cause of mortality for both men and women.7 Insight on how nuclear proteins cooperate to regulate the progression of this disease is critical for advancing the current treatment options.
Mass spectrometry is the ideal tool for addressing these questions as it allows for an unbiased annotation of the nuclear proteome and relative quantification for how the abundance of these proteins changes with disease. While there have been several proteomic studies for mammalian nuclear protein complexes,8-13 until recently14 there has been only one study examining the cardiac nuclear proteome, and it considered the entire nucleus, rather than exploring the proteome at the level of nuclear sub compartments.15 In large part, this shortage of work is due to the difficulty of isolating cardiac nuclei. Cardiac nuclei occur within a rigid and dense actin-myosin apparatus to which they are connected via multiple extensions from the endoplasmic reticulum, to the extent that myocyte contraction alters their overall shape.16 Additionally, cardiomyocytes are 40% mitochondria by volume17 which necessitates enrichment of the nucleus apart from the other organelles. Here we describe a protocol for cardiac nuclear enrichment and further fractionation into biologically-relevant compartments. Furthermore, we detail methods for label-free quantitative mass spectrometric dissection of these fractions-techniques amenable to in vivo experimentation in various animal models and organ systems where metabolic labeling is not feasible.

Advances in mass spectrometry have allowed the high throughput analysis of protein expression and modification in a host of tissues. Combined with subcellular fractionation and disease models, quantitative mass spectrometry and bioinformatics can reveal new properties in biological systems. The method described herein analyzes chromatin-associated proteins in the setting of heart disease and is readily applicable to other in vivo models of human disease.

In the nucleus reside the proteomes whose functions are most intimately linked with gene regulation. Adult mammalian cardiomyocyte nuclei are unique due ...

Medicine

Genome-wide Analysis using ChIP to Identify Isoform-specific Gene Targets

Recruitment of transcriptional and epigenetic factors to their targets is a key step in their regulation. Prominently featured in recruitment are the protein domains that bind to specific histone modifications. One such domain is the plant homeodomain (PHD), found in several chromatin-binding proteins. The epigenetic factor RBP2 has multiple PHD domains, however, they have different functions (Figure 4). In particular, the C-terminal PHD domain, found in a RBP2 oncogenic fusion in human leukemia, binds to trimethylated lysine 4 in histone H3 (H3K4me3)1. The transcript corresponding to the RBP2 isoform containing the C-terminal PHD accumulates during differentiation of promonocytic, lymphoma-derived, U937 cells into monocytes2. Consistent with both sets of data, genome-wide analysis showed that in differentiated U937 cells, the RBP2 protein gets localized to genomic regions highly enriched for H3K4me33. Localization of RBP2 to its targets correlates with a decrease in H3K4me3 due to RBP2 histone demethylase activity and a decrease in transcriptional activity. In contrast, two other PHDs of RBP2 are unable to bind H3K4me3. Notably, the C-terminal domain PHD of RBP2 is absent in the smaller RBP2 isoform4. It is conceivable that the small isoform of RBP2, which lacks interaction with H3K4me3, differs from the larger isoform in genomic location. The difference in genomic location of RBP2 isoforms may account for the observed diversity in RBP2 function. Specifically, RBP2 is a critical player in cellular differentiation mediated by the retinoblastoma protein (pRB). Consistent with these data, previous genome-wide analysis, without distinction between isoforms, identified two distinct groups of RBP2 target genes: 1) genes bound by RBP2 in a manner that is independent of differentiation; 2) genes bound by RBP2 in a differentiation-dependent manner.
To identify differences in localization between the isoforms we performed genome-wide location analysis by ChIP-Seq. Using antibodies that detect both RBP2 isoforms we have located all RBP2 targets. Additionally we have antibodies that only bind large, and not small RBP2 isoform (Figure 4). After identifying the large isoform targets, one can then subtract them from all RBP2 targets to reveal the targets of small isoform. These data show the contribution of chromatin-interacting domain in protein recruitment to its binding sites in the genome.

Here we are presenting a chromatin immunoprecipitation (ChIP) procedure for genome-wide location analysis of protein isoforms that differ in a histone-binding domain. We are applying it to ChIP-Seq analysis to identify the targets of the KDM5A/JARID1A/RBP2 histone demethylase.

Recruitment of transcriptional and epigenetic factors to their targets is a key step in their regulation. Prominently featured in recruitment are the ...

Histone Proteomic Analysis and Post-Translational Modification Characterization

Histone Modification Screening using Liquid Chromatography, Trapped Ion Mobility Spectrometry, and Time-Of-Flight Mass Spectrometry

Histone proteins are highly abundant and conserved among eukaryotes and play a large role in gene regulation as a result of structures known as posttranslational modifications (PTMs). Identifying the position and nature of each PTM or pattern of PTMs in reference to external or genetic factors allows this information to be statistically correlated with biological responses such as DNA transcription, replication, or repair. In the present work, a high-throughput analytical protocol for the detection of histone PTMs from biological samples is described. The use of complementary liquid chromatography, trapped ion mobility spectrometry, and time-of-flight mass spectrometry (LC-TIMS-ToF MS/MS) enables the separation and PTM assignment of the most biologically relevant modifications in a single analysis. The described approach takes advantage of recent developments in dependent data acquisition (DDA) using parallel accumulation in the mobility trap, followed by sequential fragmentation and collision-induced dissociation. Histone PTMs are confidently assigned based on their retention time, mobility, and fragmentation pattern.

Author Spotlight: Enhanced Histone PTM Isomer Identification Through LC-TIMS-ToF MS/MS and PASEF

An analytical workflow based on liquid chromatography, trapped ion mobility spectrometry, and time-of-flight mass spectrometry (LC-TIMS-ToF MS/MS) for high confidence and highly reproducible "bottom-up" analysis of histone modifications and identification based on principal parameters (retention time [RT], collision cross section [CCS], and accurate mass-to-charge [m/z] ratio).

Histone proteins are highly abundant and conserved among eukaryotes and play a large role in gene regulation as a result of structures known as ...

Chemistry

Isolation and Cultivation of Neural Progenitors Followed by Chromatin-Immunoprecipitation of Histone 3 Lysine 79 Dimethylation Mark

Brain development is a complex process, which is controlled in a temporo-spatial manner by gradients of morphogens and different transcriptional programs. Additionally, epigenetic chromatin modifications, like histone methylation, have an important role for establishing and maintaining specific cell fates within this process. The vast majority of histone methylation occurs on the flexible histone tail, which is accessible to histone modifiers, erasers, and histone reader proteins. In contrast, H3K79 methylation is located in the globular domain of histone 3 and is implicated in different developmental functions. H3K79 methylation is evolutionarily conserved and can be found in a wide range of species from Homo sapiens to Saccharomyces cerevisiae. The modification occurs in different cell populations within organisms, including neural progenitors. The location of H3K79 methylation in the globular domain of histone 3 makes it difficult to assess. Here, we present methods to isolate and culture cortical progenitor cells (CPCs) from embryonic cortical brain tissue (E11.5-E14.5) or cerebellar granular neuron progenitors (CGNPs) from postnatal tissue (P5-P7), and to efficiently immunoprecipitate H3K79me2 for quantitative PCR (qPCR) and genome-wide sequencing.

We present an effective and reproducible method to isolate and culture neural progenitor cells from embryonic and postnatal brain tissue for chromatin immunoprecipitation (ChIP) of histone 3 lysine 79 dimethylation (H3K79me2) - a histone mark located within the globular domain of histone 3.

Brain development is a complex process, which is controlled in a temporo-spatial manner by gradients of morphogens and different transcriptional programs. ...

Neuroscience

Generation of High Quality Chromatin Immunoprecipitation DNA Template for High-throughput Sequencing (ChIP-seq)

ChIP-sequencing (ChIP-seq) methods directly offer whole-genome coverage, where combining chromatin immunoprecipitation (ChIP) and massively parallel sequencing can be utilized to identify the repertoire of mammalian DNA sequences bound by transcription factors in vivo. "Next-generation" genome sequencing technologies provide 1-2 orders of magnitude increase in the amount of sequence that can be cost-effectively generated over older technologies thus allowing for ChIP-seq methods to directly provide whole-genome coverage for effective profiling of mammalian protein-DNA interactions.
For successful ChIP-seq approaches, one must generate high quality ChIP DNA template to obtain the best sequencing outcomes. The description is based around experience with the protein product of the gene most strongly implicated in the pathogenesis of type 2 diabetes, namely the transcription factor transcription factor 7-like 2 (TCF7L2). This factor has also been implicated in various cancers.
Outlined is how to generate high quality ChIP DNA template derived from the colorectal carcinoma cell line, HCT116, in order to build a high-resolution map through sequencing to determine the genes bound by TCF7L2, giving further insight in to its key role in the pathogenesis of complex traits.

Generation of High Quality Chromatin Immunoprecipitation DNA Template for High-throughput Sequencing ChIP-seq

The combination of chromatin immunoprecipitation and ultra-high-throughput sequencing (ChIP-seq) can identify and map protein-DNA interactions in a given tissue or cell line. Outlined is how to generate a high quality ChIP template for subsequent sequencing, using experience with the transcription factor TCF7L2 as an example.

ChIP-sequencing (ChIP-seq) methods directly  offer whole-genome coverage, where combining chromatin immunoprecipitation  (ChIP) and massively parallel ...

Isolation of Specific Genomic Regions and Identification of Associated Molecules by enChIP

The identification of molecules associated with specific genomic regions of interest is required to understand the mechanisms of regulation of the functions of these regions. To enable the non-biased identification of molecules interacting with a specific genomic region of interest, we recently developed the engineered DNA-binding molecule-mediated chromatin immunoprecipitation (enChIP) technique. Here, we describe how to use enChIP to isolate specific genomic regions and identify the associated proteins and RNAs. First, a genomic region of interest is tagged with a transcription activator-like (TAL) protein or a clustered regularly interspaced short palindromic repeats (CRISPR) complex consisting of a catalytically inactive form of Cas9 and a guide RNA. Subsequently, the chromatin is crosslinked and fragmented by sonication. The tagged locus is then immunoprecipitated and the crosslinking is reversed. Finally, the proteins or RNAs that are associated with the isolated chromatin are subjected to mass spectrometric or RNA sequencing analyses, respectively. This approach allows the successful identification of proteins and RNAs associated with a genomic region of interest.

The identification of molecules associated with specific genomic regions of interest is required to understand the mechanisms of regulation of the functions of these regions. This protocol describes procedures to perform engineered DNA-binding molecule-mediated chromatin imunoprecipitation (enChIP) for identification of proteins and RNAs associated with a specific genomic region.

The identification of molecules associated with specific genomic regions of interest is required to understand the mechanisms of regulation of the ...

A Semiautomated ChIP-Seq Procedure for Large-scale Epigenetic Studies

Chromatin immunoprecipitation followed by sequencing (ChIP-Seq) is a powerful and widely used approach to profile chromatin DNA associated with specific histone modifications, such as H3K27ac, to help identify cis-regulatory DNA elements. The manual process to complete a ChIP-Seq is labor intensive, technically challenging, and often requires large-cell numbers (&#62;100,000 cells). The method described here helps to overcome those challenges. A complete semiautomated, microscaled H3K27ac ChIP-Seq procedure including cell fixation, chromatin shearing, immunoprecipitation, and sequencing library preparation, for batch of 48 samples for cell number inputs less than 100,000 cells is described in detail. The semiautonomous platform reduces technical variability, improves signal-to-noise ratios, and drastically reduces labor. The system can thereby reduce costs by allowing for reduced reaction volumes, limiting the number of expensive reagents such as enzymes, magnetic beads, antibodies, and hands-on time required. These improvements to the ChIP-Seq method suit perfectly for large-scale epigenetic studies of clinical samples with limited cell numbers in a highly reproducible manner.

This paper describes a semiautomated, microscaled ChIP-Seq protocol of DNA regions associated with a specific histone modification (H3K27ac) using a ChIP liquid-handler platform, followed by library preparation using tagmentation. The procedure includes control assessment for quality and quantity purposes and can be adopted to other histone modifications or transcription factors.

Chromatin immunoprecipitation followed by sequencing (ChIP-Seq) is a powerful and widely used approach to profile chromatin DNA associated with specific ...

Single-Cell Factor Localization on Chromatin using Ultra-Low Input Cleavage Under Targets and Release using Nuclease

Determining the binding locations of a protein on chromatin is essential for understanding its function and potential regulatory targets. Chromatin Immunoprecipitation (ChIP) has been the gold standard for determining protein localization for over 30 years and is defined by the use of an antibody to pull out the protein of interest from sonicated or enzymatically digested chromatin. More recently, antibody tethering techniques have become popular for assessing protein localization on chromatin due to their increased sensitivity. Cleavage Under Targets &amp; Release Under Nuclease (CUT&amp;RUN) is the genome-wide derivative of Chromatin Immunocleavage (ChIC) and utilizes recombinant Protein A tethered to micrococcal nuclease (pA-MNase) to identify the IgG constant region of the antibody targeting a protein of interest, therefore enabling site-specific cleavage of the DNA flanking the protein of interest. CUT&amp;RUN can be used to profile histone modifications, transcription factors, and other chromatin-binding proteins such as nucleosome remodeling factors. Importantly, CUT&amp;RUN can be used to assess the localization of either euchromatic- or heterochromatic-associated proteins and histone modifications. For these reasons, CUT&amp;RUN is a powerful method for determining the binding profiles of a wide range of proteins. Recently, CUT&amp;RUN has been optimized for transcription factor profiling in low populations of cells and single cells and the optimized protocol has been termed ultra-low input CUT&amp;RUN (uliCUT&amp;RUN). Here, a detailed protocol is presented for single-cell factor profiling using uliCUT&amp;RUN in a manual 96-well format.

CUT&#38;RUN and its variants can be used to determine protein occupancy on chromatin. This protocol describes how to determine protein localization on chromatin using single-cell uliCUT&#38;RUN.

Determining the binding locations of a protein on chromatin is essential for understanding its function and potential regulatory targets. Chromatin ...