A.L. was supported by a Canadian Graduate Scholarship from the Canadian Institutes of Health Research. This work was supported by grants from Genome British Columbia and the Canadian Institutes of Health Research (CIHR-120589) &#160;as part of the Canadian Epigenetics, Environment and Health Research Consortium Initiative and by the Terry Fox Research Institute Program Project Grant #TFF-122869 to M.H. and a Terry Fox Research Institute New Investigator Award (Grant # 1039) to M.H.

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The authors declare that they have no competing financial interests.

Given the combinatorial nature of chromatin modification and nucleosome positioning in transcriptional regulation, a method that enables simultaneous measurements of these features is likely to provide new insights into epigenetic regulation. The ndChIP-seq protocol presented here is a native ChIP-seq protocol optimized to enable simultaneous interrogation of histone modification and nucleosome density in rare primary cells9,10. ndChIP-seq utilizes enzymatic digestion of chromatin that, when coupled to paired-end massively parallel sequencing and a Gaussian mixture distribution model, allows for the investigation histone modifications at single nucleosome level and the deconvolution of epigenomic profiles driven by heterogeneity within a population. Using this protocol, we have previously reported a unique distribution of immuno-precipitated fragment sizes, determined by paired-end read boundaries, associated with specific chromatin states defined by ChromHMM10,24.
The quality of a ndChIP-seq library depends on multiple factors, such as antibody specificity and sensitivity, optimal MNase digestion conditions, and quality of the chromatin. The specificity of the antibodies used is crucial in producing successful ndChIP-seq library. An ideal antibody shows high affinity against the epitope of interest with little cross reactivity with other epitopes. It is equally important to choose magnetic beads with the highest affinity for the antibody of choice.
MNase digestion is a critical and time- and concentration-sensitive reaction in this protocol. Therefore, when processing multiple samples, it is important that each reaction is incubated for an equivalent amount of time (see step 2.2). The quality of the chromatin is another factor that significantly effects the outcome of ndChIP-seq. Fragmented chromatin leads to a sub-optimal MNase digestion profile and results in libraries with a low signal to noise ratio. Primary samples with low cell viability or degraded chromatin, such as formalin-fixed paraffin-embedded (FFPE) tissue are not recommended for this protocol.
The addition of a PIC during chromatin extraction reduces undesired (i.e., random) chromatin fragmentation and preserves integrity of histone tails. As such, PIC needs to be added to lysis buffer and immunoprecipitation buffer just prior to use. While selecting cells via flow cytometry, select for viable cells and ensure cells are sorted at a low flow rate to increase the accuracy of the cell number estimate and viability of cells. Avoid sorting cells directly into lysis buffer. The sheath buffer will dilute the lysis buffer and prevents effective permeabilization of the cell membrane to MNase. Depending on a type of cells or organism, titration of MNase may be required to obtain optimal digestion.
ndChIP-seq on mammalian cells requires a minimum sequencing depth of 50 million paired-reads (25 million fragments) for narrow marks and 100 million paired-reads (50 million fragments) for broad marks and input. The Gaussian mixture distribution algorithm will not perform optimally on libraries that have been sequenced to a depth significantly below this recommendation. ndChIP-seq will not classify promoters with little separation between the weighted distribution value for mono- and di-nucleosome fragment lengths into mono- or di-nucleosome dominated promoters. Therefore, these promoters must be removed in the subsequent analysis. Biological replicates can be generated to increase confidence in predicted distributions and identify technical variability in the MNase digestion and library construction.
Unlike previous iterations of native ChIP-seq protocols, ndChIP-seq provides the means to investigate combinatorial effect of chromatin structure and histone modification by utilizing fragment size post immunoprecipitation to integrate nucleosome density, determined by MNase accessibility, with histone modification measurements. Application of ndChIP-seq to primary cells and tissues will provide novel insights into the integrative nature of epigenetic regulation and permit identification of epigenetic signatures due to heterogeneity within the population.

The eukaryotic genome is packaged into chromatin via repeating nucleosome structures that consist of two copies of four histone proteins (e.g., H2A, H2B, H3, and H4) circumscribed by 146 base pairs of DNA1,2. Chromatin remodeling complexes control nucleosome position within gene promoter boundaries and participate in the regulation of gene expression by altering accessibility of the DNA to transcription factors and to the RNA polymerase machinery3,4.
Amino terminal tails of histones within the nucleosome are subjected to various covalent modifications, including acetylation, methylation, phosphorylation, ubiquitylation, sumoylation, formylation, and hydroxylation of specific amino acids5,6,7,8. Positions and degrees of these modifications dictate a chromatin state that influence chromatin structure and control access of the molecular complexes that allow activation of transcription7. Given that both nucleosome density and histone modification play a role in the local control of gene transcription, we developed a native ChIP approach that enables the simultaneous measurement of nucleosome density and histone modification9,10.
Native ChIP-seq takes advantage of the endonuclease micrococci nuclease (MNase) to digest intact chromatin in its native state within the nucleus11,12, a property that has been leveraged to map nucleosome positioning13,14,15. Nucleosome density ChIP-seq (ndChIP-seq) takes advantage of the property of preferential access of MNase to open regions of chromatin to generate measurements that combine MNase accessibility with histone modification10. ndChIP-seq is suitable for the profiling of histone modifications in rare primary cells, tissues, and cultured cells. Here, we present a detailed protocol that enables the generation of sequence datasets suitable for a previously described analytical frame work10 that integrates fragment size post immunoprecipitation, determined by paired-end read boundaries, to simultaneously investigate MNase accessibility with histone modification measurements. Previously, application of this protocol to 10,000 primary human cord blood derived CD34+ cells and human embryonic stem cells revealed unique relationships between chromatin structure and histone modifications within these cell types10. Given its ability to simultaneously measure nucleosome accessibility and histone modification, ndChIP-seq is capable of revealing epigenomic features in a cell population at a single nucleosome level, and resolving heterogeneous signatures into their constituent elements. An example of the exploration of heterogeneous cellular populations by ndChIP-seq is investigation of bivalent promoters, where both H3K4me3, an active mark, and H3K27me3, a repressive mark, are present10.

<table><tbody><tr><td>1M Tris-HCl &amp;ndash;pH 7.5</td><td>Thermo Scientific</td><td>15567-027</td><td></td></tr><tr><td>1M Tris-HCl &amp;ndash;pH 8</td><td>Thermo Scientific</td><td>15568-025</td><td></td></tr><tr><td>0.5M EDTA</td><td>Thermo Scientific</td><td>AM9260G</td><td></td></tr><tr><td>5M NaCl</td><td>Sigma</td><td>1001385276</td><td></td></tr><tr><td>Triton X-100</td><td>Sigma</td><td>1001412354</td><td></td></tr><tr><td>Sodium-Deoxycholate</td><td>Sigma</td><td>1001437582</td><td></td></tr><tr><td>SDS</td><td>Thermo Scientific</td><td>15525-017</td><td></td></tr><tr><td>Sodium-Bicarbonate</td><td>Fisher Scientific</td><td>S233-500</td><td></td></tr><tr><td>100% EtOH</td><td>NA</td><td>NA</td><td></td></tr><tr><td>V-bottom 96 well plate (AB 1400)</td><td>Thermo Scientific</td><td>AB-1400-L</td><td></td></tr><tr><td>Gilson P2 pipetman</td><td>Mandel</td><td>F144801</td><td></td></tr><tr><td>Gilson P10 pipetman</td><td>Mandel</td><td>F144802</td><td></td></tr><tr><td>Gilson P20 pipetman</td><td>Mandel</td><td>F123600</td><td></td></tr><tr><td>Gilson P100 pipetman</td><td>Mandel</td><td>F123615</td><td></td></tr><tr><td>Gilson P200 pipetman</td><td>Mandel</td><td>F123601</td><td></td></tr><tr><td>Gilson P1000 pipetman</td><td>Mandel</td><td>F123603</td><td></td></tr><tr><td>Micrococcal Nuclease&amp;nbsp;</td><td>NEB</td><td>M0247S</td><td></td></tr><tr><td>Thermo Mixer C (Heating block mixer)</td><td>Eppendorf</td><td>5382000023</td><td></td></tr><tr><td>Multi 12-channel Pippet P20</td><td>Rainin</td><td>17013803</td><td></td></tr><tr><td>Multi 12-channel Pippet P200</td><td>Rainin</td><td>17013805</td><td></td></tr><tr><td>1.5 ml LoBind tube</td><td>Eppendorf</td><td>22431021</td><td></td></tr><tr><td>0.5 ml LoBind tube</td><td>Eppendorf</td><td>22431005</td><td></td></tr><tr><td>Plastic Plate Cover</td><td>Edge Bio</td><td>48461</td><td></td></tr><tr><td>PCR cover</td><td>Bio Rad</td><td>MSD-1001</td><td></td></tr><tr><td>Aluminum Plate Cover</td><td>Bio Rad</td><td>MSF-1001</td><td></td></tr><tr><td>Elution buffer (EB buffer)</td><td>Qiagen</td><td>19086</td><td></td></tr><tr><td>1M DTT</td><td>Sigma</td><td>646563</td><td></td></tr><tr><td>Eppendorf 5810R centrifuge&amp;nbsp;</td><td>Eppendorf</td><td>22625004</td><td></td></tr><tr><td>Ultrapure water</td><td>Thermo Scientific</td><td>10977-015</td><td></td></tr><tr><td>Protein G dynabeads</td><td>Thermo Scientific</td><td>10001D</td><td></td></tr><tr><td>Protein A dynabeads</td><td>Thermo Scientific</td><td>10001D</td><td></td></tr><tr><td>Protease inhibitor Cocktail</td><td>Calbiochem</td><td>539134</td><td></td></tr><tr><td>Rotating platform</td><td>Mandel</td><td>1b109-12052010</td><td></td></tr><tr><td>Plate magnet</td><td>Alpaqua</td><td>2523</td><td></td></tr><tr><td>Domed 12-cap strip</td><td>Bio Rad</td><td>TCS1201</td><td></td></tr><tr><td>Buffer G2</td><td>Qiagen</td><td>1014636</td><td></td></tr><tr><td>Protease</td><td>Qiagen</td><td>19155</td><td></td></tr><tr><td>Tube Magnet (DynaMag-2)</td><td>Thermo Scientific</td><td>12321D</td><td></td></tr><tr><td>Tube Magnet (DynaMag-2)</td><td>LabCore</td><td>730-006</td><td></td></tr><tr><td>V shape Plastic reservoir</td><td>Mandel</td><td>S0100A</td><td></td></tr><tr><td>Vortex</td><td>Mandel</td><td>C1801</td><td></td></tr><tr><td>Mini Fuge</td><td>Mettler Toledo</td><td>XS2035</td><td></td></tr><tr><td>Analytical scale</td><td>Mandel</td><td>LB109-12052010</td><td></td></tr><tr><td>Quick Ligation Reaction Buffer, 5X</td><td>NEB</td><td>B6058S</td><td></td></tr><tr><td>DNA Polymerase I, Large (Klenow) Fragment</td><td>NEB</td><td>M0210S</td><td></td></tr><tr><td>Klenow Fragment (3&#039;-5&#039; exo)</td><td>NEB</td><td>M0212S</td><td></td></tr><tr><td>T4 DNA Polymerase</td><td>NEB</td><td>M0203S</td><td></td></tr><tr><td>T4 Polynucleotide Kinase</td><td>NEB</td><td>M0201S</td><td></td></tr><tr><td>Deoxynucleotide Solution mix, 10mM</td><td>NEB</td><td>N0447S</td><td></td></tr><tr><td>dATP Solution 10mM</td><td>NEB</td><td>N0440S</td><td></td></tr><tr><td>Quick T4 DNA Ligase</td><td>NEB</td><td>M0202T</td><td></td></tr><tr><td>Adenosine 5&#039;-Triphosphate (ATP), 25mM</td><td>NEB</td><td>P0756S</td><td></td></tr><tr><td>DNA Polymerase</td><td>Thermo Scientific</td><td>F549L</td><td></td></tr><tr><td>NEBuffer 2</td><td>NEB</td><td>B7002S</td><td></td></tr><tr><td>Hank&#039;s buffered salt solution</td><td>Thermo Scientific</td><td>14025076</td><td></td></tr><tr><td>Fetal bovine serum&amp;nbsp;</td><td>Thermo Scientific</td><td>A3160702</td><td></td></tr><tr><td>phosphate buffer saline&amp;nbsp;</td><td>Thermo Scientific</td><td>10010023</td><td></td></tr><tr><td>H3K4me3</td><td>Cell Signaling</td><td>9751S</td><td></td></tr><tr><td>H3K4me1</td><td>Diagenode</td><td>C15410037</td><td></td></tr><tr><td>H3K27me3</td><td>Diagenode</td><td>pAb-069-050</td><td></td></tr><tr><td>H3K36me3</td><td>Abcam</td><td>ab9050</td><td></td></tr><tr><td>H3K9me3</td><td>Diagenode</td><td>C15410056</td><td></td></tr><tr><td>SeraMag&amp;nbsp; super-paramagnetic beads</td><td></td><td></td><td></td></tr></tbody></table>

generation of native chromatin immunoprecipitation sequencing libraries for nucleosome density analysis

We present a modified native chromatin immunoprecipitation sequencing (ChIP-seq) experimental protocol compatible with a Gaussian mixture distribution based analysis methodology (nucleosome density ChIP-seq; ndChIP-seq) that enables the generation of combined measurements of micrococcal nuclease (MNase) accessibility with histone modification genome-wide. Nucleosome position and local density, and the posttranslational modification of their histone subunits, act in concert to regulate local transcription states. Combinatorial measurements of nucleosome accessibility with histone modification generated by ndChIP-seq allows for the simultaneous interrogation of these features. The ndChIP-seq methodology is applicable to small numbers of primary cells inaccessible to cross-linking based ChIP-seq protocols. Taken together, ndChIP-seq enables the measurement of histone modification in combination with local nucleosome density to obtain new insights into shared mechanisms that regulate RNA transcription within rare primary cell populations.

Watch this Scientific Journal Video about Generation of Native Chromatin Immunoprecipitation Sequencing Libraries for Nucleosome Density Analysis at JoVE.com

Generation of Native Chromatin Immunoprecipitation Sequencing Libraries for Nucleosome Density Analysis

We present a modified native chromatin immunoprecipitation sequencing (ChIP-seq) methodology for the generation of sequence datasets suitable for a nucleosome density ChIP-seq analytical framework integrating micrococcal nuclease (MNase) accessibility with histone modification measurements.

We present a modified native chromatin immunoprecipitation sequencing (ChIP-seq) experimental protocol compatible with a Gaussian mixture distribution ...

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JoVE Journal

Genetics

22.0K Views.  University of British Columbia. We present a modified native chromatin immunoprecipitation sequencing (ChIP-seq) methodology for the generation of sequence datasets suitable for a nucleosome density ChIP-seq analytical framework integrating micrococcal nuclease (MNase) accessibility with histone modification measurements.

Video: Generation of Native Chromatin Immunoprecipitation Sequencing Libraries for Nucleosome Density Analysis

Chromatin Immunoprecipitation (ChIP) Protocol for Low-abundance Embryonic Samples

Chromatin immunoprecipitation (ChIP) is a widely-used technique for mapping the localization of post-translationally modified histones, histone variants, transcription factors, or chromatin-modifying enzymes at a given locus or on a genome-wide scale. The combination of ChIP assays with next-generation sequencing (i.e., ChIP-Seq) is a powerful approach to globally uncover gene regulatory networks and to improve the functional annotation of genomes, especially of non-coding regulatory sequences. ChIP protocols normally require large amounts of cellular material, thus precluding the applicability of this method to investigating rare cell types or small tissue biopsies. In order to make the ChIP assay compatible with the amount of biological material that can typically be obtained in vivo during early vertebrate embryogenesis, we describe here a simplified ChIP protocol in which the number of steps required to complete the assay were reduced to minimize sample loss. This ChIP protocol has been successfully used to investigate different histone modifications in various embryonic chicken and adult mouse tissues using low to medium cell numbers (5 x 104 - 5 x 105 cells). Importantly, this protocol is compatible with ChIP-seq technology using standard library preparation methods, thus providing global epigenomic maps in highly relevant embryonic tissues.

Chromatin Immunoprecipitation ChIP Protocol for Low-abundance Embryonic Samples

Here, we describe a chromatin immunoprecipitation (ChIP) and ChIP-seq library preparation protocol to generate global epigenomic profiles from low-abundance chicken embryonic samples.

Chromatin immunoprecipitation (ChIP) is a widely-used technique for mapping the localization of post-translationally modified histones, histone variants, ...

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

Chromatin Immunoprecipitation of Murine Brown Adipose Tissue

Most cellular processes are regulated by transcriptional modulation of specific gene programs. Such modulation is achieved through the combined actions of a wide range of transcription factors (TFs) and cofactors mediating transcriptional activation or repression via changes in chromatin structure. Chromatin immunoprecipitation (ChIP) is a useful molecular biology approach for mapping histone modifications and profiling transcription factors/cofactors binding to DNA, thus providing a snapshot of the dynamic nuclear changes occurring during different biological processes.
To study transcriptional regulation in adipose tissue, samples derived from in vitro cell cultures of immortalized or primary cell lines are often favored in ChIP assays because of the abundance of starting material and reduced biological variability. However, these models represent a limited snapshot of the actual chromatin state in living organisms. Thus, there is a critical need for optimized protocols to perform ChIP on adipose tissue samples derived from animal models.
Here we describe a protocol for efficient ChIP-seq of both histone modifications and non-histone proteins in brown adipose tissue (BAT) isolated from a mouse. The protocol is optimized for investigating genome-wide localization of proteins of interest and epigenetic markers in the BAT, which is a morphologically and physiologically distinct tissue amongst fat depots.

Here we describe a protocol for efficient chromatin immunoprecipitation (ChIP) followed by high-throughput DNA sequencing (ChIP-seq) of brown adipose tissue (BAT) isolated from a mouse. This protocol is suitable for both mapping histone modifications and investigating genome-wide localization of non-histone proteins of interest in vivo.

Most cellular processes are regulated by transcriptional modulation of specific gene programs. Such modulation is achieved through the combined actions of ...

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 ...

Biology

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.

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 ...

Automating ChIP-seq Experiments to Generate Epigenetic Profiles on 10,000 HeLa Cells

Chromatin immunoprecipitation followed by next generation sequencing (ChIP-seq) is a technique of choice for studying protein-DNA interactions. ChIP-seq has been used for mapping protein-DNA interactions and allocating histones modifications. The procedure is tedious and time consuming, and one of the major limitations is the requirement for high amounts of starting material, usually millions of cells. Automation of chromatin immunoprecipitation assays is possible when the procedure is based on the use of magnetic beads. Successful automated protocols of chromatin immunoprecipitation and library preparation have been specifically designed on a commercially available robotic liquid handling system dedicated mainly to automate epigenetic assays. First, validation of automated ChIP-seq assays using antibodies directed against various histone modifications was shown, followed by optimization of the automated protocols to perform chromatin immunoprecipitation and library preparation starting with low cell numbers. The goal of these experiments is to provide a valuable tool for future epigenetic analysis of specific cell types, sub-populations, and biopsy samples.

Methods for mapping in vivo protein-DNA interactions are becoming crucial for every aspect of genomic research but they are laborious, costly, and time consuming. Here a commercially available robotic liquid handling system that automates chromatin immunoprecipitation for mapping in vivo protein-DNA interactions with limited amounts of cells is presented.

Chromatin immunoprecipitation followed by next generation sequencing (ChIP-seq) is a technique of choice for studying protein-DNA interactions. ChIP-seq ...

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 ...

Strand-Specific Analysis of Proteins at Replicating DNA Strands by Enrichment and Sequencing of Protein-Associated Nascent DNA Method

Genome duplication is orchestrated by replisome proteins, including helicases, which unwind double-stranded DNA into individual antiparallel single strands, each requiring distinct modes of replication: continuous (leading) and discontinuous (lagging). Understanding the interactions of chromatin-associated proteins with replicating DNA strands in vivo is crucial for elucidating the mechanisms of chromatin assembly and DNA repair coupled to DNA replication. This protocol presents the enrichment and sequencing of protein-associated nascent DNA (eSPAN) method, designed to quantify relative protein levels on nascent leading and lagging DNA strands at replication forks. The eSPAN procedure starts with chromatin immunoprecipitation (ChIP, in yeast) or cleavage under targets and tagmentation (CUT&amp;Tag; in mammalian cells) of a protein of interest, followed by enrichment of the protein-associated nascent DNA by bromodeoxyuridine (BrdU) immunoprecipitation. Strand-specific next-generation sequencing is applied to isolated ssDNA. This technique can be used to determine whether a protein is enriched at leading or lagging replication forks. The eSPAN provides genome-wide strand-preference of chromatin-associated proteins, including histones at replication forks.

Enrichment and sequencing of protein-associated nascent DNA (eSPAN) was developed to detect the relative abundance of a chromatin-associated protein on two replicating DNA strands, thereby revealing molecular insight into chromatin replication and its coupled processes. This protocol describes eSPAN procedures in yeast and mouse embryonic stem (ES) cells.

Genome duplication is orchestrated by replisome proteins, including helicases, which unwind double-stranded DNA into individual antiparallel single ...

Chromatin Immunoprecipitation to Identify Target Protein Binding Sites on Genomic DNA

Source: Dong, X., et.al., <a href="https://app.jove.com/v/57547">Identifying Transcription Factor Olig2 Genomic Binding Sites in Acutely Purified PDGFR&#945;+ Cells by Low-cell Chromatin Immunoprecipitation Sequencing Analysis.</a>&#160;J. Vis. Exp.&#160;(2018)
In this video, we demonstrate the chromatin immunoprecipitation technique to identify protein binding sites on specific regions of the genomic DNA of oligodendrocyte precursor cells via the selective immunoprecipitation of protein-bound chromatin fragments. This method helps to study the interaction of several regulatory proteins, including transcription factors involved in gene regulation.

Source: Dong, X., et.al., Identifying Transcription Factor Olig2 Genomic Binding Sites in Acutely Purified PDGFR&#945;+ Cells by Low-cell Chromatin ...