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Internally Calibrated ChIP-seq (ICeChIP-seq) using a large panel of antibodies against H3K4 methylations to measure genome-wide histone modification density in mammalian cells

ABSTRACT: Post-translational modifications (PTMs) on histone proteins regulate genome accessibility and are frequently studied using chromatin immunoprecipitation (ChIP). In ChIP, an antibody putatively specific towards a histone PTM is used to map its genomic locations. ChIP experiments assume perfect antibody-epitope specificity, an assumption previously shown to be problematic, largely through peptide array studies. Among the most well-studied histone PTMs are the mono-, di-, and tri-methylation states of histone H3 lysine 4 (H3K4). While each state has been ascribed different biological functions, the methylation state specificity of antibodies used in these studies has not been systematically interrogated. Here, we use internally calibrated ChIP (ICeChIP) to comprehensively define the specificities of 52 commercially available antibodies marketed to distinguish the three methylation states of H3K4, allowing identification of both high- and low-specificity antibodies. We then conduct ICeChIP-seq with 18 such antibodies of varying specificity. We further find that the sum of H3K4me1 and H3K4me2 across enhancers contacting a promoter correlates strongly with gene expression for all genes, including housekeeping genes, and note that use of low-quality antibodies yields materially different biological interpretations. These results illustrate the way by which variable specificity of commercial antibodies contributes to the “reproducibility crisis” in biological research and demonstrates the need to carefully validate antibodies with techniques appropriate for the intended applications.

ORGANISM(S): Mus musculus Homo sapiens

PROVIDER: GSE103543 | GEO | 2018/09/20

REPOSITORIES: GEO

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Project description:Global analysis of H3K4 methylation defines MLL family member targets and points to a role for MLL1-mediated H3K4 methylation in the regulation of transcriptional initiation by RNA polymerase II A common landmark of activated genes is the presence of trimethylation on lysine 4 of histone H3 (H3K4) at promoter regions. The Set1/COMPASS was the founding member and the only H3K4 methylases in S. cerevisiae, however, in mammals at least six H3K4 methylases Set1A/B and MLL1-4 are found in COMPASS-like complexes capable of methylating H3K4. To gain further insight into the different roles and functional targets for the H3K4 methylases, we have undertaken a genome-wide analysis of H3K4 methylation pattern in wild-type Mll1+/+ and Mll1-/- mouse fibroblasts (MEFs). We found that Mll1 is required for the H3K4 trimethylation of less than 5% of promoters carrying this modification. Many of these genes, which include developmental regulators such as Hox genes show decreased levels of RNA polymerase II recruitment and expression concomitant with the loss of H3K4 methylation. Although Mll1 is only required for the methylation of a subset of Hox genes, Menin, a component of the Mll1 and Mll2 complexes, is required for the overwhelming majority of H3K4 methylation at Hox loci. However, the loss of MLL3/4 and/or the Set1 complexes have little to no effect on the Hox loci H3K4 methylation or expression levels in these MEFs. Together these data provide insight into redundancy and specialization of COMPASS-like complexes in mammals and provide evidence on a possible role for Mll1-mediated H3K4 methylation in the regulation of transcriptional initiation. Chromatin Immunoprecipitation was performed with antibodies for histone 3 lysine 4 trimethylation, histone 3, and PolII in Mll1+/+ and Mll1-/- mouse embryonic fibroblasts. DNA was hybridized to a custom Agilent tiling array (4x44k format) that covers three of the hox regions (A,B,D) and a collection of other genes.

Dataset Information

Internally Calibrated ChIP-seq (ICeChIP-seq) using a large panel of antibodies against H3K4 methylations to measure genome-wide histone modification density in mammalian cells

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