ChIP assays and modified histone antibodies

August 20th, 2011 |

The histones are highly conserved nuclear proteins which package and process the DNA of eukaryotic cells, providing structure and order to the chromosome. Modified histones are those which have undergone post-translational modification. We at Novus Biologicals have a large antibody catalog of histone and modified histone antibodies, including our Epi-PlusTM antibody line, which have proven invaluable in chromatin immunoprecipitation (ChIP) assays.

The various histones are grouped into six distinct classes. Four of these: H2A, H2B, H3 and H4, form the octamer core of the nucleosome, around which the DNA is wound to form chromatin. Antibody labeling has shown that in addition to packaging DNA, the histones play a vital role in gene regulation due to their various post-translational modifications. These take place at specific amino acid residues of the N-terminal tail domains.

The most common modification, methylation, tightens the DNA-binding structure and down-regulates the transcription of genes. Acetylation, however, activates transcription by forming looser bindings. Phosphorylation, another type of modification, is associated with H3 acetylation resulting from mitogenesis or stress. Others include ADP-ribosylation; citrullination; ubiquitination and sumoylation. Each modification may target a number of residues; therefore a common nomenclature has been applied to modified histones, which is also used in the histone antibody database. For example, the H3K4me3 antibody targets the H3 histone, trimethylated at the Lysine 4 position.

Histone and modified histone antibodies are widely used in ChIP assays, including the recently developed ChIP-on-chip method. Scientists use ChIP-grade antibodies to study DNA/protein interactions, and to investigate certain genomic locations in relationship to specific proteins. ChIP analysis is also used to investigate the association of specific genomic regions with certain histone modifications, as well as how those modified histones affect other genes.

Combining modified histone antibodies with modern ChIP-on-chip analysis has proven a highly effective tool for determining patterns of histone modification at a genome-wide level. By providing an extensive antibody database of ChIP-grade modified histone antibodies, Novus remains a vital resource to those studying epigenetics and the histone code.