Histone proteins help compact and organise the DNA of the nucleus and provide it with structural support, they also play key roles in orchestrating gene expression. The four core histones, H2A, H2B, H3 and H4 form a complex comprising an H3-H4 tetramer and two H2A-H2B dimers, known as the histone octamer core. Around this core, DNA is wound forming a DNA/histone complex known as the nucleosome. Between the nucleosome is the internucleosomal DNA which is stabilised by the linker histone H1.
The tail region of the four core histones is able to undergo modifications such as acetylation, methylation, phosphorylation, citrullination, SUMOylation and ubiquitination. These modifications can alter the properties of the chromatin regions in which they occur. For example acetylation generally results in the more open euchromatin state which allows more active transcription such as in H4 K5Ac, K8Ac, K12Ac K16Ac fluorescently labelled peptide. Methylation generally has the opposite effect and results in more closed heterochromatin and transcriptional repression such as H3 K23 trimethylation which has been associated with meiotic cell divisions. Hypermethylation is also seen in some cancer cells and can result in unchecked cell growth.
The modifications of core histones are carried out by histone modifying enzymes such as histone acetyltransferase (HATs) and histone deacetylases (HDACs), histone methyltransferases (HMTs) and lysine demethylases (KDMs) and kinases and phosphatases. These histone modifications can occur in different complex combinations; making up what is known as the “histone code”. Alterations in the histone modification patterns, often due to aberrant expression of histone modifying enzymes, have been seen in diseases such as cancers and autoimmune, cardiovascular and neurodegenerative disorders.
In addition to these histone modifications, the four core histones can be replaced in certain cells by histone variants which can further alter the nature of the chromatin and affect its level of compaction. Examples of such variants include: histone H3.3, often associated with pericentromeric or telomeric regions for which we have also raised antibodies; histone H2AB1 which creates an unconventional chromatin structure associated with active transcription and; γH2Ax which is associated with DNA double strand breaks, such as during meiosis for which we have also raised an antibody.
Here are some of our popular histone peptides and antibodies:
Anti-Histone H2B antibody crb2005165