Histones are a family of proteins found in eukaryotic cell nuclei that play a fundamental role in the organization and compaction of DNA into chromatin, the structure that packages and regulates access to DNA. They are highly conserved across species and possess several key features critical to their function in chromatin structure and gene regulation. Histones are characterized by a high content of positively charged amino acids, particularly lysine and arginine. These positively charged amino acids facilitate the binding of histones to the negatively charged phosphate groups of DNA. Structurally, histones have a globular domain, known as the histone core, and a flexible N-terminal tail. The histone core consists of three alpha helices and two loops, which form a protein octamer. There are five major histone families: H1, H2A, H2B, H3, and H4. Each nucleosome, the basic repeating unit of chromatin, contains two molecules each of histones H2A, H2B, H3, and H4. Histone H1 - often called the linker histone - is associated with the DNA linker region between nucleosomes and aids in higher-order chromatin compaction. Histones combine with DNA to form nucleosomes, the structural units of chromatin. DNA wraps approximately 1.65 turns around the histone octamer, resulting in 147 base pairs of DNA in each nucleosome. This acts to protect DNA and facilitates its compaction. Histones are subject to a variety of regulatory post-translational modifications, including acetylation, methylation, phosphorylation and ubiquitylation. These modifications occur on specific amino acids within the histone tails. Acetylation of histone lysines typically results in a more open chromatin structure, making DNA more accessible for transcription factors and RNA polymerase, thereby promoting gene expression. Methylation of histone lysines or arginines can either activate or repress gene transcription, depending on the specific histone residue and the number of methyl groups added. Phosphorylation and ubiquitylation of histones often occur during cell division and DNA repair processes. Phosphorylated histones are thought to promote a more compact chromatin structure, making it easier to separate sister chromatids during cell division. Histone ubiquitylation plays a role in regulating DNA damage repair. For example, the ubiquitin-binding domains of various DNA repair proteins, such as 53BP1 and BRCA1, recognize ubiquitylated histones and are recruited to sites of DNA damage, facilitating the assembly of repair complexes at DNA lesions. Combinations of histone modifications, known as histone codes, determine the accessibility of chromatin to transcriptional machinery. These codes are dynamic and can change in response to cellular signals and environmental cues. Histone modifications are read and interpreted by various chromatin-binding proteins that influence gene expression and chromatin structure. The positioning of nucleosomes along DNA affects the accessibility of specific DNA sequences to transcription factors and other regulatory proteins. Histones can exist in different variants, with small variations in amino acid sequence. These variants can contribute to specialized functions, with histone H2A.Z, for example, associated with gene regulation. Finally, during DNA replication and cell division, histones and their post-translational modifications are faithfully inherited by daughter cells, ensuring the transmission of epigenetic information to progeny cells. We offer a large product range of research tools for investigating histones, including Histone H3 antibodies, Histone H4 antibodies, Histone H2B antibodies, Histone H1 antibodies, and Histone H2A.X antibodies. Explore our full histones product range below and discover more, for less. Alternatively, you can explore our H3, H4, and Variants product ranges.