All four histones have a common basic structure with a highly conserved globular domain and a flexible N-terminal tail, which can undergo post-translational modifications that affect their function. These modifications, such as acetylation, methylation, and phosphorylation, can regulate gene expression by changing the accessibility of DNA to the transcriptional machinery.

    H2A is a highly conserved histone that is involved in the regulation of DNA replication, transcription, and DNA damage repair.

    H2B is involved in chromatin condensation and has a role in gene expression regulation.

    H3 is the most abundant histone in the nucleosome and is involved in the regulation of gene expression and DNA replication.

    H4 is involved in the regulation of chromosome condensation, DNA replication, and gene expression.
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