Histone H2A is one of the five main histone proteins involved in the structure of chromatin in eukaryotic cells. The other histone proteins are: H1, H2B, H3 and H4. DNA Folding: H2A is important for packaging DNA into chromatin. Since H2A packages DNA molecules into chromatin, the packaging process will affect gene expression. H2A has been correlated with DNA modification and epigenetics. H2A plays a major role in determining the overall structure of chromatin. Inadvertently, H2A has been found to regulate gene expression. DNA modification by H2A occurs in the cell nucleus. Proteins responsible for nuclear import of H2A protein are karyopherin and importin. Recent studies also show that nucleosome assembly protein 1 is also used to transport of H2A into the nucleus so it can wrap DNA. Other functions of H2A have been seen in the histone variant H2A.Z. This variant is associated with gene activation, silencing and suppression of antisense RNA. In addition, when H2A.Z was studied in human and yeast cells, it was used to promote RNA polymerase II recruitment. Antimicrobial peptide: Histones are conserved eukaryotic cationic proteins present in the cells and are involved in the antimicrobial activities. In vertebrates and invertebrates, Histone H2A variant is reported to be involved in host immune response by acting as antimicrobial peptides (AMPs). H2A are α-helical molecule, amphipathic protein with hydrophobic and hydrophilic residues on opposing sides that enhances the antimicrobial activity of H2A.