expressed in the inactive X chromosome in females. Structure H2A consists of a main globular domain, an N-terminal tail and a C-terminal tail. Both tails are the location of post-translational modification. Thus far, researchers have not identified any secondary structures that arise in the tails. H2A utilizes a protein fold known as the ‘histone fold’. The histone fold is a three-helix core domain that is connected by two loops. This connection forms a ‘handshake arrangement.’ Most notably, this is termed the helix-turn-helix motif, which allows for dimerization with H2B. The ‘histone fold’ is conserved among H2A at the structural level; however the genetic sequence that encodes for this structure differs between variants. The structure of macroH2A variant was exposed through X-ray crystallography. The conserved domain contains a DNA binding structure and a peptidase fold. The function of this conserved domain remains unknown. Research suggests that this conserved domain may function as an anchor site for Xist DNA or it may also function as a modifying enzyme. Function 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. Genetics H2A is coded by many genes in the human genome, including: H2AFB1, H2AFB2, H2AFB3, H2AFJ, H2AFV, H2AFX, H2AFY, H2AFY2, and H2AFZ. Genetic patterns among the different