This is amino acids 1 to 7 fragment of the histone H4. Alterations in chromatin structure, such as nucleosome sliding, removal of nucleosomes, and disruption of DNA–histone or histone–histone contacts through post-translational modification of the histones, have been linked to transcriptional regulation, DNA damage repair, and replication, among other cellular processes. Modification of histones occurs primarily in the N-terminal residues or tail region. These modifications include phosphorylation, ubiquitinylation, methylation, sumolyation, and acetylation. Lys5 may serve as the acetylation site for this peptide.