The nucleosome is made up of four core histone proteins (H2A, H2B, H3 and H4) and is the primary building block of chromatin. The N-terminal tail of core histones undergoes multiple different post-transcriptional modifications including acetylation, phosphorylation, ubiquitination, methylation, and ADP-ribosylation. These modifications occur in response to cell signal stimuli and have a direct effect on gene expression. Acetylation of histone H4 plays a primary role in the structural changes that mediate enhanced binding of transcription factors to their recognition sites within nucleosomes. It has been suggested that acetylated Histone H4 also is involved in heightened activation of the transcription of male X chromosomes, and that Histone H4 stimulates glucose transport activity in rat skeletal muscle.Synonyms: H4/A, H4FA, HIST1H4