Histone H4 acetylation at lysine 5 (H4K5ac) is a post-translational modification that plays a significant role in chromatin structure and function. This modification is catalyzed by histone acetyltransferases (HATs), which transfer an acetyl group from acetyl-coenzyme A (acetyl-CoA) to the ε-amino group of the lysine residue on histone H4. The acetylation of histone H4 at lysine 5 is crucial for various cellular processes, including gene activation, DNA replication, and cell cycle progression. It is involved in providing a more open chromatin structure, which is generally permissive for the binding of transcription factors and the assembly of the transcription machinery. Additionally, H4K5ac has been linked to the deposition of the histone H3 variant CENP-A into centromeres, which is essential for proper chromosome segregation during cell division.