HAT1 also known as KAT1 is a type B histone acetyltransferase (HAT) that is involved in the rapid acetylation of newly synthesized cytoplasmic histones, which are in turn imported into the nucleus for de novo deposition onto nascent DNA chains. plays a crucial role in the acetylation of histones, specifically targeting histone H4, which is essential for the regulation of gene expression. The acetylation process mediated by HAT1 not only alters the interaction between histones and DNA, thereby facilitating a more open chromatin structure, but also serves as a signal for the recruitment of transcriptional machinery, making HAT1 vital for proper cellular function and development.