KAT7 or K (lysine) acetyltransferase 5 is a signaling protein that belongs to the MYST family of histone acetyl transferases (HATs) and was originally isolated as an HIV-1 TAT-interactive protein which play important roles in regulating chromatin remodeling, transcription and other nuclear processes by acetylating histone and non-histone proteins. KAT7 acts as a transcriptional inhibitor and inhibited AR-mediated transactivation of reporter constructs in CV-1 and PC-3 cells. KAT7 is part of a multisubunit complex that can acetylate histones H3 and H4.