The NuA4 complex contains the histone acetyltransferase (HAT) KAT5 (TIP60), a member of the MYST family. The first characterisation of a mammalian NuA4 complex identified the additonal components TRRAP, the Enhancer of Polycomb protein (EPC1), actin-like protein ACTL6A (BAF53a), which is a homolog of yeast Arp4, actin (ACTB), the SNF2-related helicase p400 (EP400) and the AAA ATPases RUVBL1 (TIP49a) and RUVBL2 (TIP49b) (Ikura et al. 2000). Subsequently further copmponents were identified as MRGBP, MORF4L1 (MRG15), MORF4L2 (MRGX), (Cai et al. 2003), BRD8, DMAP1, ING3, MEAF6, YEATS4 (Doyon et al. 2004) and VPS72 (YL1) (Cai et al. 2005).