KAT5 and autoimmune disease: On the other hand, several independent investigations suggest that TIP60 acts a co-factor for Foxp3, the master regulator of regulatory T cells (Tregs), to prevent the pathogenesis of autoimmune diseases by promoting histone H4K16 acetylation on the Foxp3 target promoters and by directly acetylating and stabilizing Foxp3 (Chatila and Williams, 2012).