TIP60/Kat5 facilitates the repressive action of HDAC4 through the formation of complexes with the zinc-finger transcription factor KLF4 [400,401], the cAMP-dependent transcription factor ATF3 [402,403,404] and the neurodegenerative disease protein ataxin-1 (ATXN1) [405,406] (Figure 20B). Here, HDAC4 is linked to glycogen storage disease VI.