Figure 7.

Model for HDAC1 relationship with CCT and HDAC complexes. Previously, Guenther et al.⁸ proposed that HDAC3 is primed by binding to the CCT complex prior to binding the corepressor SMRT with release of CCT. Similarly, we suggest that HDAC1 might associate with CCT for ATP-dependent folding⁴⁷ prior to assembly into Sin3, NuRD or CoREST complexes, with this process influenced by the presence of an N-terminal Halo tag. In parallel with previous evidence that CCT binds to and facilitates folding of two β strands within the VHL protein⁶⁶, the CCT complex might facilitate folding of the β sheet within HDAC1 (indicated by green ribbons in the HDAC1 structure (PDB 4BKX⁶¹, visualized using Chimera⁶²) with the N-terminal β strand shown in red); an N-terminal Halo tag might prevent process of HDAC1 folding or of HDAC1 release by CCT for incorporation into HDAC complexes.