Extended Data Figure 2. Models and sequence alignment of TONSL ARD.

a, Pull-down assay of recombinant ARD with GST-H3 tail (a.a. 1–59) and GST-H4 tail (a.a. 1–31). b, Modelling of TONSL ARD on the co-chaperone structure of MCM2 HBD and ASF1 in complex with an H3–H4 dimer. When comparing the structure of the TONSL ARD–MCM2 HBD–H3–H4 tetramer complex with our previous structure of the MCM2 HBD–H3–H4 dimer–ASF1 complex (PDB 5BNX, Huang H. et al. NSMB 2015), the common parts of both structures superimposed well with a small r.m.s.deviation of 0.44 Å. A model of the quinary complex composed of one molecule of each protein TONSL ARD, MCM2 HBD, ASF1, H3 and H4, was made after superposition. This model shows that TONSL ARD, MCM2 HBD and ASF1 could simultaneously bind an H3–H4 dimer without steric clash. c, Model of TONSL ARD on the structure of the nucleosome. The model was generated by a direct superposition of the H3–H4 tetramer in the structure of the TONSL ARD–MCM2 HBD–H3–H4 tetramer complex onto the H3–H4 tetramer in the nucleosome structure (PBD 3AV2). There was no adjustment in the conformation of the model and no steric clash in the model. The MCM2 HBD molecules were omitted from the model for clarity. d, Alignment of TONSL ARD (512–692) sequences from H. sapiens, M. musculus, X. laevis and D. rerio. The secondary structures of human TONSL ARD are showed on top of the sequence alignment. Stars (*) indicate the highly conserved residues that constitute the H4 tail-binding surface of TONSL ARD and the three strictly conserved acidic residues forming hydrogen bonds with the key residue H4 Lys20 are highlighted with red stars ‘*’.