Extended Data Fig. 4: RBBP5-mediated interactions with NCP, ubiquitin and other subunits of MLL1.

a, b, Density maps of the RBBP5^WD40 loops that interact with the histone H2B–H4 cleft, shown in stereo mode. c, Density maps of the H2BK120-conjugated ubiquitin from different 3D classes of the MLL1–ubNCP dataset, shown in stereo mode. The major and minor conformations of RBBP5^WD40–H2BK120ub1 are classified on the basis of the percentage of each 3D class from the masked 3D classification of the RBBP5^WD40–H2BK120ub1 region. The masked 3D classification was repeated at least three times with similar results. d, Different binding modes of the H2BK120-conjugated ubiquitin to RBBP5^WD40 in the MLL3–ubNCP dataset. The major and minor conformations of H2BK120ub1 are classified on the basis of the percentage of each 3D class from masked 3D classification of the RBBP5^WD40–H2BK120ub1 region. The masked 3D classification was repeated at least three times with similar results. e, Superposition of all the identified RBBP5^WD40–ubiquitin structures from the MLL1–ubNCP and MLL3–ubNCP datasets reveals the movement of H2BK120ub1 between the α-helix-containing loop of RBBP5^WD40 and the junction between WDR5 and RBBP5^WD40 junction. f, The input of the HMT reactions related to Fig. 2d. The input amounts of the wild-type and mutant MLL1 complexes were quantified according to the band intensities of WDR5. The gel band that results from the incomplete protease 3C digestion of 6×His3C–ubiquitin–H2B is denoted with an asterisk. g, Overview of the structure of the MLL1 complex, showing the cryo-EM density maps of the RBBP5 N- and C-terminal loop regions. The N terminus of RBBP5 (RBBP5^N-ter), activation segment and ASH2L-binding motif of RBBP5 (RBBP5^AS-ABM), WDR5-binding motif of RBBP5 (RBBP5^WBM) and C terminus of RBBP5 (RBBP5^C-ter) are coloured in orange, green, cyan, and yellow, respectively. Loop regions of RBBP5 assemble the subunits of the MLL enzyme into an integral complex, through multiple interactions.