Figure 4.

Subunit requirements for H3K4 methylation activities of human MLL3^Core and MLL4^Core complexes. (A) SDS-PAGE/Coomassie blue staining of purified MLL3^Core complexes lacking the indicated subunits. (B) Whole-cell extracts and purified MLL3^Core complexes prepared from Sf9 cells infected with baculoviruses in the absence of the indicated subunits were subjected to immunoblot analyses as in Figure 2B. (C and D) H3 (C) and H2Bub chromatin (D) substrates were subjected to in vitro HMT assays with the indicated concentrations of subunit-lacking MLL3^Core (left) and MLL4^Core (right) complexes. Note that because of weak H3K4 methylation activity (Figure 1), a much higher concentration of MLL3^Core complex (40 nM) than MLL4^Core complex (15 nM) was used for chromatin HMT assays.