Western Blot Analysis of H3K4 Methylation

To examine H3K4 methylation or epitope-tagged H3, cell extracts were prepared following the bead-beat procedure as described66 (link). A twofold serial dilution of extracts were resolved in 15% SDS–PAGE and transferred onto a polyvinylidene difluoride (PVDF) membrane. The following antibodies were used in western blotting (dilutions used, source and catalogue numbers are indicated within parentheses): α-H3K4me1 (1:1,000, Active Motif, 39,297), α-H3K4me2 (1:10,000, Millipore, 07–030), α-H3K4me3 (1:7,500, Active Motif, 39,159), α-V5 (1:50,000, Bio-Rad, MCA1360) and α-Flag (1:5,000, Sigma, F3165). The histone H3 loading was monitored using α-H3 (1:2,000, Abcam, ab46765). Full-length images of the blots are shown in Supplementary Figs 20–22.