In vitro binding assay

For histone peptide binding, 1 μg of biotinylated histone peptides was incubated with 15 μl of Dynabeads MyOne Streptavidin T1 (Invitrogen, 65601) in binding/washing buffer (50 mM tris-HCl 7.5, 300 mM NaCl, 0.5% NP-40, and 1 mM phenylmethylsulfonyl fluoride + protease inhibitors) at 25°C for 1 hour with shaking at 1100 rpm. After washing away the nonmobilized histone peptides, 1 μg of recombinant proteins (His-SUMO-PHDZMP or His-SUMO-ZMP-ΔPHD) in binding/washing buffer was added and incubated for 2 hours at 4°C with rotation. The beads were washed five times with binding/washing buffer, and the bound proteins were denatured and eluted by heating the beads at 95°C for 5 min. The proteins were subsequently resolved in 12.5% SDS-PAGE gels and analyzed by Western blotting with 6× His antibody (MilliporeSigma, 05-949) used at 1:5000 dilution.