Unique binding of H3 tail peptide by NURD but not other class I HDAC complexes. A. Coomassie blue staining revealed the H3 tail peptide-binding proteins isolated from HeLa nuclear extracts. The identities of the protein bands were determined by mass spectrometry. ‘-‘, the beads only control. B. Among several class I HDAC complexes only NURD exhibited a substantial H3 tail-binding activity in vitro. The HeLa nuclear extracts were incubated with various immobilized histone tails in vitro and the binding of various class I HDAC complexes was examined by western blot analysis using antibodies against complex-specific subunits. Sin3A, the unique subunit of the Sin3A/HDAC1/2 complex; CoREST, the unique subunit of CoREST complex; MTA1/2, the unique subunits of NURD; NCoR, the unique subunit of NCoR/SMRT/HDAC3 complex. C. The binding specificity of NURD complexes toward histone H3 tail peptides. The HeLa nuclear extracts were incubated with the immobilized histone tail peptides as indicated and the binding of NURD complexes was examined by subsequent western blot analysis using antibodies against CHD3, CHD4, MTA1 and HDAC1. PHF8 served as a positive control for H3K4me2/3-binding proteins.