Figure 2. Interaction of DNMT3L with the N terminus of histone H3 is abolished by methylation of H3 lysine 4.

a, Peptide interaction assays with unmodified histone tails as indicated, incubated with full-length human DNMT3L. DNMT3L interacts only with the N-terminal tail of H3 (left), and this interaction requires only the first seven amino acids of H3 (right). b, Peptide interaction assays with DNMT3L and modified histone tails as indicated. DNMT3L bound only to the H3 tail that is unmodified at lysine 4. c, WDR5 (WD repeat domain 5) and the chromodomain of HP-1α (heterochromatin protein 1α) were used as controls for peptide binding specificity. d, Dissociation constants as determined by fluorescence polarization with C-terminal fluoresceinated peptides. K_d values are shown on the right. The 18-fold increase in K_d caused by monomethylation of H3 lysine 4 prevented detection of DNMT3L binding in b. e, Histones associated with DNMT3L in vivo are depleted in H3 that is trimethylated at lysine 4. Nuclear extract was treated with micrococcal nuclease before immunoprecipitation followed by separation of proteins by SDS-polyacrylamide gel electrophoresis. Immunoblot was performed with the antibodies indicated. A specific depletion in H3 trimethylated at lysine 4 can be seen in the fourth immunoblot from the top.