Fig. 1

An illustration of the relationship between SET-domain histone binding and histone methylation. Set7/9 methyltransferase preferentially methylates SET-domain-associated histones H3. Bacterially expressed GST-tagged full-size SET7/9 protein, immobilized on glutathione–sepharose, was incubated for the indicated time with excess of HeLa cell core histones and 100 μg/ml BSA in the presence of ³H-S-adenosyl-methionine. The GST-SET beads were sequentially washed in buffers containing 0.2% of NP-40 and 0.2, 0.4, and 0.6 M NaCl. Bead-associated proteins (“bound”, bd—lanes 2 and 4) and TCA-precipitated pooled wash fractions (“unbound”, u—lanes 3 and 5) were resolved on an SDS gel and stained with Coomassie (top panel). The H3-containing slice was excised from gel, treated with EN3HANCE reagent (Perkin-Elmer), dried, and exposed to film. Lane 1 shows input histones in the reaction buffer