Mechanism of histone lysine methyl transfer revealed by the structure of SET7/9-AdoMetKwon, T., Chang, J.H., Kwak, E., Lee, C.W., Joachimiak, A., Kim, Y.C., Lee, J., Cho, Y.
(2003) EMBO J 22: 292-303
- PubMed: 12514135
- DOI: https://doi.org/10.1093/emboj/cdg025
- Primary Citation of Related Structures:
- PubMed Abstract:
The methylation of lysine residues of histones plays a pivotal role in the regulation of chromatin structure and gene expression. Here, we report two crystal structures of SET7/9, a histone methyltransferase (HMTase) that transfers methyl groups to Lys4 of histone H3, in complex with S-adenosyl-L-methionine (AdoMet) determined at 1.7 and 2.3 A resolution. The structures reveal an active site consisting of: (i) a binding pocket between the SET domain and a c-SET helix where an AdoMet molecule in an unusual conformation binds; (ii) a narrow substrate-specific channel that only unmethylated lysine residues can access; and (iii) a catalytic tyrosine residue. The methyl group of AdoMet is directed to the narrow channel where a substrate lysine enters from the opposite side. We demonstrate that SET7/9 can transfer two but not three methyl groups to unmodified Lys4 of H3 without substrate dissociation. The unusual features of the SET domain-containing HMTase discriminate between the un- and methylated lysine substrate, and the methylation sites for the histone H3 tail.
National Creative Research Initiative Center for Structural Biology and Department of Life Science, Pohang University of Science and Technology, Hyo-ja dong, San31, Pohang, KyungBook 790-784, South Korea.