This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Epigenetic gene silencing in eukaryotes is regulated in part by lysine methylation of the core histone proteins. While histone lysine methylation is known to control gene expression through the recruitment of modification-specific effector proteins, it remains unknown whether nonhistone chromatin proteins are targets for similar modification-recognition systems. Here we show that the histone H3 methyltransferase G9a contains a conserved methylation motif with marked sequence similarity to H3 itself. As with methylation of H3 lysine 9, autocatalytic G9a methylation is necessary and sufficient to mediate in vivo interaction with the epigenetic regulator heterochromatin protein 1 (HP1), and this methyl-dependent interaction can be reversed by adjacent G9a phosphorylation. NMR analysis indicates that the HP1 chromodomain recognizes methyl-G9a through a binding mode similar to that used in recognition of methyl-H3K9, demonstrating that the chromodomain functions as a generalized methyl-lysine binding module. These data reveal histone-like modification cassettes - or """"""""histone mimics"""""""" - as a distinct class of nonhistone methylation targets and directly extend the principles of the histone code to the regulation of nonhistone proteins. A manuscript describing this work was published: Methylation of a histone mimic within the histone methyltransferase G9a regulates protein complex assembly. Sampath SC, Marazzi I, Yap KL, Sampath SC, Krutchinsky AN, Mecklenbr?uker I, Viale A, Rudensky E, Zhou MM, Chait BT, Tarakhovsky A. Mol Cell. 2007 Aug 17;27(4):596-608 We are currently investigating a series of other nonhistone methylation targets.
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