Nucleic Acids Research Advance Access originally published online on October 25, 2007
Nucleic Acids Research 2007 35(21):7313-7323; doi:10.1093/nar/gkm726
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Nucleic Acids Research, 2007, Vol. 35, No. 21 7313-7323
© 2007 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-com
Nucleic Acid Enzymes |
Automethylation of G9a and its implication in wider substrate specificity and HP1 binding
1New England Biolabs, 240 County Road, Ipswich, MA 01938-2723 and 2Department of Biological Chemistry, Gene Regulation Program, Jonsson Cancer Center, 10833 LeConte Ave., UCLA School of Medicine, Los Angeles, CA 90095-1737, USA
* To whom correspondence should be addressed. Tel: +1 978 380-7227; Fax: +1 978 921-1350; Email: pradhan{at}neb.com
Received July 19, 2007. Revised August 25, 2007. Accepted August 31, 2007.
Methylation of lysine residues on histones participates in transcriptional gene regulation. Lysine 9 methylation of histone H3 is a transcriptional repression signal, mediated by a family of SET domain containing AdoMet-dependent enzymes. G9a methyltransferase is a euchromatic histone H3 lysine 9 methyltransferase. Here, G9a is shown to methylate other cellular proteins, apart from histone H3, including automethylation of K239 residue. Automethylation of G9a did not impair or activate the enzymatic activity in vitro. The automethylation motif of G9a flanking target K239 (ARKT) has similarity with histone H3 lysine 9 regions (ARKS), and is identical to amino acids residues in EuHMT (ARKT) and mAM (ARKT). Under steady-state kinetic assay conditions, full-length G9a methylates peptides representing ARKS/T motif of H3, G9a, mAM and EuHMT efficiently. Automethylation of G9a at ARKT motif creates a binding site for HP1 class of protein and mutation of lysine in the motif impairs this binding. In COS-7 cells GFP fusion of the wild-type G9a co-localized with HP1
and HP1
isoforms whereas the G9a mutant with K239A displayed poor co-localization. Thus, apart from transcriptional repression and regulatory roles of lysine methylation, the non-histone protein methylation may create binding sites for cellular protein–protein interactions.
The authors wish it to be known that, in their opinion, the first two authors should be regarded as joint First Authors.