Abstract
Protein lysine methyltransferases (PKMTs) play crucial roles in normal physiology and disease processes. Profiling PKMT targets is an important but challenging task. With cancer-relevant G9a as a target, we have demonstrated success in developing S-adenosyl-L-methionine (SAM) analogues, particularly (E)-hex-2-en-5-ynyl SAM (Hey-SAM), as cofactors for engineered G9a. Hey-SAM analogue in combination with G9a Y1154A mutant modifies the same set of substrates as their native counterparts with remarkable efficiency. (E)-Hex-2-en-5-ynylated substrates undergo smooth click reaction with an azide-based probe. This approach is thus suitable for substrate characterization of G9a and expected to further serve as a starting point to evolve other PKMTs to utilize a similar set of cofactors.