In the model proposed by [17], (a) rare events where IBM1 fails to remove H3K9me2 leads to (b) recruitment of CMT3 and methylation of CHG sites. (c) Methylation of CHG sites recruits KYP/SUVH4/5/6, di-methylating H3K9, and initiating a reinforcing loop with CMT3 and gbM. (d) and (e) CG sites are methylated by a yet undiscovered mechanism. (f) Subsequently, any CG site methylated will be maintained by MET1. (g) Over time, mCG spreads throughout the gene body.