Figure 1.
Gene silencing by DNA methylation. Gene expression is silenced in the early embryo by the activities of DNA methyltransferases (Dnmt) 3a and 3b which catalyse methylation of CpG dinucleotides do novo. This recruits methyl CpG binding protein (MeCP)-2 which in turn recruits the histone deacetylase (HDAC) / histone methyltransferase (HMT) complex which induce condensation of chromatin at the promoter. Methylation of CpG dinucleotides, and hence gene silencing, is maintained through mitotic cycles by Dnmt1 activity.