Figure 7.

Regulation of MBD1-mediated repression by a competition between PIAS proteins and SETDB1. (A) The formation of the MBD1/SETDB1 repressive complex would be favoured in cells expressing low levels of PIAS1 or PIAS3. (B) PIAS1 and PIAS3 would compete more efficiently against SETDB1 if their expression is high. This would result in the conjugation of SUMO1 to MBD1 and a decrease of the repressive MBD1/SETDB1 complex. In order to achieve efficient expression of target genes, H3K9 methylation has to be removed from chromatin by either the cells undergoing a round of DNA replication or by some alternative mechanism.