The Mechanism And Biological Function Of Negative Regulation Of DNA Methylation By USP7

The faithful propagation of DNA methylation patterns during DNA replication requires a coordinated function of DNMT1 and its accessory protein UHRF1 and is critically required for maintaining the cellular identity and function.However,how DNA maintenance methylation is regulated remains poorly understood.In this study we show that deubiquitinase USP7 actually functions as a negative regulator for DNA methylation.Knockout of USP7 in either wild-type or DNMT3A/DNMT3 B double knockout cell lines results in globally increased levels of DNA methylation.Overexpression of the wild-type but not deubiquitinase-deficient USP7 led to decreased DNA methylation.We present evidence that USP7 suppresses the recruitment of DNMT1 to DNA replication foci and does so through 1)inhibiting the interaction between DNMT1 and UHRF1 and 2)deubiquitinating the ubiquitinated histone H3 and H2 B,which are catalyzed by UHRF1 and required for DNMT1 replication fork recruitment during DNA replication.We also demonstrate that the negatively regulation of DNA methylation by USP7 is evolutionarily conserved in mouse embryo development.Furthermore,we propose that the negative regulation of DNA methylation by USP7 plays roles in normal cellular growth and cell senescence.Our study thereby reveals for the first time that DNA maintenance methylation by DNMT1 is under a constitutively negative regulation and also provides novel insight into the mechanism of homeostatic regulation of DNA methylation.