GSK-3484862 targets DNMT1 for degradation in cells

Maintenance of genomic methylation patterns at DNA replication forks by DNMT1 is the key to faithful mitotic inheritance. DNMT1 is often overexpressed in cancer cells and the DNA hypomethylating agents azacytidine and decitabine are currently used in the treatment of hematologic malignancies. However, the toxicity of these cytidine analogs and their ineffectiveness in treating solid tumors have limited wider clinical use. GSK-3484862 is a newly-developed, dicyanopyridine containing, non-nucleoside DNMT1-selective inhibitor with low cellular toxicity. Here, we show that GSK-3484862 targets DNMT1 for protein degradation in both cancer cell lines and murine embryonic stem cells (mESCs). DNMT1 depletion was rapid, taking effect within hours following GSK-3484862 treatment, leading to global hypomethylation. Inhibitor-induced DNMT1 degradation was proteasome-dependent, with no discernible loss of DNMT1 mRNA. In mESCs, GSK-3484862-induced Dnmt1 degradation requires Uhrf1, an accessory factor of Dnmt1 with E3 ubiquitin ligase activity. We also show that Dnmt1 depletion and DNA hypomethylation induced by the compound are reversible after its removal. Together, these results indicate that this DNMT1-selective degrader/inhibitor will be a valuable tool for dissecting both coordinated events linking DNA methylation to gene expression and identifying downstream effectors that ultimately regulate cellular response to altered DNA methylation patterns in a tissue/cell-specific manner. Highlights GSK-3484862 targets DNMT1 for protein degradation in a wide-range of cancer cell lines, without a decrease in DNMT1 mRNA levels DNMT1 depletion leads to a >50% loss of global DNA methylation in cells within 2-days of treatment with GSK-3484862 GSK-3484862-induced DNMT1 degradation is proteasome-dependent In mESCs, Uhrf1 is required for GSK-3484862 to induce Dnmt1 degradation