Deciphering ubiquitin code using chemo-technologies and advanced proteomics
Atsuya Nishiyama, PhD
Division of Cancer Cell Biology, The Institute of Medical Science, The University of Tokyo
DNA methylation is an epigenetic chemical modification that plays an essential role in a variety of biological processes. In recent years, DNA methyltransferase inhibitors that induce DNA hypomethylation have become a promising tool in cancer therapy. 5-aza-2-deoxycytidine (5-aza-2-dC), a derivative of deoxycytidine, is incorporated into genomic DNA during DNA replication and traps DNMT1 in the genome by forming irreversible covalent bonds. DNMT1 is then removed from the cell by proteasome-dependent proteolysis. However, the molecular mechanism of DNA-DNMT1 cross-link repair remains unclear. Using a cell-free system derived from Xenopus egg extracts, we found that 5-aza-dCTP induces a high level of DNMT1 Sumoylation and activation of UHRF1 E3 ubiquitin ligase. Based on these data, we propose the central hypothesis that DNMT1 Sumoylation plays a critical role in regulating DNMT1-DNA cross-link repair. Our specific aims are outlined below:
- Identification and analysis of E3 SUMO ligase for DNMT1
- Identification and analysis of reader proteins of Sumoylated DNMT1
- Identification of novel substrates of UHRF1
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