Targeted Degradation of mRNA Decapping Enzyme DcpS by a VHL-Recruiting PROTAC

The RNA decapping scavenger, DcpS, has recently been identified as a dependency in acute myeloid leukemia. The potent DcpS inhibitor RG3039 attenuates AML cell viability, and shRNA knockdown of DcpS is also antiproliferative. Importantly, DcpS was found to be non-essential in normal human hematopoietic cells, which opens a therapeutic window for AML treatment by modulation of DcpS. Considering this strong dependence of AML cell lines on DcpS, we wanted to explore PROTAC-mediated degradation as an alternative strategy to modulate DcpS activity. Herein, we report the development of JCS-1, the first PROTAC capable of degrading an mRNA-decapping enzyme. JCS-1 non-covalently binds DcpS with an RG3039-based warhead and recruits the E3 ligase VHL, which induces potent, rapid, and sustained DcpS degradation in several AML cell lines. JCS-1 will serve as a chemical biology tool to interrogate DcpS function in different cellular contexts and may be an applicable strategy for the treatment of AML and other DcpS-dependent genetic disorders. Overall design: RNA isolated from MOLM-14 cells treated with JCS-1, JCS-2, or RG3039 for 6 hours, and +/- s4U was subjected to oxidative-nucleophilic-aromatic-substitution chemistry. Sequencing libraries were prepared from all RNA