DCPS Inhibitors (Sprint Bioscience)

The RNA decapping scavenger protein, DcpS, has recently been identified as a dependency in acute myeloid leukemia (AML). 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 DcpS modulation. Considering this strong DcpS dependence in AML cell lines, we explored PROTAC-mediated degradation as an alternative strategy to modulate DcpS activity. Herein, we report the development of JCS-1, a PROTAC exhibiting effective degradation of DcpS at nanomolar concentrations. JCS-1 non-covalently binds DcpS with a RG3039-based warhead and recruits the E3 ligase VHL, which induces potent, rapid, and sustained DcpS degradation in several AML cell lines. JCS-1 serves as a chemical biology tool to interrogate DcpS degradation and associated changes in RNA processes in different cellular contexts, which may be an attractive strategy for the treatment of AML and other DcpS-dependent genetic disorders.

The m7G cap is a unique nucleotide structure at the 5′‐end of all eukaryotic mRNAs. The cap specifically interacts with numerous cellular proteins and participates in biological processes that are essential for cell growth and function. To provide small molecular probes to study important cap‐recognizing proteins, we synthesized m7G nucleotides labeled with fluorescent tags via the terminal phosph(on)ate group and studied how their emission properties changed upon protein binding or enzymatic cleavage. Only the pyrene‐labeled compounds behaved as sensitive turn‐on probes. A pyrene‐labeled m7GTP analogue showed up to eightfold enhanced fluorescence emission upon binding to eukaryotic translation initiation factor 4E (eIF4E) and over 30‐fold enhancement upon cleavage by decapping scavenger (DcpS) enzyme. These observations served as the basis for developing binding‐ and hydrolytic‐activity assays. The assay utility was validated with previously characterized libraries of eIF4E ligands and DcpS inhibitors. The DcpS assay was also applied to study hydrolytic activity and inhibition of endogenous enzyme in cytoplasmic extracts from HeLa and HEK cells.