3 Search Results

Cbl-b is a RING-type E3 ubiquitin ligase that is expressed in several immune cell lineages, where it negatively regulates the activity of immune cells. Cbl-b has specifically been identified as an attractive target for cancer immunotherapy due to its role in promoting an immunosuppressive tumor environment. A Cbl-b inhibitor, Nx-1607, is currently in phase I clinical trials for advanced solid tumor malignancies. Using a suite of biophysical and cellular assays, we confirm potent binding of C7683 (an analogue of Nx-1607) to the full-length Cbl-b and its N-terminal fragment containing the TKBD-LHR-RING domains. To further elucidate its mechanism of inhibition, we determinedmore » the co-crystal structure of Cbl-b with C7683, revealing the compound’s interaction with both the TKBD and LHR, but not the RING domain. Here, we provide structural insights into a novel mechanism of Cbl-b inhibition by a small-molecule inhibitor that locks the protein in an inactive conformation by acting as an intramolecular glue.« less

Protein arginine methyltransferases (PRMTs) regulate diverse biological processes and are increasingly being recognized for their potential as drug targets. Here we report the discovery of a potent, selective, and cell-active chemical probe for PRMT7. SGC3027 is a cell permeable prodrug, which in cells is converted to SGC8158, a potent, SAM-competitive PRMT7 inhibitor. Inhibition or knockout of cellular PRMT7 results in drastically reduced levels of arginine monomethylated HSP70 family stress-associated proteins. Structural and biochemical analyses reveal that PRMT7-driven in vitro methylation of HSP70 at R469 requires an ATP-bound, open conformation of HSP70. In cells, SGC3027 inhibits methylation of both constitutive andmore » inducible forms of HSP70, and leads to decreased tolerance for perturbations of proteostasis including heat shock and proteasome inhibitors. These results demonstrate a role for PRMT7 and arginine methylation in stress response.« less

PRDM9 is a PR domain containing protein which trimethylates histone 3 on lysine 4 and 36. Its normal expression is restricted to germ cells and attenuation of its activity results in altered meiotic gene transcription, impairment of double-stranded breaks and pairing between homologous chromosomes. There is growing evidence for a role of aberrant expression of PRDM9 in oncogenesis and genome instability. Here we report the discovery of MRK-740, a potent (IC₅₀: 80 ± 16 nM), selective and cell-active PRDM9 inhibitor (Chemical Probe). MRK-740 binds in the substrate-binding pocket, with unusually extensive interactions with the cofactor S-adenosylmethionine (SAM), conferring SAM-dependent substrate-competitivemore » inhibition. In cells, MRK-740 specifically and directly inhibits H3K4 methylation at endogenous PRDM9 target loci, whereas the closely related inactive control compound, MRK-740-NC, does not. The discovery of MRK-740 as a chemical probe for the PRDM subfamily of methyltransferases highlights the potential for exploiting SAM in targeting SAM-dependent methyltransferases.« less