Targeted protein degradation of the CPSF complex by benzoxaboroles through sumoylation

Benzoxaboroles (BoBs) feature a boron-heterocyclic core and are an important innovation in the development of drugs against a range of pathogens and other pathologies. A broad spectrum of pharmacology is associated with chemically diverse BoB derivatives and includes multiple modes-of-action (MoA) and targets. However, a consensus MoA for BoBs targeting evolutionarily diverse protozoan pathogens has emerged with the identification of CPSF3/CPSF73 in the CPSF complex in both apicomplexan and kinetoplastida parasites. Here we establish a functional connection between protein sumoylation and the boron-heterocyclic scaffold shared by all BoBs using comprehensive genetic screens in Trypanosoma brucei. There is a rapid temporal and spatial shift in global protein sumoylation following BoB exposure and members of the CPSF complex are specifically destabilised in a SUMO and proteosome-dependent manner. Finally, we find rapid decrease in bulk mRNA levels, consistent with the role of CPSF3 in mRNA maturation. We propose that a combination of direct inhibition coupled with targeted degradation of CPSF3 underpins the specificity of BoBs against trypanosomatids.