Identification of the E3 ligase(s) recruited by 955 to degrade CDK9

PROTACs induce the degradation of target proteins by hijacking an E3 ligase. However, it is usually difficult to directly identify the E3 ligase recruited by a new E3 ligase ligand in a PROTAC using the co-immunoprecipitation method because the formation of the complex is transient and very dynamic. TurboID assay is a powerful proximity labeling method that can sensitively detect weak and transient protein-protein interactions by biotinylating proteins that interact with a bait protein fused with an engineered biotin ligase. Here, we adapted TurboID technology to identify and characterize the specific E3 ligase(s) recruited by 955, a potent piperlongumine (PL)-SNS-032 conjugated CDK9 PROTAC, to mediate CDK9 degradation.