Single subunit degradation of WIZ, a lenalidomide- and pomalidomide dependent substrate of E3 ubiquitin ligase CRL4^(CRBN)
Immunomodulators (IMiDs) are an effective class of drugs used to treat blood cancers. IMiDs are believed to work by recruiting protein targets containing a β-hairpin motif for ubiquitination by E3 ubiquitin ligase complexes composed of cereblon (CRBN), Cullin-4a (CUL4a), DNA Damage Binding protein-1 (DDB1), and Ring Box-1 (RBX1). The ubiquitinated protein is subsequently degraded by the proteasome. By characterizing the repertoire of proteins that show an increased physical association with CRBN after IMiD treatment, we identified a novel IMiD substrate, Widely Interspaced Zinc Finger Motifs (WIZ). WIZ contains a C2H2 zinc finger domain, like several other substrates that were previously characterized. We demonstrate that IMiDs stabilize physical association of WIZ with CRBN, deplete WIZ steady state protein levels in a way that is dependent on E3 ligase activity, and enhance the rate of its degradation. Notably, proteins that assemble with WIZ are co-recruited to CRBN by IMiDs but are not degraded, illustrating the potential of targeted protein degradation to eliminate individual subunits of a protein complex. These findings suggest that systematic characterization of the full repertoire of proteins that are targeted for degradation by IMiD compounds will be required to better understand their biological effects.
Additional InformationThe copyright holder for this preprint is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under a CC-BY-ND 4.0 International license. bioRxiv preprint first posted online Apr. 2, 2019. Thanks to Rati Verma, Jennifer Mamrosh, Emily Blythe, Thang Nguyen, and David Sherman for scientific discussion. Thanks to Thang Nguyen for MM.1s CRBN KD and parental cell lines, and preparing samples in Fig. 2. H.H.Y was supported by NSF GRFP fellowship. R.J.D. was an investigator at the Howard Hughes Medical institute, and this work was supported by HHMI and a gift from Amgen.
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