UBE2G1 governs the destruction of cereblon neomorphic substrates

Elife. 2018 Sep 20;7:e40958. doi: 10.7554/eLife.40958.

Abstract

The cereblon modulating agents (CMs) including lenalidomide, pomalidomide and CC-220 repurpose the Cul4-RBX1-DDB1-CRBN (CRL4CRBN) E3 ubiquitin ligase complex to induce the degradation of specific neomorphic substrates via polyubiquitination in conjunction with E2 ubiquitin-conjugating enzymes, which have until now remained elusive. Here we show that the ubiquitin-conjugating enzymes UBE2G1 and UBE2D3 cooperatively promote the K48-linked polyubiquitination of CRL4CRBN neomorphic substrates via a sequential ubiquitination mechanism. Blockade of UBE2G1 diminishes the ubiquitination and degradation of neomorphic substrates, and consequent antitumor activities elicited by all tested CMs. For example, UBE2G1 inactivation significantly attenuated the degradation of myeloma survival factors IKZF1 and IKZF3 induced by lenalidomide and pomalidomide, hence conferring drug resistance. UBE2G1-deficient myeloma cells, however, remained sensitive to a more potent IKZF1/3 degrader CC-220. Collectively, it will be of fundamental interest to explore if loss of UBE2G1 activity is linked to clinical resistance to drugs that hijack the CRL4CRBN to eliminate disease-driving proteins.

Keywords: PROTAC; biochemistry; cancer biology; cereblon; cereblon modulating agents; chemical biology; human; immunomodulatory drugs; ubiquitination.

MeSH terms

  • Adaptor Proteins, Signal Transducing
  • Amino Acid Sequence
  • Cell Line, Tumor
  • HEK293 Cells
  • Humans
  • Ikaros Transcription Factor / metabolism
  • Peptide Hydrolases / metabolism*
  • Proteolysis*
  • Substrate Specificity / drug effects
  • Thalidomide / analogs & derivatives
  • Thalidomide / pharmacology
  • Ubiquitin-Conjugating Enzymes / chemistry
  • Ubiquitin-Conjugating Enzymes / metabolism*
  • Ubiquitin-Protein Ligases / metabolism
  • Ubiquitination

Substances

  • Adaptor Proteins, Signal Transducing
  • CRBN protein, human
  • IKZF1 protein, human
  • Ikaros Transcription Factor
  • Thalidomide
  • pomalidomide
  • UBE2G1 protein, human
  • Ubiquitin-Conjugating Enzymes
  • Ubiquitin-Protein Ligases
  • Peptide Hydrolases
  • CRL4 protein, human

Grant support

No external funding was received for this work