Proximity-induced activation of human Cdc34 through heterologous dimerization

Stefan Gazdoiu, Kosj Yamoah, Kenneth Wu, Carlos R. Escalante, Inger Tappin, Vladimir Bermudez, Aneel K. Aggarwal, Jerard Hurwitz, Zhen Qiang Pan

Research output: Contribution to journalArticlepeer-review

33 Scopus citations


Cdc34 is an E2-conjugating enzyme required for catalyzing the polyubiquitination reaction mediated by the Skp1-CUL1-F-box (SCF) protein E3 ubiquiiin (Ub) ligase. Here, we show that the activity of human Cdc34 in the Ub-Ub ligation reaction was enhanced dramatically by SCF's core Ub ligase module, composed of a heterodimeric complex formed by the ROC1 RING finger protein and the CUL1 C terminus that contains a NeddS moiety covalently conjugated at K720. Unexpectedly, we found that N-terminal fusion of a GST moiety to human Cdc34 generated dimeric GST-Cdc34 that was constitutively active in supporting the assembly of K48-linked polyUb chains independently of SCF. Furthermore, fusion of a FK506-binding protein (FKBP) to the N terminus of human Cdc34 yielded FKBP-Cdc34 that was induced to form a dimer upon treatment with the chemical inducer AP20187. The AP20187-induced dimeric form of FKBP-Cdc34 was substantially more active than the monomer in catalyzing Ub-Ub ligation. Thus, juxtaposition of human Cdc34 activates its catalytic capability, suggesting that the SCF-mediated polyubiquitination reaction may require the conversion of Cdc34 from an inactive monomer to a highly active dimeric form.

Original languageEnglish
Pages (from-to)15053-15058
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number42
StatePublished - 18 Oct 2005


  • SCF
  • Ubiquitination


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