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  • The EMBO Journal (2002) 21, 355 - 364
  • doi:10.1093/emboj/21.3.355

Identification of a ubiquitin–protein ligase subunit within the CCR4–NOT transcription repressor complex

Thomas K. Albert1, Hiroyuki Hanzawa2,3, Yvonne I.A. Legtenberg1, Marjolein J. de Ruwe1, Fiona A.J. van den Heuvel4, Martine A. Collart5, Rolf Boelens2 and H.Th.Marc Timmers1

  1. Laboratory for Physiological Chemistry, University Medical Center, 3508 AB Utrecht, The Netherlands
  2. Bijvoet Center for Biomolecular Research, Utrecht University, 3584 CH Utrecht, The Netherlands
  3. Present address: Biomedical Research Laboratories, Sankyo Co. Ltd, 2-58, Hiromachi 1-chome Shinagawa-ku, Tokyo 140-8710, Japan
  4. Present address: Department of Gynaecology, University Hospital Groningen, 9700 RB Groningen, The Netherlands
  5. Department of Medical Biochemistry, CMU, University of Geneva, 1211 Geneva 4, Switzerland

Correspondence to:

H.Th.Marc Timmers, E-mail: H.T.M.Timmers@med.uu.nl

Received 7 September 2001; Accepted 26 November 2001; Revised 22 November 2001

The RING finger protein CNOT4 is a component of the CCR4–NOT complex. This complex is implicated in repression of RNA polymerase II transcription. Here we demonstrate that CNOT4 functions as a ubiquitin–protein ligase (E3). We show that the unique C4C4 RING domain of CNOT4 interacts with a subset of ubiquitin-conjugating enzymes (E2s). Using NMR spectroscopy, we detail the interaction of CNOT4 with UbcH5B and characterize RING residues that are critical for this interaction. CNOT4 acts as a potent E3 ligase in vitro. Mutations that destabilize the E2–E3 interface abolish this activity. Based on these results, we present a model of how E3 ligase function within the CCR4–NOT complex relates to transcriptional regulation.

  • Keywords:

    • CCR4–NOT complex,
    • RING finger,
    • TFIID,
    • transcription regulation,
    • ubiquitin–protein ligase