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Ubc9 sumoylation regulates SUMO target discrimination.

Posttranslational modification with small ubiquitin-related modifier, SUMO, is a widespread mechanism for rapid and reversible changes in protein function. Considering the large number of known targets, the number of enzymes involved in modification seems surprisingly low: a single E1, a single E2, and a few distinct E3 ligases. Here we show that autosumoylation of the mammalian E2-conjugating enzyme Ubc9 at Lys14 regulates target discrimination. While not altering its activity toward HDAC4, E2-25K, PML, or TDG, sumoylation of Ubc9 impairs its activity on RanGAP1 and strongly activates sumoylation of the transcriptional regulator Sp100. Enhancement depends on a SUMO-interacting motif (SIM) in Sp100 that creates an additional interface with the SUMO conjugated to the E2, a mechanism distinct from Ubc9 approximately SUMO thioester recruitment. The crystal structure of sumoylated Ubc9 demonstrates how the newly created binding interface can provide a gain in affinity otherwise provided by E3 ligases.

Pubmed ID: 18691969


  • Knipscheer P
  • Flotho A
  • Klug H
  • Olsen JV
  • van Dijk WJ
  • Fish A
  • Johnson ES
  • Mann M
  • Sixma TK
  • Pichler A


Molecular cell

Publication Data

August 8, 2008

Associated Grants


Mesh Terms

  • Amino Acid Motifs
  • Amino Acid Sequence
  • Autoantigens
  • Crystallography, X-Ray
  • Esters
  • HeLa Cells
  • Humans
  • Models, Molecular
  • Molecular Sequence Data
  • Protein Structure, Secondary
  • Saccharomyces cerevisiae
  • Small Ubiquitin-Related Modifier Proteins
  • Substrate Specificity
  • Ubiquitin-Conjugating Enzymes