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E1-L2 activates both ubiquitin and FAT10.

Ubiquitination is catalyzed by a cascade of enzymes consisting of E1, E2, and E3. We report here the identification of an E1-like protein, termed E1-L2, that activates both ubiquitin and another ubiquitin-like protein, FAT10. Interestingly, E1-L2 can transfer ubiquitin to Ubc5 and Ubc13, but not Ubc3 and E2-25K, suggesting that E1-L2 may be specialized in a subset of ubiquitination reactions. E1-L2 forms a thioester with FAT10 in vitro, and this reaction requires the active-site cysteine of E1-L2 and the C-terminal diglycine motif of FAT10. Furthermore, endogenous FAT10 forms a thioester with E1-L2 in cells stimulated with tumor necrosis factor-alpha (TNFalpha) and interferon-gamma (IFNgamma), which induce FAT10 expression. Silencing of E1-L2 expression by RNAi blocks the formation of FAT10 conjugates in cells. Deletion of E1-L2 in mice caused embryonic lethality, suggesting that E1-L2 plays an important role in embryogenesis.

Pubmed ID: 17889673


  • Chiu YH
  • Sun Q
  • Chen ZJ


Molecular cell

Publication Data

September 21, 2007

Associated Grants


Mesh Terms

  • Amino Acid Sequence
  • Animals
  • Embryo Loss
  • Embryonic Development
  • Gene Deletion
  • HeLa Cells
  • Humans
  • Mice
  • Molecular Sequence Data
  • Sulfhydryl Compounds
  • Ubiquitin-Activating Enzymes
  • Ubiquitin-Conjugating Enzymes
  • Ubiquitins