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Characterization of a novel ubiquitin-conjugating enzyme that regulates beta1,4-galactosyltransferase-1 in embryonic stem cells.

In this study we identified a novel galactosyltransferase 1-associating protein (GTAP) by cDNA cloning from a murine embryonic cDNA library using the two-hybrid yeast system. GTAP is expressed in early embryonic tissues, as well as in adult tissues with active cell turnover, and belongs to the class III ubiquitin-conjugating (E2) enzyme family. Its COOH-terminal domain contains a consensus sequence for ubiquitin binding shared by all the ubiquitin-conjugating enzymes, whereas its NH(2)-terminal domain appears critical for the binding and internalization of cell surface galactosyltransferase 1 (GalT1) in embryonic stem cells through a monensin- and MG132-dependent pathway. We have found that GTAP regulates GalT1-associated, laminin-dependent embryonic cell adhesion and the formation of embryoid bodies. Thus, GTAP functions as an evolutionarily conserved E2 enzyme, which may participate in intercellular adhesion and embryonic development. Disclosure of potential conflicts of interest is found at the end of this article.

Pubmed ID: 18511602


  • Wassler MJ
  • Shur BD
  • Zhou W
  • Geng YJ


Stem cells (Dayton, Ohio)

Publication Data

August 14, 2008

Associated Grants

  • Agency: PHS HHS, Id: R01-D07120
  • Agency: NHLBI NIH HHS, Id: R01-HL69509

Mesh Terms

  • Amino Acid Sequence
  • Animals
  • Cell Adhesion
  • DNA, Complementary
  • Embryo Culture Techniques
  • Embryonic Stem Cells
  • Evolution, Molecular
  • Mice
  • Molecular Sequence Data
  • N-Acetyllactosamine Synthase
  • Protein Structure, Tertiary
  • Sequence Homology, Amino Acid
  • Tissue Distribution
  • Two-Hybrid System Techniques
  • Ubiquitin-Conjugating Enzymes