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CK2-dependent phosphorylation of the E2 ubiquitin conjugating enzyme UBC3B induces its interaction with beta-TrCP and enhances beta-catenin degradation.

Protein kinase CK2 is a ubiquitous and pleiotropic Ser/Thr protein kinase involved in cell growth and transformation. Here we report the identification by yeast interaction trap of a CK2 interacting protein, UBC3B, which is highly homologous to the E2 ubiquitin conjugating enzyme UBC3/CDC34. UBC3B complements the yeast cdc34-2 cell cycle arrest mutant in S. cerevisiae and transfers ubiquitin to a target substrate in vitro. UBC3B is specifically phosphorylated by CK2 in vitro and in vivo. We mapped by deletions and site directed mutagenesis the phosphorylation site to a serine residue within the C-terminal domain in position 233 of UBC3B and in the corresponding serine residue of UBC3. Following CK2-dependent phosphorylation both UBC3B and UBC3 bind to the F-box protein beta-TrCP, the substrate recognition subunit of an SCF (Skp1, Cul1, F-box) ubiquitin ligase. Furthermore, we observed that co-transfection of CK2alpha' together with UBC3B, but not with UBC3DeltaC, enhances the degradation of beta-catenin. Taken together these data suggest that CK2-dependent phosphorylation of UBC3 and UBC3B functions by regulating beta-TrCP substrate recognition.

Pubmed ID: 12037680


  • Semplici F
  • Meggio F
  • Pinna LA
  • Oliviero S



Publication Data

June 6, 2002

Associated Grants


Mesh Terms

  • Amino Acid Sequence
  • Anaphase-Promoting Complex-Cyclosome
  • Animals
  • Casein Kinase II
  • Cells, Cultured
  • Chloramphenicol O-Acetyltransferase
  • Cloning, Molecular
  • Cytoskeletal Proteins
  • DNA Primers
  • GTP-Binding Proteins
  • Gene Library
  • Genetic Complementation Test
  • Glutathione Transferase
  • Humans
  • Ligases
  • Mice
  • Molecular Sequence Data
  • Phosphorylation
  • Plasmids
  • Polymerase Chain Reaction
  • Precipitin Tests
  • Promoter Regions, Genetic
  • Protein-Serine-Threonine Kinases
  • Saccharomyces cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Sequence Homology, Amino Acid
  • Trans-Activators
  • Ubiquitin
  • Ubiquitin-Conjugating Enzymes
  • Ubiquitin-Protein Ligase Complexes
  • beta Catenin
  • beta-Transducin Repeat-Containing Proteins