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The conserved SOCS box motif in suppressors of cytokine signaling binds to elongins B and C and may couple bound proteins to proteasomal degradation.

The suppressors of cytokine signaling (SOCS) family of proteins act as intracellular inhibitors of several cytokine signal transduction pathways. Their expression is induced by cytokine activation of the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway and they act as a negative feedback loop by subsequently inhibiting the JAK/STAT pathway either by direct interaction with activated JAKs or with the receptors. These interactions are mediated at least in part by the SH2 domain of SOCS proteins but these proteins also contain a highly conserved C-terminal homology domain termed the SOCS box. Here we show that the SOCS box mediates interactions with elongins B and C, which in turn may couple SOCS proteins and their substrates to the proteasomal protein degradation pathway. Analogous to the family of F-box-containing proteins, it appears that the SOCS proteins may act as adaptor molecules that target activated cell signaling proteins to the protein degradation pathway.

Pubmed ID: 10051596


  • Zhang JG
  • Farley A
  • Nicholson SE
  • Willson TA
  • Zugaro LM
  • Simpson RJ
  • Moritz RL
  • Cary D
  • Richardson R
  • Hausmann G
  • Kile BT
  • Kile BJ
  • Kent SB
  • Alexander WS
  • Metcalf D
  • Hilton DJ
  • Nicola NA
  • Baca M


Proceedings of the National Academy of Sciences of the United States of America

Publication Data

March 2, 1999

Associated Grants

  • Agency: NCI NIH HHS, Id: CA-22556

Mesh Terms

  • Amino Acid Sequence
  • Animals
  • Binding Sites
  • Carrier Proteins
  • Cell Line
  • Cysteine Endopeptidases
  • Cytokines
  • Humans
  • Intracellular Signaling Peptides and Proteins
  • Mice
  • Models, Chemical
  • Molecular Sequence Data
  • Multienzyme Complexes
  • Proteasome Endopeptidase Complex
  • Protein-Tyrosine Kinases
  • Proteins
  • Recombinant Fusion Proteins
  • Recombinant Proteins
  • Repressor Proteins
  • Signal Transduction
  • Suppressor of Cytokine Signaling Proteins
  • Transcription Factors
  • Transfection
  • Tumor Cells, Cultured
  • src Homology Domains