Forgot Password

If you have forgotten your password you can enter your email here and get a temporary password sent to your email.

Erythropoietin receptors associate with a ubiquitin ligase, p33RUL, and require its activity for erythropoietin-induced proliferation.

The proliferation and survival of hematopoietic cells is strictly regulated by cytokine growth factors that act through receptors of the Type I cytokine receptor family, including erythropoietin (Epo) and its receptor, EpoR. Mitogenic signaling by these receptors depends on activation of Jak tyrosine kinases. However, other required components of this pathway have not been fully identified. In a screen for proteins that interact with EpoR and Jak2, we identified a novel member of the U-box family of ubiquitin ligases. This receptor-associated ubiquitin ligase, RUL, co-precipitated with EpoR from mammalian cells and mediated ubiquitination of EpoR. Also, endogenously expressed RUL was rapidly and transiently phosphorylated on serine after cytokine treatment of factor-dependent hematopoietic cells. Expression of ubiquitin ligase-deficient mutants of RUL inhibited Epo-induced expression of c-myc and bcl-2, two immediate-early genes normally associated with Epo-induced cell growth. Consistent with that finding, expression of mutant RUL also inhibited Epo-dependent proliferation and survival of factor-dependent cells. Together, these observations suggest that RUL is a required component of mitogenic signaling by EpoR. We also show that RUL is phosphorylated in response to growth factors that act through non-cytokine receptors, suggesting that RUL may function as a common regulator of mitogenesis.

Pubmed ID: 12746455


  • Friedman AD
  • Nimbalkar D
  • Quelle FW


The Journal of biological chemistry

Publication Data

July 18, 2003

Associated Grants

  • Agency: NIDDK NIH HHS, Id: DK25295

Mesh Terms

  • Amino Acid Sequence
  • Animals
  • COS Cells
  • Cell Division
  • Cell Line
  • Cloning, Molecular
  • Erythropoietin
  • Humans
  • In Vitro Techniques
  • Ligases
  • Molecular Sequence Data
  • Mutagenesis
  • Phosphorylation
  • Receptors, Erythropoietin
  • Recombinant Proteins
  • Sequence Homology, Amino Acid
  • Ubiquitin