Regulator of differentiation 1 (ROD1) binds to the amphipathic C-terminal peptide of thrombospondin-4 and is involved in its mitogenic activity

J Cell Physiol. 2009 Sep;220(3):672-9. doi: 10.1002/jcp.21817.


The matrix protein thrombospondin-4 has an acidic amphipathic C-terminal peptide (C21) which stimulates erythroid cell proliferation. Here we show that C21 stimulates red cell formation in anemic mice in vivo. In vitro experiments indicated that the peptide-mediated increase of erythroid colony formation in cultures of human CD34+ hematopoietic progenitor cells was possible only under continuous presence of erythropoietin. In the absence of this cytokine, C21 stimulated exclusively myeloid colony formation. Therefore, the peptide is not a specific erythroid differentiation factor. In fact, it is mitogenic in non-erythroid cells, such as skin fibroblasts and kidney epithelial cells. In erythroleukemic TF-1 cells, it actually decreased the production of the erythroid differentiation marker glycophorin A. C21-affinity chromatography revealed regulator of differentiation 1 (ROD1) as a major C21-binding protein. ROD1 is the hematopoietic cell paralog of polypyrimidine tract binding proteins (PTBs), RNA splice regulators which regulate differentiation by repressing tissue-specific exons. ROD1 binding to C21 was strongly inhibited by synthetic RNAs in the order poly A > poly U > poly G = poly C and was weakly inhibited by a synthetic phosphorylated peptide mimicking the C-terminal domain of RNA polymerase II. Cellular overexpression or knockdown experiments of ROD1 suggest a role for this protein in the mitogenic activity of C21. Since the nuclear proteins ROD1 and PTBs regulate differentiation at a posttranscriptional level and there is a fast nuclear uptake of C21, we put forward the idea that the peptide is internalized, goes to the nucleus and maintains cells in a proliferative state by supporting ROD1-mediated inhibition of differentiation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Active Transport, Cell Nucleus
  • Anemia / blood*
  • Anemia / chemically induced
  • Animals
  • Binding Sites
  • Cell Proliferation*
  • Cells, Cultured
  • Disease Models, Animal
  • Epithelial Cells / metabolism
  • Erythroid Precursor Cells / metabolism*
  • Erythropoiesis*
  • Erythropoietin / metabolism
  • Fibroblasts / metabolism
  • Glycophorins / metabolism
  • Humans
  • Kidney / metabolism
  • Leukemia, Erythroblastic, Acute / metabolism
  • Leukemia, Erythroblastic, Acute / pathology
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Peptide Fragments / chemistry
  • Peptide Fragments / metabolism*
  • Polypyrimidine Tract-Binding Protein / metabolism
  • Protein Structure, Tertiary
  • RNA Interference
  • RNA-Binding Proteins / genetics
  • RNA-Binding Proteins / metabolism*
  • Recombinant Proteins / metabolism
  • Skin / metabolism
  • Thrombospondins / chemistry
  • Thrombospondins / metabolism*
  • Time Factors
  • Transduction, Genetic
  • Zidovudine


  • Glycophorins
  • PTBP3 protein, human
  • Peptide Fragments
  • RNA-Binding Proteins
  • Recombinant Proteins
  • Thrombospondins
  • thrombospondin 4
  • Erythropoietin
  • Polypyrimidine Tract-Binding Protein
  • Zidovudine