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Human EML4, a novel member of the EMAP family, is essential for microtubule formation.

Human EML4 (EMAP-like protein 4) is a novel microtubule-associated WD-repeat protein of 120 kDa molecular weight, which is classified as belonging to the conserved family of EMAP-like proteins. Cosedimentation assays demonstrated that EML4 associates with in vitro polymerized microtubules. Correspondingly, immunofluorescence stainings and transient expression of EGFP-labeled EML4 revealed a complete colocalization of EML4 with the interphase microtubule array of HeLa cells. We present evidence that the amino-terminal portion of EML4 (amino acids 1-249) is essential for the association with microtubules. Immunoprecipitation experiments revealed that EML4 is hyperphosphorylated on serine/threonine residues during mitosis. In addition, immunofluorescence stainings demonstrated that hyperphosphorylated EML4 is associated with the mitotic spindle, suggesting that the function of EML4 is regulated by phosphorylation. siRNA-mediated knockdown of EML4 in HeLa cells led to a significant decrease in the number of cells. In no case mitotic figures could be observed in EML4 negative HeLa cells. Additionally, we observed a significant reduction of the proliferation rate and the uptake of radioactive [3H]-thymidine as a result of EML4 silencing. Most importantly, EML4 negative cells showed a completely modified microtubule network, indicating that EML4 is necessary for correct microtubule formation.

Pubmed ID: 16890222

Authors

  • Pollmann M
  • Parwaresch R
  • Adam-Klages S
  • Kruse ML
  • Buck F
  • Heidebrecht HJ

Journal

Experimental cell research

Publication Data

October 15, 2006

Associated Grants

None

Mesh Terms

  • Animals
  • Cell Cycle
  • Cell Cycle Proteins
  • Cell Line
  • Cell Line, Tumor
  • Cell Survival
  • Green Fluorescent Proteins
  • HeLa Cells
  • Humans
  • Immunoprecipitation
  • Mice
  • Mice, Inbred BALB C
  • Microtubule-Associated Proteins
  • Microtubules
  • Phosphorylation
  • RNA Interference
  • RNA, Small Interfering
  • Serine Endopeptidases
  • Transfection