Human EML4, a novel member of the EMAP family, is essential for microtubule formation
- Department of Hematopathology and Lymph Node Registry, Founded by the German Association of Pathologists at University of Kiel, Michaelisstr, 11, 24105 Kiel (Germany)
- Department of Immunology, University of Kiel (Germany)
- 1st Department of Medicine, University of Kiel (Germany)
- Department of Cell Biochemistry and Clinical Neurobiology, University of Hamburg (Germany)
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 [{sup 3}H]-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.
- OSTI ID:
- 20858033
- Journal Information:
- Experimental Cell Research, Vol. 312, Issue 17; Other Information: DOI: 10.1016/j.yexcr.2006.06.035; PII: S0014-4827(06)00240-0; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0014-4827
- Country of Publication:
- United States
- Language:
- English
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