HURP is part of a Ran-dependent complex involved in spindle formation.
BACKGROUND
GTP-loaded Ran induces the assembly of microtubules into aster-like and spindle-like structures in Xenopus egg extract. The microtubule-associated protein (MAP), TPX2, can mediate Ran's role in aster formation, but factors responsible for the transition from aster-like to spindle-like structures have not been described.


RESULTS
Here we identify a complex that is required for the conversion of aster-like to spindle-like structures. The complex consists of two characterized MAPs (TPX2, XMAP215), a plus end-directed motor (Eg5), a mitotic kinase (Aurora A), and HURP, a protein associated with hepatocellular carcinoma. Formation and function of the complex is dependent on Aurora A activity. HURP protein was further characterized and shown to bind microtubules and affect their organization both in vitro and in vivo. In egg extract, anti-HURP antibodies disrupt the formation of both Ran-dependent and chromatin and centrosome-induced spindles. HURP is also required for the proper formation and function of mitotic spindles in HeLa cells.


CONCLUSIONS
HURP is a new and essential component of the mitotic apparatus. HURP acts as part of a multicomponent complex that affects the growth or stability of spindle MTs and is required for spindle MT organization.
Koffa
Maria D
MD
EMBL, Heidelberg, Germany.
Casanova
Claudia M
CM
Santarella
Rachel
R
Köcher
Thomas
T
Wilm
Matthias
M
Mattaj
Iain W
IW
D000818:Animals; D064127:Aurora Kinases; D020090:Chromosome Segregation; D006367:HeLa Cells; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000502:physiology; D008870:Microtubules / Q000378:metabolism; D046912:Multiprotein Complexes; D009363:Neoplasm Proteins / Q000276:immunology / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism / Q000502:physiology; D008941:Spindle Apparatus / Q000378:metabolism*; D014981:Xenopus; D029867:Xenopus Proteins / Q000502:physiology; D020931:ran GTP-Binding Protein / Q000378:metabolism
C486738:CKAP5 protein, Xenopus; C465041:DLGAP5 protein, human; D008869:Microtubule-Associated Proteins; D046912:Multiprotein Complexes; D009363:Neoplasm Proteins; D029867:Xenopus Proteins; D064127:Aurora Kinases; D017346:Protein Serine-Threonine Kinases; D020931:ran GTP-Binding Protein