Misregulation of the kinesin-like protein Subito induces meiotic spindle formation in the absence of chromosomes and centrosomes

Bipolar spindles assemble in the absence of centrosomes in the oocytes of many species. In Drosophila melanogaster oocytes, the chromosomes have been proposed to initiate spindle assembly by nucleating or capturing microtubules, although the mechanism is not understood. An important contributor to t...

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Bibliographic Details
Published in:	Genetics (Austin) Vol. 177; no. 1; pp. 267 - 280
Main Authors:	Jang, J.K, Rahman, T, Kober, V.S, Cesario, J, McKim, K.S
Format:	Journal Article
Language:	English
Published:	United States Genetics Soc America 01-09-2007 Genetics Society of America Copyright © 2007 by the Genetics Society of America
Subjects:	Animals Animals, Genetically Modified antiparallel microtubules Blotting, Western Cellular biology Centrosome - physiology Chromosomes Drosophila melanogaster Drosophila Proteins - genetics Drosophila Proteins - metabolism Female Fluorescent Antibody Technique Infertility Investigations kinensin Kinesin - genetics Kinesin - metabolism Male Meiosis meiotic spindle apparatus Metaphase microtubules Microtubules - physiology Motors Mutation oocytes Oocytes - cytology Oocytes - physiology Phenotype protein-protein interactions Proteins Spindle Apparatus - physiology spindle pole body Subito protein
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Summary:	Bipolar spindles assemble in the absence of centrosomes in the oocytes of many species. In Drosophila melanogaster oocytes, the chromosomes have been proposed to initiate spindle assembly by nucleating or capturing microtubules, although the mechanism is not understood. An important contributor to this process is Subito, which is a kinesin-6 protein that is required for bundling interpolar microtubules located within the central spindle at metaphase I. We have characterized the domains of Subito that regulate its activity and its specificity for antiparallel microtubules. This analysis has revealed that the C-terminal domain may interact independently with microtubules while the motor domain is required for maintaining the interaction with the antiparallel microtubules. Surprisingly, deletion of the N-terminal domain resulted in a Subito protein capable of promoting the assembly of bipolar spindles that do not include centrosomes or chromosomes. Bipolar acentrosomal spindle formation during meiosis in oocytes may be driven by the bundling of antiparallel microtubules. Furthermore, these experiments have revealed evidence of a nuclear- or chromosome-based signal that acts at a distance to activate Subito. Instead of the chromosomes directly capturing microtubules, signals released upon nuclear envelope breakdown may activate proteins like Subito, which in turn bundles together microtubules.
Bibliography:	http://www.genetics.org/ ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 Corresponding author: Waksman Institute, Rutgers University, 190 Frelinghuysen Road, Piscataway, NJ 08854. E-mail: mckim@rci.rutgers.edu Communicating editor: A. Villeneuve
ISSN:	0016-6731 1943-2631 1943-2631
DOI:	10.1534/genetics.107.076091