Originally published as Genetics Published Articles Ahead of Print on July 29, 2007.

Genetics, Vol. 177, 267-280, September 2007, Copyright © 2007
doi:10.1534/genetics.107.076091

Misregulation of the Kinesin-like Protein Subito Induces Meiotic Spindle Formation in the Absence of Chromosomes and Centrosomes

Waksman Institute and Department of Genetics, Rutgers, the State University of New Jersey, Piscataway, New Jersey 08854-8020

1 Corresponding author: Waksman Institute, Rutgers University, 190 Frelinghuysen Road, Piscataway, NJ 08854.
E-mail: mckim{at}rci.rutgers.edu

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.


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C. Wu, V. Singaram, and K. S. McKim
mei-38 Is Required for Chromosome Segregation During Meiosis in Drosophila Females
Genetics, September 1, 2008; 180(1): 61 - 72.
[Abstract] [Full Text] [PDF]