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J. Cell Biol.,
Volume 143, Number 6, December 14, 1998 1635-1646


* Cell Biology of Development and Differentiation Group and An emerging family of kinases related to the
Drosophila Aurora and budding yeast Ipl1 proteins has
been implicated in chromosome segregation and mitotic spindle formation in a number of organisms. Unlike other Aurora/Ipl1-related kinases, the Caenorhabditis elegans orthologue, AIR-2, is associated with
meiotic and mitotic chromosomes. AIR-2 is initially
localized to the chromosomes of the most mature prophase I-arrested oocyte residing next to the spermatheca. This localization is dependent on the presence
of sperm in the spermatheca. After fertilization, AIR-2
remains associated with chromosomes during each meiotic division. However, during both meiotic anaphases, AIR-2 is present between the separating chromosomes.
AIR-2 also remains associated with both extruded
polar bodies. In the embryo, AIR-2 is found on
metaphase chromosomes, moves to midbody microtubules at anaphase, and then persists at the cytokinesis
remnant. Disruption of AIR-2 expression by RNA-
mediated interference produces entire broods of one-cell embryos that have executed multiple cell cycles in
the complete absence of cytokinesis. The embryos accumulate large amounts of DNA and microtubule asters. Polar bodies are not extruded, but remain in the
embryo where they continue to replicate. The cytokinesis defect appears to be late in the cell cycle because
transient cleavage furrows initiate at the proper location, but regress before the division is complete. Additionally, staining with a marker of midbody microtubules revealed that at least some of the components of
the midbody are not well localized in the absence of
AIR-2 activity. Our results suggest that during each
meiotic and mitotic division, AIR-2 may coordinate the
congression of metaphase chromosomes with the subsequent events of polar body extrusion and cytokinesis.
Developmental Signal Transduction Group, ABL-Basic
Research Program, NCI-Frederick Cancer Research and Development Center, Frederick, Maryland 21702
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