Matrimony Inhibits Polo Kinase

Suspended animation is something we only associate with Sci Fi programs,
but something remarkably similar actually occurs in unfertilized egg
cells,
in the ovaries of animals as different as humans and fruit flies. In an
article published online this week in the open-access journal PLoS
Biology,
researchers from the Stowers Institute describe the two proteins that
provide "Sleeping Beauty's Kiss" to the long-dormant egg cells.



Unlike sperm, which are generated over the course of a man's life, a girl
is born with all the egg cells she will ever produce. The special cell
division that creates sex cells (sperm and eggs) is called meiosis. During
egg production, meiosis is paused part of the way through-a pause that,
in humans, can last decades. Researchers in Scott Hawley's lab at the
Stowers Institute investigated the mechanism that brings eggs out of the
paused state, using the fruit fly Drosophila as a model.



Youbin Xiang and colleagues identified two proteins crucial in controlling
the pause in meiotic division. One protein, Polo kinase, is an enzyme that
restarts the process of meiosis. However, it takes several days for enough
Polo to build up. In the interim, a second protein called Matrimony binds
to Polo and prevents it from working. Matrimony allows the egg cell to
increase the amount of Polo until it is sufficient to force the cell
through to
the end of meiosis.



One question that arises from this work is just what destroys Matrimony at
the crucial point. The paper suggests that this may be a threshold
concentration of Polo, or else another, unidentified protein that targets
Matrimony. As Polo kinase is strongly expressed in many types of tumor
cells, identifying a specific inhibitor for this protein, such as
Matrimony, may aid the development of drugs for treating cancer. The work
by Xiang
et al. may also have long-term implications for humans, as understanding
the process by which eggs are matured and released could have profound
implications for treating infertility.


Citation: Xiang Y, Takeo S, Florens L, Hughes SE, Huo LJ, et al. (2007)
The inhibition of Polo kinase by Matrimony maintains G2 arrest in the
meiotic
cell cycle. PLoS Biol 5(12):e323. doi:10.1371/journal.pbio.0050323

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