Abstract
Cell division is controlled through cooperation of different kinases. Of these, polo-like kinase 1 (Plk1) and p90 ribosomal S6 kinase 1 (RSK1) play key roles. Plk1 acts as a G(2)/M trigger, and RSK1 promotes G(1) progression. Although previous reports show that Plk1 is suppressed by RSK1 during meiosis in Xenopus oocytes, it is still not clear whether this is the case during mitosis or whether Plk1 counteracts the effects of RSK1. Few animal models are available for the study of controlled and transient cell cycle arrest. Here we show that encysted embryos (cysts) of the primitive crustacean Artemia are ideal for such research because they undergo complete cell cycle arrest when they enter diapause (a state of obligate dormancy). We found that Plk1 suppressed the activity of RSK1 during embryonic mitosis and that Plk1 was inhibited during embryonic diapause and mitotic arrest. In addition, studies on HeLa cells using Plk1 siRNA interference and overexpression showed that phosphorylation of RSK1 increased upon interference and decreased after overexpression, suggesting that Plk1 inhibits RSK1. Taken together, these findings provide insights into the regulation of Plk1 during cell division and Artemia diapause cyst formation and the correlation between the activity of Plk1 and RSK1.
Highlights
polo-like kinase 1 (Plk1) can be inhibited by ribosomal S6 kinase 1 (RSK1) during meiosis
Previous reports show that Plk1 is suppressed by RSK1 during meiosis in Xenopus oocytes, it is still not clear whether this is the case during mitosis or whether Plk1 counteracts the effects of RSK1
We found that Plk1 suppressed the activity of RSK1 during embryonic mitosis and that Plk1 was inhibited during embryonic diapause and mitotic arrest
Summary
Plk can be inhibited by RSK1 during meiosis. Results: Activities of members of the MEK-ERK-RSK1 signaling pathway increase when Plk is knocked down, and both of these pathways shut down during cell cycle arrest. Studies on HeLa cells using Plk siRNA interference and overexpression showed that phosphorylation of RSK1 increased upon interference and decreased after overexpression, suggesting that Plk inhibits RSK1. Taken together, these findings provide insights into the regulation of Plk during cell division and Artemia diapause cyst formation and the correlation between the activity of Plk and RSK1. Overexpression of Plk in HeLa cells resulted in decreased activation of RSK1 The interplay between these two molecules was controlled by the upstream MEK-ERK pathway and was not due to their common downstream substrate, Myt
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