Accepted_test

Nucleoporin Elys, the constituent of nuclear pore complexes, is a key factor determining their reassembly upon mitotic exit in multicellular organisms. In mammals, Xenopus and nematode, a fraction of Elys is localized on kinetochores during mitosis. Accordingly, depletion of Elys in these organisms results in mitotic defects and in the delay of cell cycle progression. However, Elys was shown to be absent on kinetochores during mitosis in Drosophila. Therefore, the question arises whether Elys depletion affects cell cycle progression in Drosophila cells.

We confirmed that Elys does not localize at kinetochores during mitosis in Drosophila by immunostaining of S2 cells with anti-Elys, anti-α-tubulin and anti-CenpA antibodies (the latter reveal the centromeres). Next, we performed flow cytometry analysis of cell cycle progression in control S2 cells and in S2 cells with Elys knockdown which was achieved by RNA-interference technique. We found only minor changes (if any) in cell cycle progression upon Elys knockdown in S2 cells. Our results indicate that, unlike in other organisms, in Drosophila S2 cells Elys does not stay at kinetochores during mitosis and its depletion does not lead to the disturbance of cell cycle progression. In other words, there is a clear correlation between Elys presence or absence on kinetochores in the organisms and abnormal or normal mitosis upon Elys depletion in these organisms. We, therefore, suggest that Drosophila Elys does not affect mitosis because it is not bound with kinetochores in this organism.