Cell Biology

That's Torn It

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Science  01 Feb 2002:
Vol. 295, Issue 5556, pp. 767
DOI: 10.1126/science.295.5556.767c

At the beginning of mitosis, the cell's nucleus breaks down, releasing the condensed chromosomes to be arranged on the mitotic spindle for partitioning to daughter cells. Basic morphological evidence of this process is well established.

Now Beaudouin et al. have examined the process of nuclear envelope breakdown in real time in living cells, and Salina et al. examined the same process in synchronized cell cultures entering mitosis. They both observed the catastrophic “tearing” of the nuclear envelope at the onset of mitosis. This tearing process appears to be actively mediated by microtubules with the help of the molecular motor dynein. If microtubules are disrupted just before mitosis, envelope breakdown is inhibited. Dynein concentrates on the nuclear envelope before its breakdown, and interfering with dynein activity inhibits nuclear envelope breakdown. Fragments of nuclear envelope that remain attached to condensed chromosomes move toward the centrosomes along microtubules. Together the papers suggest a mechanical process by which biochemical processes involved in the breakdown of the nuclear envelope are enhanced to facilitate progression through mitosis. — SMH

Cell108, 83; 97 (2002).

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