Cell Biology

NE-ER Shape Shifting

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Science  26 Sep 2008:
Vol. 321, Issue 5897, pp. 1743
DOI: 10.1126/science.321.5897.1743a

Mitosis in metazoans involves the wholesale disruption of normal cellular architecture to allow for successful partitioning of cellular components to each daughter cell. During most of the cell cycle, the nucleus is surrounded by a double-membraned nuclear envelope (NE) that is contiguous with the endoplasmic reticulum (ER), an intracellular labyrinth of interconnected tubules and sheets. Anderson and Hetzer have examined the processes involved in the dramatic rearrangements of the NE and ER at the end of mitosis. The NE is disassembled at the beginning of mitosis and, after the partitioning of chromosomes, must be reassembled to form two daughter cells complete with their own NE-enclosed nuclei. By quantifying images produced using time lapse microscopy, the authors were able to observe the recruitment of ER tubules to chromatin, which went on, within ∼12 min, to produce membrane-enclosed daughter nuclei capable of performing nuclear import. Increasing the expression of ER tubule-promoting proteins interfered with the formation of new nuclei, whereas reducing their expression sped up the process, which may suggest that it is the transition of ER from tubules to sheets that limits NE assembly and nuclear expansion. Thus, ER architectural proteins play a key role in nuclear reconstruction and NE assembly after mitosis. — SMH

J. Cell Biol. 182, 911 (2008).

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