Cell Biology

Maintaining Distinctions

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Science  23 Jan 2004:
Vol. 303, Issue 5657, pp. 435
DOI: 10.1126/science.303.5657.435a

During mammalian cell division, single-copy organelles such as the Golgi apparatus must be partitioned, with a portion allocated to each daughter cell. At the onset of mitosis, the Golgi apparatus disassembles from a compact structure located next to the nucleus into small vesicles that appear as a dispersed cloud within the cytosol. It is also possible to induce Golgi disassembly experimentally by adding the drug brefeldin A, but in this case the Golgi membranes actually merge with the distributed network of membranes that constitute the endoplasmic reticulum (ER).

Pecot and Malhotra address a long-standing debate about whether the contents of Golgi-derived vesicles and of the ER mix during mitosis. The small molecule rapamycin enters into a tightly associated trimeric complex with two proteins, FKBP and FRAP, that do not by themselves interact. After joining FKBP to the Golgi enzyme sialyltransferase and FRAP to an ER-resident protein, the authors observed rapamycin-mediated colocalization of the latter with the former only when brefeldin A was added to dividing cells, demonstrating that (in a drug-free environment) the Golgi and the ER remain distinct compartments throughout mitosis. — SMH

Cell 116, 99 (2004).

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