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Hypoxic reaction to reactive oxygen

The Journal of Cell Biology
The Rockefeller University Press
Publication Date
DOI: 10.1083/jcb.1776iti3
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JCB_1776iti.indd IN THIS ISSUE • THE JOURNAL OF CELL BIOLOGY 945 Text by Nicole LeBrasseur [email protected] A stress-coping strategy of the ER is needed in every cell cycle, show Bicknell et al. (page 1017). The ER’s unfolded protein response (UPR), previously associated only with unusual or stressful conditions, is needed for the routine event of cytokinesis. The UPR is activated when the ER is overloaded with misfolded proteins. It increases ER capacity and helps reduce the load. But the authors wondered whether everyday ER fl uctuations might also tweak the UPR. One particularly taxing process, the group reasoned, is cell division. Sure enough, cytokinesis was slowed in budding yeast cells that lacked the UPR. The stalls required no additional stress; division was enough. No other mitotic stages were affected. The ER supports cytokinesis by making new phospholipids for the pinching process and as the fi rst stage of the secre- tory pathway, which provides necessary vesicles to the bud neck. Either of these cytokinetic duties might put enough strain on the ER to activate the UPR slightly. Artifi cially induced ER stress prevented yeast cells from completing cytokinesis. This blockade might stem from the ab- sence of the required secretory vesicles or phospholipids. Or it might be activated as a checkpoint, stalling division until the ER is in better shape. Unlike yeast, the mammalian UPR dampens translation, which stalls cells in G1 by limiting cyclin D1 levels. If pushed through this blockade, however, the cells might reveal a need for the UPR in break- ing apart mammalian daughter cells. Dynein’s spindly tr ip D ynein has fi nally found a partner with direc- tion. On page 1005, Griffis et al. identify a co- factor for the motor that seems to bring it to kinetochores and only kinetochores. With everything it has to do in the cell, dynein has many places to be. During mitosis, dynein is needed at kinetochores, whe

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