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CLASPing microtubules to the membrane

The Journal of Cell Biology
The Rockefeller University Press
Publication Date
DOI: 10.1083/jcb.1983iti3
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JCB_1983iti.indd In This Issue JCB • VOLUME 198 • NUMBER 3 • 2012266 Text by Mitch Leslie [email protected] Fungal pores feel the pull S teinberg et al. report that fungi use motor proteins to distribute their nuclear pores around the nuclear envelope. In animal cells, the nuclear lamina holds the nuclear pores in place, en- suring that they are evenly spaced. The lamina prevents nuclear pores from clustering, promoting import of cargoes through the pores and help- ing to organize the chromosomes, which are tethered to the pores. But fungi have no lamin genes, suggest- ing that they rely on a different mechanism to position their pores. Steinberg et al. found that fungal cells are constantly adjust- ing the locations of their nuclear pores. In the pathogenic fungus Ustilago maydis, the motor proteins kinesin-1 and dynein slide the pores around on microtubules. In budding yeast, by contrast, pore movements required the actin cytoskeleton, suggesting that myosin motors are providing the muscle power. The team also determined what happened if cells couldn’t rearrange their pores. The structures clumped in U. maydis cells lacking kinesin-1 and dynein. Transport of cargoes into and out of the nucleus slowed in cells missing either or both of the mo- tor proteins. When a cell moves its nuclear pores, it also moves its chromosomes. Blocking these movements caused chromo- somes to gather at the edge of the nucleus, usually near the pore clusters. This could explain why impeding pore movement in- hibits nuclear transport. Misplaced chromosomes might ob- struct cargoes traveling into and out of the nucleus. Steinberg, G., et al. 2012. J. Cell Biol. jcb.201201087. Chaperones team up twice T he chaperone Hsp70 lives up to its name, guiding its partner Hsp100 into position in two different situations, Winkler et al. reveal. Stress can spur proteins to misfold and clump. Hsp70 and Hsp100 enable yeast, bacteria, and

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