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Mammalian end binding proteins control persistent microtubule growth
Correspondence to Anna Akhmanova: a.akhmanova{at}erasmusmc.nl
End binding proteins (EBs) are highly conserved core components of microtubule plus-end tracking protein networks. Here we investigated the roles of the three mammalian EBs in controlling microtubule dynamics and analyzed the domains involved. Protein depletion and rescue experiments showed that EB1 and EB3, but not EB2, promote persistent microtubule growth by suppressing catastrophes. Furthermore, we demonstrated in vitro and in cells that the EB plus-end tracking behavior depends on the calponin homology domain but does not require dimer formation. In contrast, dimerization is necessary for the EB anti-catastrophe activity in cells; this explains why the EB1 dimerization domain, which disrupts native EB dimers, exhibits a dominant-negative effect. When microtubule dynamics is reconstituted with purified tubulin, EBs promote rather than inhibit catastrophes, suggesting that in cells EBs prevent catastrophes by counteracting other microtubule regulators. This probably occurs through their action on microtubule ends, because catastrophe suppression does not require the EB domains needed for binding to known EB partners.
Y. Komarova's present address is Department of Pharmacology, University of Illinois College of Medicine, Chicago, IL 60612.
J.M. Schober's present address is Southern Illinois University School of Pharmacy, Edwardsville, IL 62026.
S. Honnappa's present address is Novartis Pharma AG, CH-4000 Basel, Switzerland.
G.G. Borisy's present address is Marine Biological Laboratory, 7MBL Street, Woods Hole, MA 02543.
Abbreviations used in this paper: CH, calponin homology; DIC, differential interference contrast; EB, end binding protein; HA, hemagglutinin; IP, immunoprecipitation; MT, microtubule; +TIPs, microtubule plus-end tracking proteins; TIRFM, total internal reflection fluorescence microscopy.
© 2009 Komarova et al.
This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.jcb.org/misc/terms.shtml). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 3.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/3.0/).
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