CLIP-170 tracks growing microtubule ends by dynamically recognizing composite EB1/tubulin-binding sites.
The microtubule cytoskeleton is crucial for the internal organization of eukaryotic cells. Several microtubule-associated proteins link microtubules to subcellular structures. A subclass of these proteins, the plus end-binding proteins (+TIPs), selectively binds to the growing plus ends of microtubules. Here, we reconstitute a vertebrate plus end tracking system composed of the most prominent +TIPs, end-binding protein 1 (EB1) and CLIP-170, in vitro and dissect their end-tracking mechanism. We find that EB1 autonomously recognizes specific binding sites present at growing microtubule ends. In contrast, CLIP-170 does not end-track by itself but requires EB1. CLIP-170 recognizes and turns over rapidly on composite binding sites constituted by end-accumulated EB1 and tyrosinated alpha-tubulin. In contrast to its fission yeast orthologue Tip1, dynamic end tracking of CLIP-170 does not require the activity of a molecular motor. Our results demonstrate evolutionary diversity of the plus end recognition mechanism of CLIP-170 family members, whereas the autonomous end-tracking mechanism of EB family members is conserved.
Bieling
Peter
P
European Molecular Biology Laboratory, Cell Biology and Biophysics Unit, 69117 Heidelberg, Germany.
Kandels-Lewis
Stefanie
S
Telley
Ivo A
IA
van Dijk
Juliette
J
Janke
Carsten
C
Surrey
Thomas
T
D000818:Animals; D001665:Binding Sites; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism* / Q000648:ultrastructure*; D008954:Models, Biological; D009363:Neoplasm Proteins / Q000378:metabolism*; D014404:Tubulin / Q000378:metabolism*; D014982:Xenopus laevis
C405804:EB1 microtubule binding proteins; D008869:Microtubule-Associated Proteins; D009363:Neoplasm Proteins; D014404:Tubulin; C076744:cytoplasmic linker protein 170