TOG-tubulin binding specificity promotes microtubule dynamics and mitotic spindle formation

J Cell Biol. 2017 Jun 5;216(6):1641-1657. doi: 10.1083/jcb.201610090. Epub 2017 May 16.


XMAP215, CLASP, and Crescerin use arrayed tubulin-binding tumor overexpressed gene (TOG) domains to modulate microtubule dynamics. We hypothesized that TOGs have distinct architectures and tubulin-binding properties that underlie each family's ability to promote microtubule polymerization or pause. As a model, we investigated the pentameric TOG array of a Drosophila melanogaster XMAP215 member, Msps. We found that Msps TOGs have distinct architectures that bind either free or polymerized tubulin, and that a polarized array drives microtubule polymerization. An engineered TOG1-2-5 array fully supported Msps-dependent microtubule polymerase activity. Requisite for this activity was a TOG5-specific N-terminal HEAT repeat that engaged microtubule lattice-incorporated tubulin. TOG5-microtubule binding maintained mitotic spindle formation as deleting or mutating TOG5 compromised spindle architecture and increased the mitotic index. Mad2 knockdown released the spindle assembly checkpoint triggered when TOG5-microtubule binding was compromised, indicating that TOG5 is essential for spindle function. Our results reveal a TOG5-specific role in mitotic fidelity and support our hypothesis that architecturally distinct TOGs arranged in a sequence-specific order underlie TOG array microtubule regulator activity.

MeSH terms

  • Animals
  • Animals, Genetically Modified
  • Cell Line
  • Drosophila Proteins / chemistry
  • Drosophila Proteins / genetics
  • Drosophila Proteins / metabolism*
  • Drosophila melanogaster / genetics
  • Drosophila melanogaster / growth & development
  • Drosophila melanogaster / metabolism*
  • Mad2 Proteins / genetics
  • Mad2 Proteins / metabolism
  • Microtubule-Associated Proteins / chemistry
  • Microtubule-Associated Proteins / genetics
  • Microtubule-Associated Proteins / metabolism*
  • Microtubules / metabolism*
  • Mitosis*
  • Mitotic Index
  • Models, Molecular
  • Mutation
  • Protein Binding
  • Protein Interaction Domains and Motifs
  • Protein Multimerization
  • Spindle Apparatus / metabolism*
  • Time Factors
  • Transfection
  • Tubulin / metabolism*


  • Drosophila Proteins
  • Mad2 Proteins
  • Mad2 protein, Drosophila
  • Microtubule-Associated Proteins
  • Tubulin
  • msps protein, Drosophila

Associated data

  • PDB/2OF3