Promiscuous Binding of Microprotein Mozart1 to γ-Tubulin Complex Mediates Specific Subcellular Targeting to Control Microtubule Array Formation

Cell Rep. 2020 Jun 30;31(13):107836. doi: 10.1016/j.celrep.2020.107836.

Abstract

How γ-tubulin ring complex (γ-TuRC), a master template for microtubule nucleation, is spatially and temporally regulated for the assembly of new microtubule arrays remains unclear. Here, we report that an evolutionarily conserved microprotein, Mozart1 (Mzt1), regulates subcellular targeting and microtubule formation activity of γ-TuRC at different cell cycle stages. Crystal structures of protein complexes demonstrate that Mzt1 promiscuously interacts with the N-terminal domains of multiple γ-tubulin complex protein subunits in γ-TuRC via an intercalative binding mode. Genetic- and microscopy-based analyses show that promiscuous binding of Mzt1 in γ-TuRC controls specific subcellular localization of γ-TuRC to modulate microtubule nucleation and stabilization in fission yeast. Moreover, we find Mzt1-independent targeting of γ-TuRC to be crucial for mitotic spindle assembly, demonstrating the cell-cycle-dependent regulation and function of γ-TuRC. Our findings reveal a microprotein-mediated regulatory mechanism underlying microtubule cytoskeleton formation, whereby Mzt1 binding promiscuity confers localization specificity on the multi-protein complex γ-TuRC.

Keywords: Mozart1; microprotein; microtubule nucleation; γ-TuRC; γ-TuRC targeting.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Conserved Sequence
  • Evolution, Molecular*
  • Humans
  • Interphase
  • Microtubule-Associated Proteins / chemistry
  • Microtubule-Associated Proteins / metabolism*
  • Microtubule-Organizing Center / metabolism
  • Microtubules / metabolism*
  • Mitosis
  • Models, Biological
  • Multiprotein Complexes / metabolism*
  • Protein Binding
  • Protein Domains
  • Schizosaccharomyces / growth & development
  • Schizosaccharomyces / metabolism*
  • Schizosaccharomyces pombe Proteins / chemistry
  • Schizosaccharomyces pombe Proteins / metabolism*
  • Sequence Deletion
  • Solutions
  • Spindle Pole Bodies / metabolism
  • Subcellular Fractions / metabolism
  • Tubulin / metabolism*

Substances

  • Microtubule-Associated Proteins
  • Multiprotein Complexes
  • Mzt1 protein, S pombe
  • Schizosaccharomyces pombe Proteins
  • Solutions
  • Tubulin