Distinct roles of the polarity factors Boi1 and Boi2 in the control of exocytosis and abscission in budding yeast

Mol Biol Cell. 2017 Nov 1;28(22):3082-3094. doi: 10.1091/mbc.E17-06-0404. Epub 2017 Sep 13.

Abstract

Boi1 and Boi2 (Boi1/2) are budding yeast plasma membrane proteins that function in polarized growth, and in cytokinesis inhibition in response to chromosome bridges via the NoCut abscission checkpoint. How Boi1/2 act in these two distinct processes is not understood. We demonstrate that Boi1/2 are required for a late step in the fusion of secretory vesicles with the plasma membrane of the growing bud. Cells lacking Boi1/2 accumulate secretory vesicles and are defective in bud growth. In contrast, Boi2 is specifically required for abscission inhibition in cells with chromatin bridges. The SH3 domain of Boi2, which is dispensable for bud growth and targets Boi2 to the site of abscission, is necessary and sufficient for abscission inhibition. Gain of function of the exocyst, a conserved protein complex involved in tethering of exocytic vesicles to the plasma membrane, rescued secretion and bud growth defects in boi mutant cells, and abrogated NoCut checkpoint function. Thus Boi2 functions redundantly with Boi1 to promote the fusion of secretory vesicles with the plasma membrane at sites of polarized growth, and acts as an abscission inhibitor during cytokinesis in response to chromatin bridges.

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics
  • Adaptor Proteins, Signal Transducing / metabolism*
  • Cell Division / physiology
  • Cell Membrane
  • Cytokinesis / physiology
  • Exocytosis / genetics
  • Exocytosis / physiology*
  • Protein Binding
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Saccharomycetales / metabolism
  • Secretory Vesicles / metabolism
  • Signal Transduction
  • rho GTP-Binding Proteins / metabolism
  • src Homology Domains / genetics

Substances

  • Adaptor Proteins, Signal Transducing
  • BOI1 protein, S cerevisiae
  • BOI2 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • rho GTP-Binding Proteins