FIGURE 9.

Schematic summary to test for dependence of IP-1 toxicity on cell cycle arrest. The image shows every aspect of the experimental system that was tested in our work. Our experimental results (R) show that IP-1 induces cell death only when cells are arrested in their cell cycle. To test this, the pheromone pathway was affected at different steps (e.g., S1, S2, etc.). For instance, IP-1 (red structure) was altered in its ability to bind Ste2p (green structure) and reduce the pheromone-like activity of IP-1 (indicated by S1). Also, different molecules were used to induce cell cycle arrest in G₀/G₁ or M phases: IP-1, α-pheromone, NaCl, NM-PPI, or nocodazole. Gene null mutants in the MAPK pathway (e.g., STE50, STE7) and other cellular programs induced by the pheromone (autophagy, filamentous growth) were tested for their participation in IP-1-induced cell death. The image indicates the inside and outside of the cell as well as the cell membrane. Broken arrow lines represent putative relationships of FIG1 that may be relevant in IP-1-induced cell death.