Figure 1: Spo12 promotes mitotic exit of cells with misaligned spindles.
From: Temporal and compartment-specific signals coordinate mitotic exit with spindle position
(a) Cartoon depicting mitotic exit control in budding yeast. Arrowed and capped lines indicate activating and inhibitory steps, respectively. Spindle poles are depicted as red stars and microtubules as red lines. Chromosomes are shown in black and grey rectangles. Sister chromatids are outlined with light grey lines. (b) SPO12 overexpression rescues KIN4 overexpression lethality. Serial dilutions of Gal1-KIN4 strains bearing high-copy (2 μm) or low-copy (centromeric (CEN)) plasmids carrying SPO12. Cells were spotted on Gal1-KIN4 overexpressing (SC-LEU Raf/Gal) or suppressing (SC-LEU Glu) agar plates. Gal1-KIN4 strain with BFA1 deletion serves as a control for the rescue of KIN4 overexpression lethality. (c) Examples of SPOC-deficient (1–5), misaligned nuclei/spindle (6) and correctly aligned nuclei/spindle (7) phenotypes. SPOC-deficient phenotypes arise from mitotic exit of cells with misaligned spindles. These include more than two nuclei in one cell body (1), multi-budded cells with clustered nuclei (2), broken spindle in one cell body (3, 4) and multi-polar spindle (5). Microtubules were monitored in cells carrying GFP-TUB1 as a spindle marker. Nuclei were monitored by DAPI staining. Scale bars: 3 μm. (d) SPOC integrity of kar9Δ GFP-TUB1 cells with or without additional copies of SPO12 on a low-copy (CEN) or high-copy (2 μm) plasmid. To assay SPOC integrity, percentage of SPOC-deficient phenotypes per cell population were scored. Graph is an average of three independent experiments. Error bars show s.d. Per experiment, 100 cells were counted per strain. Asterisk indicates significant difference according to two-tailed Student’s t-test (P<0.05).
