Fig. 4.

Dim Num1 patches mediate spindle pulling via MT sliding. (A) Quantification of spindle correction mechanisms for the indicated strains (22≤n≤52 events per strain). Error bars represent the standard error of proportion (s.e.p.). (B) Time-lapse sequence showing spindle correction via MT sliding in an Mdm36^OX kar9Δ cell expressing Num1–GFP and mRuby2–Tub1. Red arrowhead marks initiation of MT sliding at a dim cortical Num1 cluster. Yellow arrows mark the position of the astral MT plus end. Red dashed line indicates the cell outline. (C) Copy number of Num1–GFP for individual foci found along the mother cell cortex versus those found at the bud cortex mediating spindle pulling during a spindle correction assay in Mdm36^OX kar9Δ cells (n=201 and 26, respectively). Median±95% confidence interval is indicated. Diagram shows bud and mother Num1–GFP patches that were quantified in this assay. (D) Deconvolved two-color image sequence showing spindle correction via MT sliding in a NUM1–GFP VENUS–TUB1 kar9Δ cell overexpressing mRuby2-tagged Mdm36. Arrowheads mark the position of the astral MT plus end. (E) Mean preanaphase spindle velocity toward the bud or mother cell observed during a 7-min movie. Error bars represent s.e.m. n.s., not statistically significant by unpaired t-test. (F) Mean fluorescence intensity of Num1–GFP patches seen mediating spindle pulling or mitochondrial tethering in Mdm36^OX cells. Patches mediating spindle pulling were observed in the kar9Δ background. Error bars represent s.d. (G) Deconvolved two-color image sequence showing a spindle pulling event in an Mdm36^OX kar9Δ cell expressing Num1–GFP, Venus–Tub1 and Cox4–mCherry. Yellow arrowheads indicate spindle pulling by MT sliding (frames 40 s to 80 s) in a cortical region lacking mitochondria. Red arrowhead marks Num1 foci involved in mitochondrial tethering. Red dashed line indicates cell outline and the white dashed line indicates position of the bud neck.