YAN21/8d (ddc1D), YFP62/1d (ddc1Ddpb11-1) and YMIC5A3 (mec1-1) were synchronized in G1 with a-factor and released into fresh medium supplemented with 200 mM HU. 90 min later precocious ingression into mitosis was monitored measuring spindle elongation by indirect immunofluorescence. Representa- tive pictures are shown (blue = DNA; red = tubulin). Spindle length of 200 cells for each sample was measured and the frequencies of the different spindle length classes are shown in the lower panel. (TIF) Figure S4 Hydroxyurea does not elicit a DNA damage response in the drc1-1 and dpb4D mutants. (A) Strains K699 (WT), Y799 (drc1-1), YAN21/8d (ddc1D), YFP218/1a (ddc1Ddrc1-1) and YFP62/1d (ddc1Ddpb11-1) were grown to mid-log phase, synchro- nized in G1 with a-factor and released into fresh medium supplemented with 200 mM HU. After 90 min Rad9 phosphor- ylation was assayed by SDS-PAGE and western blotting. (B) Strains K699 (WT), YFP167/1a (dpb4D), YAN21/8d (ddc1D), References 1. 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