Fig. 4. Apoptosis in orc2-1 cells is stimulated by the Mec1p checkpoint protein and coincides with a Rad53-dependent DNA-damage response. (A) Production of Mec1p stimulates the production of ROS in mec1-21 orc2-1 cells. (B) Rad53p phosphorylation in GA1410 orc2-1 and W303 wild-type cells. orc2-1 (1/10 ROS) are strain YB0057. (C) Induction of HUG1 expression in GA1410 orc2-1 and wild-type cells. Signals are arbitrary units of fluorescently labeled cDNA produced from mRNA isolated from cells shifted to 37°C for indicated times and hybridized to HUG1 sequences on an Affymetrix microarray chip. Values represent the average of two independent experiments without subtraction of background.