Model validation. (a) Effect of small interfering (si)RNAp53 on irradiation (5 Gy) induced change in transcript levels at 4 hours of the 74 class 1 genes. (b) Effect of altering Sj Z score threshold for class 1 on proportion of true targets identified (% of p53 upregulated genes at 4 hours predicted; black line) and accuracy of class 1 predictions (percentage of predictions made that were verified by siRNAp53; red line). Accuracy and proportion of the data explained reveal an inverse relationship. (c) Individual comparison of the effect of siRNAp53 on 74 class 1 genes with the best M and p53 sensitivity Sj score, ranked by sensitivity. Bars represent the validation score, a Z score measuring the effectiveness of siRNAp53 on reducing post-irradiation upregulation of transcript. Higher scores indicate effective blocking of the response.