Gene-expression profiling links sulfur assimilation, methionine and glutathione pathways. Selected genes in these pathways are represented as red for induced (2 h, 100 μM AsIII and 0.5 h, 1 mM AsIII, respectively) and green for repressed. Genes in white boxes are not differentially expressed. The pathways in the blue ovals are upstream of methionine, cysteine and glutathione, and are sensitive to arsenic. The downstream pathways employ numerous redundant enzymes that are differentially expressed, but are not sensitive. LT, late time-point, 4 h, 100 μM AsIII experiment; h, human; y, yeast.