Figure iv. Cell-cycle regulated transcripts induced by MMS and ionizing radiation. Hierarchical clustering of the cell cycle regulated genes revealed two clusters of genes, induced specifically in cells responding to MMS treatment (A) or ionizing radiation (IR) (B). Genes in these clusters are involved in a variety of cellular processes and are normally expressed at different cell-cycle phases in cycling cells. With the exception of genes involved in sulfur metabolism, the induction of these transcripts was unaffected by MEC1 deletion, suggesting that their expression changes are not directly related to the cell cycle arrest points induced by MMS or ionizing radiation.