Fig. 2

Heavy methyl labeling of epithelial to mesenchymal transition (EMT) cell lines. a Microscopy image of epithelial cell culture at days 0, 1 and 2. Day 0 is prior stimulation with TGFβ, inducing mesenchymal transition. b On the left, workflow displaying the treatment of epithelial cells to induce EMT. Briefly, epithelial cells were plated into a new media containing heavy labeled methionine. Newly synthesized PTMs are characterized by a mass shift of 4 Da, due to the replacement of CH₃ with ¹³CD₃. On the right, examples of the possible labeling combinations for trimethylation; the number of heavy labeled methyl groups is illustrated by the number after the colon (in red). c Relative abundance of single histone PTMs in EMT in not confluent culture (top) and confluent culture (bottom). Data are the average of three biological replicates (two for day 0). Heavy labeled methylations are highlighted by different degrees of dashed bars; one heavy methyl is indicated with diagonal lines, two heavy methyl groups with a cheeseboard-like theme and three heavy methyl groups with more dense tiny squares. The relative abundance of single PTMs was obtained by summing the relative abundance of all combinatorial forms containing each given PTM