PG- and EGCG-induced elevation of ROS levels is required for the decrease in the levels of histone H3K36me2 in the rRNA gene promoter and consequent rRNA transcription. (A) MCF-7 cells were treated with 50 μM GA, PG, or EGCG with or without glutathione (GSH) or N-acetyl-L-cysteine (NAC), and cultured in the presence of DCFDA, a cell-permeable ROS probe. Fluorescence was measured at the indicated time-point. The signal intensity was normalized to that of blank condition (no cells) without treatments; the mean values (n = 3) are shown. (B) MCF-7 cells were treated with or without 50 μM PG or EGCG, in the presence or absence of 0.5 mM GSH or 0.5 mM NAC, for 4 h. Total RNA was extracted, and the levels of rRNA transcripts (pre-rRNA) (left panel) and KDM2A mRNA (right panel) were determined using qRT-PCR. The results are shown as the fold change in relation to cells in the absence of compounds. (C) MCF-7 cells were treated with or without 50 μM PG or EGCG, in the presence or absence of 0.5 mM GSH or 0.5 mM NAC, for 4 h. The levels of H3K36me2, H3K36me3, and KDM2A in the rRNA gene promoter were analyzed via ChIP. The results are shown as the fold change in relation to cells in the absence of compounds. The experiments in (B,C) were performed more than three times, and the mean values with standard deviations are shown. * p < 0.05.