Changes over time in histone acetylation at the TSS of genes showing specific transcriptional responses to VPA. ChIP-seq was carried out on lymphoblastoid cells treated for 0, 30, 60 and 120 min with 1 mM VPA using antibodies to one of three different acetylated histones, as indicated. Changes over time are shown for each of the four categories of persistently responding genes (Fig. 2), as indicated. Box plots, configured as in Fig. 4, show the distribution of normalised read counts at the TSS of genes that showed significantly altered transcript levels at each time point. TSS probes were −500 to +500 bp around each TSS and were quantified by read count quantitation, normalised to the largest datastore.