Pre-treatment histone modification levels at the TSS of genes showing specific transcriptional responses to VPA. Box plots show the levels of the indicated histone modifications, in untreated cells, for genes showing different types of transcriptional response to 1 mM VPA (Fig. 2), namely up- or down-regulation, with or without a delay, as indicated. Modifications were detected by ChIP-seq using chromatin from lymphoblastoid cells treated with 1 mM VPA. TSS probes were −500 to +500 bp around each TSS and were quantified by read count, normalised to the largest datastore. The horizontal line within each box represents the median value, the upper and lower extremities of the box represent the 75th and 25th percentile and the whiskers show the median ± twice the interquartile range.