Motif and information content analysis of all identified PA clusters. (a) 6-mer sequence motifs enriched in the region surrounding PA clusters. The raw data from all 13 tissues were combined for PA cluster calling. The sequence from 50 nt upstream and downstream of PA clusters was extracted for motif analysis. The information contents of nucleotide sequences surrounding known and novel PA clusters are shown in (b) and (c), respectively. The zero position is the mode of PA clusters. (d) Histogram of sequence motifs enriched in NP/BP and WP PA clusters. HOMER was first used to identify 6-mer motifs enriched in 100-bp regions surrounding NP/BP and WP clusters. The frequency of each enriched motif (p value < 1 × 10-5) is shown by evenly dividing the 100 bp into 100 bins (X-axis), with 0 denotes the mode of the cluster.