Figure 2.

Nucleotide distributions at the 3′ ends of heterogeneous sequences and trimmed host leaders. (A) Nucleotide frequencies at the last eight positions of heterogeneous sequences before trimming residues attributed to prime-and-realign. At each position, enrichment was normalized to the overall nucleotide frequencies within 51-nt windows centered on all Gencode 17 TSSs. (B) Nucleotide frequencies after trimming residues attributed to prime-and-realign; otherwise, as in (A).