Classification and distribution of TSS. (A) Classification scheme of transcription start sites adapted from Dötsch et al. . White arrows indicate genes. P: Protein-coding gene-dependent TSS located within a 500 bp range upstream of annotated start codons. I: Intragenic TSS situated within an annotated gene on the same strand. A: TSS localized antisense to an annotated gene. O: Orphan TSS not located in a promoter region or a gene on the same strand. (B) Distribution of transcription start sites identified in this study. Numbers in brackets give the amount of instances for each class. Numbers in the legend give the total amount of every class.