Fig. 3: Genomic distribution of initiation sites.

a Distribution of initiation zone widths. b High-resolution replication timing data and initiation index plotted for a representative region of chromosome 3. The profile of replication timing for HCT116 cells is from Zao et al.²⁴. c, d Average initiation index ±100 kb around annotated TSS and TTS in the human genome. Initiation index data are categorised by transcriptional activity (c) or gene length (d). For the gene length analysis only the 50% most transcriptionally active genes were included. e Heat map representation of data in panel d sorted by gene length. Broken lines indicate the position of TSS and TTS. f Equivalent heat map representation of RFD^ε|α (from Supplementary Fig. 5a) aligned at TSS and TTS. g Average RFD for the relative positions from TSS to TTS for genes scaled to the same arbitrary length. RFD^ε|α values were converted to rightward fork proportion. For this analysis, only the 50% most transcriptionally active genes were included. h Schematic representation of initiation and termination of replication forks as well as fork directionality around a representative gene.