Genomic validation of newly identified ORIs. Visualization of HeLa Repli-seq in the UCSC Genome Browser showing three genomic regions: two (A and B) from chromosome 8 (adjacent regions; same y-axis value ranges) and one (C) from chromosome 6, spanning a total of 18.2 Mb. ORC1 peaks (black vertical lines), S1–S6 sequence-tag densities, the algorithmically identified inverted-V apexes (red filled boxes), the s50 profile (see Methods), and RefSeq genes are shown. (A) One representative inverted-V is shown as two green arrows (the right one also corresponds to a temporal transition region). (Open red circles) ORC1 peaks mapping outside inverted-V apexes. (Scale bars) 5 Mb. (D) Q-ChIP of ORC1 binding to the PRKDC ORI, the newly identified ORC1 peaks mapping to TSS of known genes (A–G) and two control regions (C1 and C2, as in Fig. 2A), using anti-ORC1 or anti-Flag (Mock) antibodies and chromatin of low-density fractions from human activated CD4⁺ T cells (see text). (Error bars) SD; n = 2. The Q-PCR probes are as in Figure 2A.