Fig. 2

Triplex-forming sites (TFSs) are enriched in TADs, boundaries, and anchors but evenly distributed across TADs. (A) Illustration describing the procedure to perform a statistical test to check for the enrichment of TFSs in domains (or boundaries or loop anchors). The observed coverage of TFSs in all the domains (or boundaries or anchors) is the sum of all the base pairs in the domains (or boundaries or anchors) that overlap with the TFSs. Expected coverage is generated by randomly permuting the TFSs within the genome and computing the coverage of this random set with the domains (or boundaries or anchors). This random shuffling is performed 1000 times, for each shuffled set; an expected coverage is obtained to generate a distribution of expected coverage. These distributions are checked for normality using the Anderson-Darling normality test. Distribution of expected coverage (blue) versus the observed coverage (vertical red line) of TFSs in domains, boundaries, and anchors are shown in panels (B), (C), and (D), respectively for the HeLa cell line. (E) Frequencies of observed TFSs are evenly distributed across TADs and not significantly different from expected frequencies (p-value > 0.1 using Kolmogorov-Smirnov test). The graph is for the HeLa cell line