Tri-C analysis from resting (0 h, bottom matrix) and activated (72 h, top matrix) primary B cells using Eu as the capture viewpoint. The matrices consist of 1-kb bins spanning the Igh locus. Displayed are the reporter fragment counts from >=3-way reads normalized by the number of NlaIII restriction sites per bin and adjusted to a total of 300,000 counts per matrix. The bins containing the Eu capture probe are blanked (black stripes). The annotation of genes, enhancers, and 3'CBE is shown with switch (S) regions of each Igh gene indicated as a red bar. The blue lines within the matrix indicate the location of bins corresponding to Eu enhancer, Ig1 promoter, Eg1 enhancer, and the four enhancers (hs sites) within the 3'RR. The histogram in between the matrices shows the cumulative contact frequency in each bin of the matrix. A mappability track in gray (Mapp.) is also provided. Note that Sg1 is poorly mappable due to its highly repetitive sequence as is the core of Su and a portion of the palindromic sequence between hs1, hs2, and hs3b. The six zones of contact enrichment are encircled and labeled (zones 1-6). Zone 1: Eu with the Ighm locale. Zone 2: Eu-Ighm-Ighg1. Zone 3: Eu-Ighm-3'RR-3'CBE. Zone 4: Eu-Ighg1. Zone 5: Eu-Ighg1-3'RR-3'CBE. Zone 6: Eu-3'RR-3'CBE. Zones 5 and 6 represent biological 3-way interactions.
