BEST signature at IMR90 CCCTC-factor binding regions. (a,b) Signal for BEST (accumulation of GRO-seq sense reads accompanied by anti-sense reads immediately upstream) is shown at non-promoter-associated IMR90 CTCF binding regions stratified by open chromatin loci (DHSs) (a) and H3K27ac peaks (b). Relative sense/plus read density (y-axis) is the sense/plus read density at a particular proportional position divided by the average sense/plus read density in the entire CTCF + flanking region. Proportional positions between 0 and 1 on the x-axis correspond to CTCF binding regions . Positions < 0 and > 1 correspond to flanking regions. IMR90 CTCF binding regions potentially associated with promoters or gene ends were discarded from the analysis. Non-CTCF control regions (black) were randomly generated and follow the same size distribution as IMR90 CTCF binding regions.