Fig. 7
Opening of chromatin by BORIS facilitates binding of other transcriptional factors. a Scatter plot displaying the enrichment of 190 TF motifs at CTCF/BORIS binding sites that reprogrammed into active promoters, compared to transcriptionally silent CTCF/BORIS sites in NIH3T3 + BORIS (clone#2) cells. b MAZ and MXI1 motifs are significantly enriched at CTCF/BORIS binding sites converted into active promoters. c Genome browser view illustrates the recruitment of TBP, HCFC1, MXI1, and MAZ proteins at the CTCF site within the Rbpjl promoter, activated by BORIS binding in NIH3T3 + BORIS (clone#2) cells. The activated promoter is highlighted by a red open box. d Left panel: Scatter plot of normalized read counts (log10) for HCFC1 occupancy at the combined set of HCFC1 binding sites (46,287) in NIH3T3 + BORIS (clone#2) cells compared to the same genomic sites in EV cells. Right panel: Heatmap of CTCF (red), BORIS (blue), and HCFC1 (brown) occupancy at the 19,519 HCFC1 sites from the left panel (connected by red arrow). e TF motifs enriched at HCFC1 peaks (60 bp around the summit of peak) in NIH3T3 + EV versus NIH3T3 + BORIS (clone#2) cells. f Heatmap of BORIS (blue), TBP (purple), HCFC1 (brown), MXI1 (orange), and MAZ (green) occupancy at the 5871 CTCF/BORIS binding sites converted into active promoters in NIH3T3 + BORIS (clone#2) cells compared to NIH3T3 + EV cells from Fig. 4h. g Summary of epigenetic reprogramming: BORIS binding recruits SRCAP, which replaces H2A histone with H2A.Z, leading to the opening of chromatin around CTCF sites. This, in turn, attracts other TFs to bind and stimulate transcription, resulting in the conversion of transcriptionally inert CTCF sites into active promoters