Genome-wide maps of NFKB1/p50 binding dynamics

We report the application of ChIP-Seq for high-throughput profiling of NFKB1/p50 binding dynamics. The binding profiles were performed under three conditions/models. We first examine the p50 binding in HEK293T cells during G1 and S phase. HEK293T cells were synchronized with double thymidine block method. Before and after release to S phase, ChIP was performed, and chromatin immunoprecipitated DNA was converted to libraries for sequencing with HiSeq 4000. We find that these NFKB1/p50 binding peaks in G1 phase dramatically reduced at S phase. Then, we further examine the p50 binding in HEK293T/TopBP1 cells in response to tamoxifen treatment. These cells have stable expression of TopBP1 activation domain fusion with estrogen receptor. After treatment, chromatin immunoprecipitated DNA was converted to libraries for sequencing with HiSeq 4000. We find that these NFKB1/p50 binding peaks in vehicle control sample dramatically reduced after tamoxifen treatment. Final, we compare the genome wide binding behavior of wild type p50 and mutant p50 2KR (K354R and K356R). HEK293T cells was transfected with plasmids expression HA-tagged wild type or mutation p50. Chromatin immunoprecipitated DNA was converted to libraries for sequencing with HiSeq 4000. We find that both wild type and p50 2KR mutant share similar binding profile. However, in general, p50 mutant has less binding affinity to NFKB binding sites. This study provides a preliminary but solid basis to our understanding of NFKB1/p50 binding dynamics. Overall design: ChIp-Seq experiments were performed with specific antibodies under designed condtions, and library from HEK293T input was used for background correction.