SMARCA4 Rescue Profiling [ChIP]

Mutations in SMARCA4, a central ATPase of the human BAF/PBAF chromatin remodeling complexes, cause developmental abnormalities and promote cancer development. The pathogenic effects of SMARCA4 loss are often linked to the de-regulation of a relatively small number of key target genes. Here, to understand how chromatin remodeling by SMARCA4 results in specific transcriptional perturbations, we used genome engineering to correct a homozygous mutation in SMARCA4 in the well-characterized lung adenocarcinoma A549 cell line and profiled changes in SMARCA2/4 occupancy, chromatin accessibility, histone marks and transcription. Restoration of SMARCA4 causes a dramatic increase in chromatin accessibility at low affinity TF binding sites. Despite the widespread increase in chromatin accessibility, we observe comparatively attenuated changes in gene expression. Although there is a marked correlation between the number of local activated DHSs and the transcriptional responsivity of a gene, the influence of distal DHSs appears modified by a gene's promoter architecture and domain-scale chromatin organization. The largest changes in expression occur for genes in isolated, SMARCA4 sensitive chromatin domains that undergo region-wide chromatin remodeling upon reintroduction of SMARCA4. Our results reveal that interactions between distal enhancers, genome organization, and promoter architecture add transcriptional specificity to the global chromatin effects of BAF/PBAF complex perturbation and target the response to key developmental pathways. Overall design: Regulatory profiling of a lung adenocarcinoma cell line with and without SMARCA4. The loss of function mutation in SMARC4A in the SMARCA4-null cell line, A549, was corrected and DNaseI-Seq, RNA-Seq, and CUT-&-RUN ChIP-Seq was performed to study the effects of the correction on the chromatin landscape.