Acute depletion of CTCF rewires genome-wide chromatin accessibility
Accumulated data suggest that transcription factor CTCF is indispensable to define topologically associated domain (TAD) boundaries and to maintain intra-TAD chromatin loop structures. However, upon genome-wide acute depletion of CTCF, the discrepancy between global reduction of chromatin interactions and minimal alteration of transcription has been evidently observed. To understand CTCF's direct role in chromatin accessibility and global transcriptional regulation, we have systematically integrated data collected from ATAC-seq, RNA-seq, whole genome bisulfite-seq, Cut&Run and HiC in a previously established CTCF-miniAID knock-in cell lines. Acute degradation of CTCF markedly rewires genome-wide chromatin accessibility but not DNA methylation. Differentially altered ATAC-seq peaks are highly associated with adjacent CTCF binding sites, supporting the direct link between CTCF occupancy and its surrounding chromatin accessibility. Increased ATAC-seq peaks upon CTCF loss are notably associated with enhanced transcription at promoter regions and insulator sites, while decreased ATAC-seq peaks are significantly enriched at DNA loops. Furthermore, using CTCF associated multi-Omics data we have established a combinatorial data analysis pipeline to discover novel CTCF mediated insulators in the genome, by which we have successfully identified 67 novel insulators at non-coding regions distal to promoters. Functional CRISPR interference (CRISPRi) unconstrained the repressive transcriptional regulation of target genes. In sum, using CTCF acute depletion cell model and multi-Omics analysis, we concluded that CTCF loss rewires genome-wide chromatin accessibility, which plays a critical role for transcriptional regulation. Overall design: Examination of chromatin accessibility by ATAC-seq and DNA methylation by WGBS in human SEM cell line in control and CTCF knockout by AID.