Transcriptional regulation and chromatin architecture maintenance are decoupled modular functions at the Sox2 locus

How distal regulatory elements control gene transcription and chromatin topology is not clearly defined, yet these processes are closely linked in lineage specification during development. Through allele-specific genome editing and chromatin interaction analyses of the Sox2 locus in mouse embryonic stem cells, we found a striking disconnection between transcriptional control and chromatin architecture. We trace nearly all Sox2 transcriptional activation to a small number of key transcription factor binding sites, whose deletions have no effect on promoter-enhancer interaction frequencies or topological domain organization. Local chromatin architecture maintenance, including at the topologically associating domain (TAD) boundary downstream of the Sox2 enhancer, is widely distributed over multiple transcription factor-bound regions and maintained in a CTCF-independent manner. Furthermore, disruption of promoter-enhancer interactions by ectopic chromatin loop formation has no effect on Sox2 expression. These findings indicate that many transcription factors are involved in modulating chromatin architecture independently of CTCF.