Fig. 9.

The role played by the SF1 and SF2 insulators in TAD formation and transcription in ANT-C. (A) The boundaries of the TAD including the ftz gene are determined by the SF1 and SF2 insulators. Interacting insulators form a loop that brings the T1 enhancer closer to the Scr gene promoter. The T1 enhancer activates Scr transcription. (B) Deletion of the SF1 insulator (designated by brackets) leads to disruption of TAD but not misexpression of the ftz gene. However, the T1 enhancer does not activate Scr transcription, because a loop between insulators does not form. All designations are the same as those in Fig. 2