Fig. 6.

Proposed models for the physiological role of T-bet DNA looping activity based on the in vivo 3C data. (A) T-bet functions to stabilize and maintain existing DNA loops. No new long-range DNA interactions are created. (B) T-bet creates new long-range DNA interactions, but these new interactions were not detected uniquely as T-bet–dependent interactions because of the existence of prior T-bet–independent interactions between the same 3C fragments. (C) Schematic of T-bet molecules binding simultaneously to promoter sites on genes located on different chromosomes, activating one while repressing the other.