Fig. 2

Xist RNA tethers epigenetic regulators and contributes 3D conformation of the X chromosome. Xist RNA recruits repressive complexes such as polycomb complexes PRC1 and PRC2 to the inactive X chromosome (Xi) to facilitate heterochromatin formation, thus leading to gene silencing. On the other hand, Xist binds to BRG1 and cohesin and repels them from the Xi to prevent TAD (topologically associated domain) formation. Xist mediates the Xi folding in 3D space by tethering SMCHD1, which facilitates the merge of chromatin compartments. A/B compartments are first fused into “S1” and “S2” compartments, after SMCHD1 recruitment, further merging to compact Xi structure