Here the authors show that Xist drives non-stoichiometric recruitment of SHARP/SPEN to the inactive X chromosome, including at regions not occupied by Xist, through concentration-dependent homotypic assemblies of SHARP, which is required for chromosome-wide silencing. This spatial amplification allows Xist to balance chromosome-wide silencing and specificity to the X thereby enabling Xist to silence the X, the whole X, and nothing but the X.
- Joanna W. Jachowicz
- Mackenzie Strehle
- Mitchell Guttman
