 During the establishment phase of X Chromosome Inactivation (XCI), Xist RNA, the master regulator of this process, spreads "in cis" along the future inactive X (Xi) and recruits repressive chromatin-remodelling complexes.Among these, Xist recruits proteins of the Polycomb repressive complexes.Whether Xist directly recruits Polycomb repressive complex 2 (PRC2) to the chromatin or this recruitment is the consequence of Xist-mediated changes on the chromatin has been object of intense debate.