 One showed that Xist and PRC2 are spatially separated, while another showed that Xist and PRC2 are tightly linked.It is possible that several mechanisms recruit PRC2 in parallel, including direct Xist-mediated recruitment, adaptor proteins, chromatin changes, RNA pol II exclusion, or PRC1 recruitment.For instance, PRC2 recruitment is linked to PRC1-mediated H2A119 ubiquitination in differentiating embryonic stem cells (ESCs).