 Some studies showed that PRC2 components are not associated with Xist RNA or do not interact functionally.However another study has shown by means of mass spectrometry analysis, that two subunits of PRC2 may interact with Xist, although these proteins are also found in other complexes and are not unique components of the PRC2 complex.Biochemical studies have also shown that "in vitro" PRC2 binds the A-repeat (RepA) of Xist RNA directly and with very high affinity (dissociation constants of 10-100 nanomolar), supporting Xist-mediated recruitment of PRC2 to the X chromosome.