Updated project metadata. The Estrogen Receptor beta (ERβ), is a member of the nuclear receptor superfamily of trancriptional regulators, with oncosuppressive activities, antagonizing hormone-induced carcinogenesis and inhibiting growth and oncogenic functions in breast cancers (BCs). It is able to exert specific biological functions also in the absence of estrogen stimuli. Interaction proteomics coupled to mass spectrometry (MS) was applied to deeply characterize the nuclear interactors cooperating with unliganded ERβ and the role of RNA in mediating these iteractions.