A novel protein modulator of non-genomic activity of nuclear receptors (MNAR), which interacts with estrogen receptors alpha (ERα), estrogen receptor beta (ERβ), and other nuclear receptors, was discovered and characterized. An MNAR-ER complex, in vitro and in vivo, relates to nucleic acids, antisense, recombinant expression of nucleic acids, as well as host cells, compositions and assays that utilize the nucleic acids and protein of this invention.