ESTROGEN RECEPTOR-DEPENDENT FORMATION OF 2 DISTINCT MULTIPROTEIN COMPLEXES ON THE HUMAN PS2 GENE REGULATORY SEGMENT - PARTICIPATION OF A C-FOS RELATED PROTEIN

DNA-protein interactions around the regulatory region of the pS2 gene were studied to gain insight into the mechanisms that operate in the e strogen receptor regulated expression of this gene in the MCF-7 human breast cancer cell. Using a revised photocrosslinking technology in co mbination with gel retardation assays, two distinct multiprotein DNA c omplexes were shown to assemble in an estrogen receptor-dependent proc ess. Immunological analysis demonstrated the participation of both the estrogen receptor and a c-fos related protein in the formation of the se complexes. The results support a model of estrogen receptor functio n in which the receptor facilitates the formation of multiprotein comp lexes at DNA sites that can regulate the transcription of a hormone re sponsive gene by RNA polymerase II and any additional general transcri ption machinery. These receptor-containing complexes are referred to a s ''receptorsomes.''