Identification of proteins within the nuclear factor-κB transcriptional complex including estrogen receptor-α

OBJECTIVE: The objective of the study was to determine whether cross-talk occurs between estrogen receptors (ERs) and nuclear factor-kappaB (NF-kappa B), to assess the functional consequences of such an ER/NF-kappa B interaction, and to identify other unknown regulatory proteins that may participate in the NF-kappa B transcriptional complex. STUDY DESIGN: Electromobility gel shifts, reporter gene assays, and mass spectrometry were used to identify proteins interacting with the NF-kappa B deoxyribonucleic acid (DNA) response element. RESULTS: ER and the p65 subunit of NF-kappa B colocalized on DNA. This interaction was inhibitory for ER transcriptional activity. Sequencing of proteins bound to the NF-kappa B/DNA complex identified DNA-modifying enzymes, scaffolding proteins, chaperones, and elements of the nuclear matrix. CONCLUSION: These studies have identified an inhibitory interaction between estrogen receptors and the p65 subunit of NF-kappa B with implications for estrogen action in pregnancy and cancer. New accessory proteins have also been identified that bind to protein complexes on the NF-kappa B DNA response element.