Identification of proteins within the nuclear factor-kappa B transcriptional complex including estrogen receptor-alpha.

Objective: The objective of the study was to determine whether cross-talk occurs between estrogen receptors (ERs) and nuclear factor-kappa-B (NF-kappaB), to assess the functional consequences of such an ER/NF-kappaB interaction, and to identify other unknown regulatory proteins that may participate in the NF-kappaB transcriptional complex.

Study Design: Electromobility gel shifts, reporter gene assays, and mass spectrometry were used to identify proteins interacting with the NF-kappaB deoxyribonucleic acid (DNA) response element.

Results: ER and the p65 subunit of NF-kappaB colocalized on DNA. This interaction was inhibitory for ER transcriptional activity. Sequencing of proteins bound to the NF-kappaB/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-kappaB with implications for estrogen action in pregnancy and cancer. New accessory proteins have also been identified that bind to protein complexes on the NF-kappaB DNA response element.