Insights into the NF-κB-DNA Interaction through NMR Spectroscopy.

Transcription factors bind specifically to their target elements in the genome, eliciting specific gene expression programs. The nuclear factor-κB (NF-κB) system is a family of proteins comprising inducible transcription activators, which play a critical role in inflammation and cancer. The NF-κB members function as dimers with each monomeric unit binding the κB-DNA. Despite the available structures of the various NF-κB dimers in complex with the DNA, the structural features of these dimers in the nucleic acid-free form are not well-characterized. Using solution NMR spectroscopy, we characterize the structural features of 73.1 kDa p50 subunit of the NF-κB homodimer in the DNA-free form and compare it with the κB DNA-bound form of the protein. The study further reveals that in the nucleic acid-free form, the two constituent domains of p50, the N-terminal and the dimerization domains, are structurally independent of each other. However, in a complex with the κB DNA, both the domains of p50 act as a single unit. The study also provides insights into the mechanism of κB DNA recognition by the p50 subunit of NF-κB.