Exploration of the Role of the IκB Pest Sequence in Stripping NFκB from DNA

Nuclear factor kappa B (NFκB) transcription factors are responsible for the regulation of more than 150 target genes, their expression is induced by many classes of stimuli, and NFκBs play essential roles in the healthy regulation of cellular development and proliferation in inflammatory and immune responses. Diseases such as cancer, heart disease, Alzheimer's disease, and AIDS can be attributed to the wayward regulation of NFκB. The transcriptional activity of NFκB is commanded by its inhibitor—IκB. Two major isoforms of the inhibitor—IκBα and IκBβ—are structurally similar (i.e., crystal structures of the two exhibit a six ankyrin repeat domain followed by a largely unstructured, C-terminal PEST sequence), yet their inhibitory activities markedly differ. It has been shown that IκBα can actively “strip” NFκB from DNA in vitro, but IκBβ cannot. We are investivating a panel of “PEST swap” mutants to probe the role of the PEST sequence in the regulation of NFκB. In addition, the role of individual residues within the IκBα PEST sequence in the “stripping” phenomenon is being analyzed.