title: N-terminal determinants of I kappa B alpha necessary for the cytoplasmic regulation of c-Rel.
abstract: I kappa B alpha is a dual regulator of Rel/NF-kappa B transcription factors. I kappa B alpha retains inactive NF-kappa B dimers in the cytoplasm, and inhibits their DNA-binding and transcriptional activities in the nucleus. Our previous studies identified discrete functional domains in I kappa B alpha responsible for the cytoplasmic and nuclear regulation of c-Rel. Determinants necessary for regulating c-Rel in the nucleus mapped to the central ankyrin domain of I kappa B alpha and a few negatively-charged amino acids that follow in the C-terminal PEST region. In contrast, sequences involved in the cytoplasmic regulation of c-Rel reside in the N-terminal and central ankyrin domains of I kappa B alpha. Here, we present a refined mapping of the N-terminal determinants of I kappa B alpha necessary for the cytoplasmic regulation of c-Rel homodimers. We demonstrate that amino acids 48 - 58 in p40/I kappa B alpha are essential to block the nuclear localization of c-Rel dimers. These data define a region of I kappa B alpha that may be required for optimal masking of the c-Rel NLS, or for the nuclear export of c-Rel/I kappa B alpha complexes. These findings highlight a novel function for the N-terminus of I kappa B alpha in the control of the subcellular localization of Rel/NF-kappa B dimers. Given the implication of deregulated NF-kappa B activity in hematopoietic and solid tumors, our findings predict that certain alterations in this domain of I kappa B alpha may have severe biological repercussions.
authors.affiliation: Center for Advanced Biotechnology, University of Medicine and Dentistry of New Jersey, New Jersey, NJ 08854-5638, USA.
authors.forename: I
authors.initials: I
authors.lastname: Luque
authors.forename: W X
authors.initials: WX
authors.lastname: Zong
authors.forename: C
authors.initials: C
authors.lastname: Chen
authors.forename: C
authors.initials: C
authors.lastname: Gélinas
mesh_terms: D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D003593:Cytoplasm / Q000378:metabolism / Q000502:physiology*; D004247:DNA / Q000037:antagonists & inhibitors / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D020672:I-kappa B Proteins; D016297:Mutagenesis, Site-Directed; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D020569:Proto-Oncogene Proteins c-rel / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000502:physiology; D017384:Sequence Deletion; D015534:Trans-Activators / Q000037:antagonists & inhibitors / Q000502:physiology; D014162:Transfection
chemical_list: D004268:DNA-Binding Proteins; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D010446:Peptide Fragments; D020569:Proto-Oncogene Proteins c-rel; D015534:Trans-Activators; D000072000:NF-KappaB Inhibitor alpha; D004247:DNA