title: Mechanisms by which IkappaB proteins control NF-kappaB activity.
abstract: The biological activity of the transcription factor NF-kappaB is differentially controlled by three IkappaB proteins, Ikappa Balpha, Ikappa Bbeta, and Ikappa Bepsilon. We have examined the molecular basis for the differential inhibitory strengths of IkappaB proteins by constructing hybrid IkappaBs and found that the first ankyrin repeat of Ikappa Balpha is responsible for its strong inhibitory effect. Swapping a putative beta-turn within the first ankyrin repeat between the strong Ikappa Balpha and the weak IkappaBbeta inhibitors switches their in vivo inhibitory activity on NF-kappaB. The qualitatively distinct contacts made by this beta-turn in Ikappa Balpha and Ikappa Bbeta with NF-kappaB determine the efficiency by which IkappaBs sequester NF-kappaB to the cytoplasm, thus explaining their distinct effects on gene activity.
authors.affiliation: Department of Biochemistry and Molecular Biophysics, Columbia University, 630 West 168th Street, New York, NY 10032, USA.
authors.forename: S
authors.initials: S
authors.lastname: Simeonidis
authors.forename: D
authors.initials: D
authors.lastname: Stauber
authors.forename: G
authors.initials: G
authors.lastname: Chen
authors.forename: W A
authors.initials: WA
authors.lastname: Hendrickson
authors.forename: D
authors.initials: D
authors.lastname: Thanos
mesh_terms: D000595:Amino Acid Sequence; D017487:Ankyrins; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D020672:I-kappa B Proteins; D008958:Models, Molecular; D008969:Molecular Sequence Data; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D011485:Protein Binding; D017433:Protein Structure, Secondary; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D020449:Repetitive Sequences, Amino Acid
chemical_list: D017487:Ankyrins; D004268:DNA-Binding Proteins; C083487:I kappa B beta protein; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; C105627:NFKBIE protein, human; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D000072000:NF-KappaB Inhibitor alpha