title: The Nuclear Protein IκBζ Forms a Transcriptionally Active Complex with Nuclear Factor-κB (NF-κB) p50 and the Lcn2 Promoter via the N- and C-terminal Ankyrin Repeat Motifs.
abstract: The nuclear protein IκBζ, comprising the N-terminal trans-activation domain and the C-terminal ankyrin repeat (ANK) domain composed of seven ANK motifs, activates transcription of a subset of nuclear factor-κB (NF-κB)-dependent innate immune genes such as Lcn2 encoding the antibacterial protein lipocalin-2. Lcn2 activation requires formation of a complex containing IκBζ and NF-κB p50, a transcription factor that harbors the DNA-binding Rel homology region but lacks a trans-activation domain, on the promoter with the canonical NF-κB-binding site (κB site) and its downstream cytosine-rich element. Here we show that IκBζ productively interacts with p50 via Asp-451 in the N terminus of ANK1, a residue that is evolutionarily conserved among IκBζ and the related nuclear IκB proteins Bcl-3 and IκBNS Threonine substitution for Asp-451 abrogates direct association with the κB-site-binding protein p50, complex formation with the Lcn2 promoter DNA, and activation of Lcn2 transcription. The basic residues Lys-717 and Lys-719 in the C-terminal region of ANK7 contribute to IκBζ binding to the Lcn2 promoter, probably via interaction with the cytosine-rich element required for Lcn2 activation; glutamate substitution for both lysines results in a loss of transcriptionally active complex formation without affecting direct contact of IκBζ with p50. Both termini of the ANK domain in Bcl-3 and IκBNS function in a manner similar to that of IκBζ to interact with promoter DNA, indicating a common mechanism in which the nuclear IκBs form a regulatory complex with NF-κB and promoter DNA via the invariant aspartate in ANK1 and the conserved basic residues in ANK7.
authors.affiliation: From the Department of Biochemistry, Kyushu University Graduate School of Medical Sciences, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Kohda
authors.affiliation: From the Department of Biochemistry, Kyushu University Graduate School of Medical Sciences, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
authors.forename: Soh
authors.initials: S
authors.lastname: Yamazaki
authors.affiliation: From the Department of Biochemistry, Kyushu University Graduate School of Medical Sciences, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan hsumi@med.kyushu-u.ac.jp.
authors.forename: Hideki
authors.initials: H
authors.lastname: Sumimoto
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D000081242:B-Cell Lymphoma 3 Protein; D057809:HEK293 Cells; D006801:Humans; D020672:I-kappa B Proteins / Q000235:genetics / Q000378:metabolism*; D000071068:Lipocalin-2 / Q000096:biosynthesis* / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D052002:NF-kappa B p50 Subunit / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000502:physiology*
chemical_list: D000081242:B-Cell Lymphoma 3 Protein; C000631344:BCL3 protein, human; C000631345:Bcl3 protein, mouse; D020672:I-kappa B Proteins; D000071068:Lipocalin-2; D052002:NF-kappa B p50 Subunit; C491366:Nfkbie protein, mouse; D011518:Proto-Oncogene Proteins; D014157:Transcription Factors; C071332:Lcn2 protein, mouse; C073701:Nfkb1 protein, mouse
keywords: Bcl-3; IκBNS; IκBζ; NF-κB transcription factor; ankyrin repeat; gene expression; lipocalin-2; protein motif; protein-DNA interaction; protein-protein interaction