title: Identification of an N-terminal truncation of the NF-κB p65 subunit that specifically modulates ribosomal protein S3-dependent NF-κB gene expression.
abstract: NF-κB is a pleiotrophic transcription factor that plays a prominent regulatory role in various cellular processes. Although previous efforts have focused on its activation, how NF-κB selects specific target genes in response to discrete signals remains puzzling. In addition to the well defined Rel protein components of NF-κB, the ribosomal protein S3 (RPS3) was identified to be an essential component of specific NF-κB complexes. RPS3 synergistically interacts with the NF-κB p65 subunit to achieve optimal binding and transactivation of a subset of NF-κB target genes, thus providing regulatory specificity. Emerging evidence suggests an important role for the RPS3-p65 interaction in context-specific NF-κB gene transcription. The food-borne pathogen Escherichia coli O157:H7 impacts the transcription of a subset of NF-κB target genes encoding proinflammatory cytokines and chemokines in host cells by preventing the nuclear translocation of RPS3, but not p65. The N terminus of p65 is crucial for RPS3 binding. Although several p65 N-terminal fragments are generated by either protease cleavage or alternative mRNA splicing under certain pathophysiological conditions, the role of these fragments in modulating NF-κB signaling, in particular RPS3-dependent selective gene transcription, has not been fully characterized. Here we report that an N-terminal fragment of p65 (amino acids 21-186) can selectively modulate NF-κB gene transcription by competing for RPS3 binding to p65. This 21-186 fragment preferentially localizes in the cytoplasm where it delays stimuli-induced RPS3 nuclear translocation, without affecting the nuclear translocation of p65. Our findings thus uncover a new cytoplasmic function for the N-terminal domain of p65 and provide a novel strategy for selective inhibition of NF-κB gene transcription.
authors.affiliation: Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, The Johns Hopkins University, Baltimore, Maryland 21205, USA.
authors.forename: Eric M
authors.initials: EM
authors.lastname: Wier
authors.forename: Jordan
authors.initials: J
authors.lastname: Neighoff
authors.forename: Xin
authors.initials: X
authors.lastname: Sun
authors.forename: Kai
authors.initials: K
authors.lastname: Fu
authors.forename: Fengyi
authors.initials: F
authors.lastname: Wan
mesh_terms: D000818:Animals; D053148:Caspase 3 / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D006801:Humans; D019169:Jurkat Cells; D008213:Lymphocyte Activation / Q000235:genetics; D051379:Mice; D008954:Models, Biological; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D021122:Protein Subunits / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport; D012269:Ribosomal Proteins / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics; D013329:Structure-Activity Relationship; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology; D051996:Transcription Factor RelA / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D050505:Mutant Proteins; D021122:Protein Subunits; C578290:RPS3 protein, human; D012269:Ribosomal Proteins; D051996:Transcription Factor RelA; C044152:ribosomal protein S3; D053148:Caspase 3