title: Critical role of RelB serine 368 for dimerization and p100 stabilization.
abstract: In mature B cells RelB-containing complexes are constitutively present in the nucleus, and they are less susceptible to inhibitory kappaB proteins. In most other cell types inhibitory kappaB proteins prevent nuclear translocation and activation of NFkappaB. We reasoned that this characteristic might be because of post-translational modifications of RelB. In Drosophila, signal-dependent phosphorylation of the Rel homologue Dorsal at serine 317 has been shown to be critical for nuclear import. The evolutionary conservation of this serine prompted us to analyze the function of the corresponding site in RelB. As a model system we used the murine S107 plasmacytoma cell line, which lacks endogenous RelB expression. Analysis of S107 cells expressing wild type RelB and serine 368 mutants reveals that serine 368 is not required for nuclear import but that it is critical for RelB dimerization with other members of the NFkappaB family. Similar effects were obtained when the conserved serine in RelA was mutated. We further demonstrate that expression of functional RelB, but not of serine 368 mutants, severely reduces p52 generation and strongly increases expression of the p52 precursor, p100. Wild type RelB, but not mutant RelB, prolonged p100 half-life. We therefore suggest an inhibitory effect of RelB on p100 processing, which is possibly regulated in a signal-dependent manner.
authors.affiliation: Department of Physiological Chemistry, Ulm University, Ulm 89081, Germany.
authors.forename: Harald Jakob
authors.initials: HJ
authors.lastname: Maier
authors.forename: Ralf
authors.initials: R
authors.lastname: Marienfeld
authors.forename: Thomas
authors.initials: T
authors.lastname: Wirth
authors.forename: Bernd
authors.initials: B
authors.lastname: Baumann
mesh_terms: D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D017124:Conserved Sequence; D019281:Dimerization; D005822:Genetic Vectors; D006801:Humans; D019169:Jurkat Cells; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D016328:NF-kappa B / Q000737:chemistry*; D052003:NF-kappa B p52 Subunit; D010766:Phosphorylation; D011233:Precipitin Tests; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D011518:Proto-Oncogene Proteins / Q000737:chemistry* / Q000502:physiology; D012694:Serine / Q000737:chemistry*; D015398:Signal Transduction; D013997:Time Factors; D051841:Transcription Factor RelB; D014157:Transcription Factors / Q000737:chemistry* / Q000502:physiology; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D016328:NF-kappa B; D052003:NF-kappa B p52 Subunit; D011518:Proto-Oncogene Proteins; C497593:RELB protein, human; C497594:Relb protein, mouse; D014157:Transcription Factors; D051841:Transcription Factor RelB; D012694:Serine