title: Krüppel-associated box-associated protein 1 negatively regulates TNF-α-induced NF-κB transcriptional activity by influencing the interactions among STAT3, p300, and NF-κB/p65.
abstract: Krüppel-associated box-associated protein 1 (KAP1) is thought to act mainly as a scaffold for protein complexes, which together silence transcription by triggering the formation of heterochromatin. Using small interfering RNA-mediated KAP1 knockdown, we found that endogenous KAP1 negatively regulated TNF-α-induced IL-6 production in HeLa cells. KAP1 is likely to modulate the binding of NF-κB to the IL-6 promoter because KAP1 knockdown enhanced TNF-α-induced NF-κB-luciferase activity, but not IκBα degradation. Of importance, we found negative regulatory effects of KAP1 on the serine phosphorylation of STAT3, the acetylation of NF-κB/p65 by p300, and the nuclear localization of NF-κB/p65. In addition, KAP1 associated with NF-κB/p65 and inhibited the binding between NF-κB/p65 and p300. Thus, KAP1 is likely to negatively control the acetylation of NF-κB/p65, which is critical for its nuclear retention. Taken together, KAP1 modulated the acetylation of NF-κB/p65 by interfering with the interactions among STAT3, p300, and NF-κB/p65, resulting in reduced IL-6 production after TNF-α stimulation. Our findings that KAP1 directly interacts with transcriptional factors are new, and will inform further research to elucidate KAP1 function.
authors.affiliation: Department of Immunology, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
authors.forename: Shinya
authors.initials: S
authors.lastname: Kamitani
authors.forename: Sumihito
authors.initials: S
authors.lastname: Togi
authors.forename: Osamu
authors.initials: O
authors.lastname: Ikeda
authors.forename: Misa
authors.initials: M
authors.lastname: Nakasuji
authors.forename: Asuka
authors.initials: A
authors.lastname: Sakauchi
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Sekine
authors.forename: Ryuta
authors.initials: R
authors.lastname: Muromoto
authors.forename: Kenji
authors.initials: K
authors.lastname: Oritani
authors.forename: Tadashi
authors.initials: T
authors.lastname: Matsuda
mesh_terms: D015153:Blotting, Western; D047369:Chromatin Immunoprecipitation; D050881:E1A-Associated p300 Protein / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D015870:Gene Expression; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D015850:Interleukin-6 / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D008856:Microscopy, Fluorescence; D016328:NF-kappa B / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D034741:RNA, Small Interfering; D012097:Repressor Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050796:STAT3 Transcription Factor / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics* / Q000276:immunology; D014158:Transcription, Genetic; D000076183:Tripartite Motif-Containing Protein 28; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000276:immunology / Q000378:metabolism*
chemical_list: D015850:Interleukin-6; D016328:NF-kappa B; D034741:RNA, Small Interfering; D012097:Repressor Proteins; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D014409:Tumor Necrosis Factor-alpha; D050881:E1A-Associated p300 Protein; C494360:EP300 protein, human; C101116:TRIM28 protein, human; D000076183:Tripartite Motif-Containing Protein 28