Core circadian protein CLOCK is a positive regulator of NF-κB–mediated transcription

• Published in: Proceedings of the National Academy of Sciences - PNAS 2012-09, Vol.109 (37), p.E2457-E2465
• Main Authors: Spengler, Mary L, Kuropatwinski, Karen K, Comas, Maria, Gasparian, Alexander V, Fedtsova, Natalia, Gleiberman, Anatoli S, Gitlin, Ilya I, Artemicheva, Natalia M, Deluca, Krysta A, Gudkov, Andrei V, Antoch, Marina P
• Format: Article
• Language: English
• Subjects: Analysis of Variance; animal models; Animals; Biological Sciences; Blotting, Western; circadian rhythm; Circadian Rhythm - physiology; CLOCK Proteins - metabolism; Electrophoretic Mobility Shift Assay; Enzyme-Linked Immunosorbent Assay; fibroblasts; Gene Expression Regulation - genetics; Gene Expression Regulation - immunology; Gene Expression Regulation - physiology; genes; hepatocytes; Humans; immune response; immunomodulators; Immunoprecipitation; linkage (genetics); Luciferases; Mice; Mice, Inbred BALB C; Microscopy, Fluorescence; mutation; pathogens; Peptides; PNAS Plus; transcription (genetics); transcription factor NF-kappa B; Transcription Factor RelA - metabolism; Transcription, Genetic - genetics; Transcription, Genetic - physiology; transcriptional activation
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1206274109

The circadian clock controls many physiological parameters including immune response to infectious agents, which is mediated by activation of the transcription factor NF-κB. It is widely accepted that circadian regulation is based on periodic changes in gene expression that are triggered by transcriptional activity of the CLOCK/BMAL1 complex. Through the use of a mouse model system we show that daily variations in the intensity of the NF-κB response to a variety of immunomodulators are mediated by core circadian protein CLOCK, which can up-regulate NF-κB–mediated transcription in the absence of BMAL1; moreover, BMAL1 counteracts the CLOCK-dependent increase in the activation of NF-κB–responsive genes. Consistent with its regulatory function, CLOCK is found in protein complexes with the p65 subunit of NF-κB, and its overexpression correlates with an increase in specific phosphorylated and acetylated transcriptionally active forms of p65. In addition, activation of NF-κB in response to immunostimuli in mouse embryonic fibroblasts and primary hepatocytes isolated from Clock -deficient mice is significantly reduced compared with WT cells, whereas Clock -Δ19 mutation, which reduces the transactivation capacity of CLOCK on E-box–containing circadian promoters, has no effect on the ability of CLOCK to up-regulate NF-κB–responsive promoters. These findings establish a molecular link between two essential determinants of the circadian and immune mechanisms, the transcription factors CLOCK and NF-κB, respectively.