title: Effect of Resveratrol, a SIRT1 Activator, on the Interactions of the CLOCK/BMAL1 Complex.
abstract: BACKGROUND
  In mammals, the CLOCK/BMAL1 heterodimer is a key transcription factor complex that drives the cyclic expression of clock-controlled genes involved in various physiological functions and behavioral consequences. Recently, a growing number of studies have reported a molecular link between the circadian clock and metabolism. In the present study, we explored the regulatory effects of SIRTUIN1 (SIRT1), an NAD(+)-dependent deacetylase, on CLOCK/BMAL1-mediated clock gene expression.
  
  
  METHODS
  To investigate the interaction between SIRT1 and CLOCK/BMAL1, we conducted bimolecular fluorescence complementation (BiFC) analyses supplemented with immunocytochemistry assays. BiFC experiments employing deletion-specific mutants of BMAL1 were used to elucidate the specific domains that are necessary for the SIRT1-BMAL1 interaction. Additionally, luciferase reporter assays were used to delineate the effects of SIRT1 on circadian gene expression.
  
  
  RESULTS
  BiFC analysis revealed that SIRT1 interacted with both CLOCK and BMAL1 in most cell nuclei. As revealed by BiFC assays using various BMAL1 deletion mutants, the PAS-B domain of BMAL1 was essential for interaction with SIRT1. Activation of SIRT1 with resveratrol did not exert any significant change on the interaction with the CLOCK/BMAL1 complex. However, promoter analysis using Per1-Luc and Ebox-Luc reporters showed that SIRT1 significantly downregulated both promoter activities. This inhibitory effect was intensified by treatment with resveratrol, indicating a role for SIRT1 and its activator in CLOCK/BMAL1-mediated transcription of clock genes.
  
  
  CONCLUSIONS
  These results suggest that SIRT1 may form a regulatory complex with CLOCK/BMAL1 that represses clock gene expression, probably via deacetylase activity.
authors.affiliation: Department of Biological Sciences and Brain Research Center for 21st Frontier Program in Neuroscience, Seoul National University College of Natural Sciences, Seoul, Korea.
authors.forename: Insung
authors.initials: I
authors.lastname: Park
authors.affiliation: Department of Biological Sciences and Brain Research Center for 21st Frontier Program in Neuroscience, Seoul National University College of Natural Sciences, Seoul, Korea.
authors.forename: Yool
authors.initials: Y
authors.lastname: Lee
authors.affiliation: Department of Biological Sciences and Brain Research Center for 21st Frontier Program in Neuroscience, Seoul National University College of Natural Sciences, Seoul, Korea. ; Department of Brain and Cognitive Sciences, Seoul National University College of Natural Sciences, Seoul, Korea.
authors.forename: Hee-Dae
authors.initials: HD
authors.lastname: Kim
authors.affiliation: Department of Biological Sciences and Brain Research Center for 21st Frontier Program in Neuroscience, Seoul National University College of Natural Sciences, Seoul, Korea. ; Department of Brain and Cognitive Sciences, Seoul National University College of Natural Sciences, Seoul, Korea.
authors.forename: Kyungjin
authors.initials: K
authors.lastname: Kim
keywords: BiFC analysis; CLOCK/BMAL1 heterodimer; Circadian clocks; Resveratrol; SIRT1