title: Identification of a novel circadian clock modulator controlling BMAL1 expression through a ROR/REV-ERB-response element-dependent mechanism.
abstract: Circadian rhythms, biological oscillations with a period of about 24 h, are maintained by an innate genetically determined time-keeping system called the molecular circadian clockwork. Despite the physiological and clinical importance of the circadian clock, development of small molecule modulators targeting the core clock machinery has only recently been initiated. BMAL1, a core clock gene, is controlled by a ROR/REV-ERB-response element (RORE)-dependent mechanism, which plays an important role in stabilizing the period of the molecular circadian clock. Therefore, we aimed to identify a novel small molecule modulator that regulates Bmal1 gene expression in RORE-dependency, thereby influencing the molecular feedback loop of the circadian clock. For this purpose, we carried out a cell-based screen of more than 1000 drug-like compounds, using a luciferase reporter driven by the proximal region of the mouse Bmal1 promoter. One compound, designated KK-S6, repressed the RORE-dependent transcriptional activity of the mBmal1 promoter and reduced endogenous BMAL1 protein expression. More importantly, KK-S6 significantly altered the amplitude of circadian oscillations of Bmal1 and Per2 promoter activities in a dose-dependent manner, but barely affected the period length. KK-S6 effectively decreased mRNA expression of metabolic genes acting downstream of REV-ERBα, Pai-1 and Citrate synthase, that contain RORE cis-element in their promoter. KK-S6 likely acts in a RORE-dependent manner by reinforcing the REV-ERBα activity, though not by the same mechanism as known REV-ERB agonists. In conclusion, the present study demonstrates that KK-S6 functions as a novel modulator of the amplitude of molecular circadian rhythms by influencing RORE-mediated BMAL1 expression.
authors.affiliation: Department of Biological Sciences, College of Natural Sciences, Seoul National University, Seoul, South Korea; Department of Brain & Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, South Korea.
authors.forename: Jiyeon
authors.initials: J
authors.lastname: Lee
authors.affiliation: College of Pharmacy, Seoul National University, Seoul, South Korea.
authors.forename: Seungbeom
authors.initials: S
authors.lastname: Lee
authors.affiliation: Department of Biological Sciences, College of Natural Sciences, Seoul National University, Seoul, South Korea; Department of Biomedical Sciences, College of Medicine, Korea University, Seoul, South Korea.
authors.forename: Sooyoung
authors.initials: S
authors.lastname: Chung
authors.affiliation: Department of Biological Sciences, College of Natural Sciences, Seoul National University, Seoul, South Korea.
authors.forename: Noheon
authors.initials: N
authors.lastname: Park
authors.affiliation: Department of Biomedical Sciences, College of Medicine, Korea University, Seoul, South Korea.
authors.forename: Gi Hoon
authors.initials: GH
authors.lastname: Son
authors.affiliation: College of Pharmacy, Seoul National University, Seoul, South Korea.
authors.forename: Hongchan
authors.initials: H
authors.lastname: An
authors.affiliation: College of Pharmacy, Seoul National University, Seoul, South Korea.
authors.forename: Jaebong
authors.initials: J
authors.lastname: Jang
authors.affiliation: College of Pharmacy, Sunchon National University, Suncheon, South Korea.
authors.forename: Dong-Jo
authors.initials: DJ
authors.lastname: Chang
authors.affiliation: College of Pharmacy, Seoul National University, Seoul, South Korea. Electronic address: ygsuh@snu.ac.kr.
authors.forename: Young-Ger
authors.initials: YG
authors.lastname: Suh
authors.affiliation: Department of Biological Sciences, College of Natural Sciences, Seoul National University, Seoul, South Korea; Department of Brain & Cognitive Sciences, College of Natural Sciences, Seoul National University, Seoul, South Korea; Department of Brain & Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, South Korea. Electronic address: kyungjin@dgist.ac.kr.
authors.forename: Kyungjin
authors.initials: K
authors.lastname: Kim
mesh_terms: D056930:ARNTL Transcription Factors / Q000235:genetics*; D000818:Animals; D057906:Circadian Clocks / Q000235:genetics*; D025461:Feedback, Physiological / Q000502:physiology; D005786:Gene Expression Regulation / Q000235:genetics; D051379:Mice; D056953:Nuclear Receptor Subfamily 1, Group D, Member 1 / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics; D020218:Response Elements / Q000235:genetics*
chemical_list: D056930:ARNTL Transcription Factors; C538961:Bmal1 protein, mouse; C498262:Nr1d1 protein, mouse; D056953:Nuclear Receptor Subfamily 1, Group D, Member 1
keywords: Brain-muscle-ARNT-like protein 1; Circadian clock; Circadian rhythm; ROR/REV-ERB-response element; Rev-erbα; Small molecule