title: Circadian Dbp transcription relies on highly dynamic BMAL1-CLOCK interaction with E boxes and requires the proteasome.
abstract: The transcription factors BMAL1 and CLOCK drive the circadian transcription of clock and clock-controlled genes, such as Dbp. To investigate the kinetics of BMAL1 binding to target genes in real time, we generated a cell line harboring tandem arrays of Dbp repeats and monitored the binding of a fluorescent BMAL1 fusion protein to these arrays by time-lapse microscopy. BMAL1 occupancy at the Dbp locus was highly circadian and strictly dependent on CLOCK. Moreover, BMAL1-CLOCK associations with Dbp were extremely unstable and displayed stochastic, proteasome-dependent fluctuations. Proteasome inhibition prolonged the residence time of BMAL1-CLOCK but resulted in an immediate attenuation of Dbp transcription. In cells harboring a single Dbp-luciferase reporter gene copy, this silencing was shown to be caused by a decrease in both the frequencies and sizes of transcriptional bursts. Thus, BMAL1 and CLOCK may act as Kamikaze activators, in that they are rapidly degraded once bound to Dbp chromatin.
authors.affiliation: Department of Molecular Biology, Sciences III, University of Geneva, and National Centre of Competence in Research Frontiers in Genetics, 1211 Geneva, Switzerland.
authors.forename: Markus
authors.initials: M
authors.lastname: Stratmann
authors.forename: David Michael
authors.initials: DM
authors.lastname: Suter
authors.forename: Nacho
authors.initials: N
authors.lastname: Molina
authors.forename: Felix
authors.initials: F
authors.lastname: Naef
authors.forename: Ueli
authors.initials: U
authors.lastname: Schibler
mesh_terms: D056930:ARNTL Transcription Factors / Q000235:genetics / Q000378:metabolism; D000107:Acetylation; D000818:Animals; D056926:CLOCK Proteins / Q000235:genetics / Q000378:metabolism; D002843:Chromatin / Q000235:genetics / Q000378:metabolism; D057906:Circadian Clocks / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D006657:Histones / Q000378:metabolism; D051379:Mice; D041681:NIH 3T3 Cells; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D011485:Protein Binding; D059010:Single-Cell Analysis; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D056930:ARNTL Transcription Factors; C538961:Bmal1 protein, mouse; D002843:Chromatin; D004268:DNA-Binding Proteins; C498260:Dbp protein, mouse; D006657:Histones; D014157:Transcription Factors; D056926:CLOCK Proteins; C538944:Clock protein, mouse; D046988:Proteasome Endopeptidase Complex