title: Evidence for an overlapping role of CLOCK and NPAS2 transcription factors in liver circadian oscillators.
abstract: The mechanisms underlying the circadian control of gene expression in peripheral tissues and influencing many biological pathways are poorly defined. Factor VII (FVII), the protease triggering blood coagulation, represents a valuable model to address this issue in liver since its plasma levels oscillate in a circadian manner and its promoter contains E-boxes, which are putative DNA-binding sites for CLOCK-BMAL1 and NPAS2-BMAL1 heterodimers and hallmarks of circadian regulation. The peaks of FVII mRNA levels in livers of wild-type mice preceded those in plasma, indicating a transcriptional regulation, and were abolished in Clock(-/-); Npas2(-/-) mice, thus demonstrating a role for CLOCK and NPAS2 circadian transcription factors. The investigation of Npas2(-/-) and Clock(Delta19/Delta19) mice, which express functionally defective heterodimers, revealed robust rhythms of FVII expression in both animal models, suggesting a redundant role for NPAS2 and CLOCK. The molecular bases of these observations were established through reporter gene assays. FVII transactivation activities of the NPAS2-BMAL1 and CLOCK-BMAL1 heterodimers were (i) comparable (a fourfold increase), (ii) dampened by the negative circadian regulators PER2 and CRY1, and (iii) abolished upon E-box mutagenesis. Our data provide the first evidence in peripheral oscillators for an overlapping role of CLOCK and NPAS2 in the regulation of circadianly controlled genes.
authors.affiliation: Dipartimento di Biochimica e Biologia Molecolare, Università di Ferrara, Via Fossato di Mortara 74, 44100 Ferrara, Italia. pnm@unife.it
authors.forename: Cristiano
authors.initials: C
authors.lastname: Bertolucci
authors.forename: Nicola
authors.initials: N
authors.lastname: Cavallari
authors.forename: Ilaria
authors.initials: I
authors.lastname: Colognesi
authors.forename: Jacopo
authors.initials: J
authors.lastname: Aguzzi
authors.forename: Zheng
authors.initials: Z
authors.lastname: Chen
authors.forename: Pierpaolo
authors.initials: P
authors.lastname: Caruso
authors.forename: Augusto
authors.initials: A
authors.lastname: Foá
authors.forename: Gianluca
authors.initials: G
authors.lastname: Tosini
authors.forename: Francesco
authors.initials: F
authors.lastname: Bernardi
authors.forename: Mirko
authors.initials: M
authors.lastname: Pinotti
mesh_terms: D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000502:physiology*; D056926:CLOCK Proteins; D018797:Cell Cycle Proteins / Q000378:metabolism; D002940:Circadian Rhythm / Q000502:physiology*; D056931:Cryptochromes; D024721:E-Box Elements; D005167:Factor VII / Q000235:genetics / Q000378:metabolism; D005420:Flavoproteins / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000502:physiology*; D009687:Nuclear Proteins / Q000378:metabolism; D056950:Period Circadian Proteins; D012333:RNA, Messenger / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology*; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D056926:CLOCK Proteins; D018797:Cell Cycle Proteins; D056931:Cryptochromes; D005167:Factor VII; D005420:Flavoproteins; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D056950:Period Circadian Proteins; D012333:RNA, Messenger; D015534:Trans-Activators; D014157:Transcription Factors; C538964:Cry1 protein, mouse; C491259:Npas2 protein, mouse; C513312:Per2 protein, mouse; C538944:Clock protein, mouse