title: Time-of-day- and light-dependent expression of ubiquitin protein ligase E3 component N-recognin 4 (UBR4) in the suprachiasmatic nucleus circadian clock.
abstract: Circadian rhythms of behavior and physiology are driven by the biological clock that operates endogenously but can also be entrained to the light-dark cycle of the environment. In mammals, the master circadian pacemaker is located in the suprachiasmatic nucleus (SCN), which is composed of individual cellular oscillators that are driven by a set of core clock genes interacting in transcriptional/translational feedback loops. Light signals can trigger molecular events in the SCN that ultimately impact on the phase of expression of core clock genes to reset the master pacemaker. While transcriptional regulation has received much attention in the field of circadian biology in the past, other mechanisms including targeted protein degradation likely contribute to the clock timing and entrainment process. In the present study, proteome-wide screens of the murine SCN led to the identification of ubiquitin protein ligase E3 component N-recognin 4 (UBR4), a novel E3 ubiquitin ligase component of the N-end rule pathway, as a time-of-day-dependent and light-inducible protein. The spatial and temporal expression pattern of UBR4 in the SCN was subsequently characterized by immunofluorescence microscopy. UBR4 is expressed across the entire rostrocaudal extent of the SCN in a time-of-day-dependent fashion. UBR4 is localized exclusively to arginine vasopressin (AVP)-expressing neurons of the SCN shell. Upon photic stimulation in the early subjective night, the number of UBR4-expressing cells within the SCN increases. This study is the first to identify a novel E3 ubiquitin ligase component, UBR4, in the murine SCN and to implicate the N-end rule degradation pathway as a potential player in regulating core clock mechanisms and photic entrainment.
authors.affiliation: Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada.
authors.forename: Harrod H
authors.initials: HH
authors.lastname: Ling
authors.affiliation: Ottawa Institute of Systems Biology and Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Christian
authors.initials: C
authors.lastname: Beaulé
authors.affiliation: Ottawa Institute of Systems Biology and Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Cheng-Kang
authors.initials: CK
authors.lastname: Chiang
authors.affiliation: Ottawa Institute of Systems Biology and Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Ruijun
authors.initials: R
authors.lastname: Tian
authors.affiliation: Ottawa Institute of Systems Biology and Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Daniel
authors.initials: D
authors.lastname: Figeys
authors.affiliation: Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada; Ottawa Institute of Systems Biology and Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Hai-Ying M
authors.initials: HY
authors.lastname: Cheng
mesh_terms: D000818:Animals; D002148:Calmodulin-Binding Proteins; D002460:Cell Line; D057906:Circadian Clocks / Q000235:genetics*; D002940:Circadian Rhythm / Q000235:genetics; D005786:Gene Expression Regulation; D008027:Light; D008297:Male; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D009474:Neurons / Q000378:metabolism; D010455:Peptides / Q000235:genetics / Q000378:metabolism; D017440:Photoperiod; D011485:Protein Binding; D021381:Protein Transport; D020543:Proteome; D040901:Proteomics / Q000379:methods; D015203:Reproducibility of Results; D013493:Suprachiasmatic Nucleus / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
chemical_list: D002148:Calmodulin-Binding Proteins; D008869:Microtubule-Associated Proteins; D010455:Peptides; D020543:Proteome; D044767:Ubiquitin-Protein Ligases; C528904:Ubr4 protein, mouse
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