Is light-regulated AP-1 binding in the rat suprachiasmatic nucleus gated by the circadian clock?
In mammals, photic entrainment of circadian rhythms likely involves light- and clock-dependent expression of immediate early genes, including fos-like and jun-like genes, in the rat suprachiasmatic nucleus. Using an electrophoretic mobility shift assay, we evaluated whether the photic regulation of DNA-binding activity and composition of activating protein-1 (AP-1) complexes in the suprachiasmatic nucleus is also dependent on circadian phase. Phase-dependent light inducibility in the expression of fra-2 and c-fos genes and in immunoreactive Fra-2 and c-Fos protein expression was also evaluated, by in situ hybridization and immunocytochemistry. Light's effects on AP-1 DNA-binding differed both qualitatively and quantitatively according to the circadian phase at which light was applied. This phase dependence accounted for by both compartmentalization of proteins involved in constitutive AP-1 complexes within the nucleus or cytoplasm and control of the extent to which the expression of specific complexes was induced. It was then shown that the mechanisms by which the circadian clock gates the photic induction of AP-1 components differed according to the nature of the protein.
François-Bellan
A M
AM
INSERM U-501, Institut Fédératif Jean-Roche, Faculté de Médecine Nord, Université de la Méditerranée, Bd. Pierre Dramard, 13916 Marseille cedex 20, France. francois.am@jean-roche.univ-mrs.fr
Guillaumond
F
F
Bosler
O
O
Becquet
D
D
D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000235:genetics; D051921:Fos-Related Antigen-2; D015870:Gene Expression / Q000502:physiology; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008297:Male; D010775:Photic Stimulation; D011485:Protein Binding / Q000235:genetics; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D013493:Suprachiasmatic Nucleus / Q000737:chemistry* / Q000502:physiology*; D018808:Transcription Factor AP-1 / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics
D004268:DNA-Binding Proteins; D051921:Fos-Related Antigen-2; C497874:Fosl2 protein, rat; D016760:Proto-Oncogene Proteins c-fos; D012333:RNA, Messenger; D018808:Transcription Factor AP-1; D014157:Transcription Factors