Light‐Induced Variations in AP‐1 Binding Activity and Composition in the Rat Suprachiasmatic Nucleus

• Published in: Journal of neurochemistry 1999-02, Vol.72 (2), p.841-847
• Main Authors: François‐Bellan, A. M., Deprez, P., Becquet, D.
• Format: Article
• Language: English
• Subjects: Activating protein‐1; Animals; Biological and medical sciences; Biological Clocks - physiology; Chronobiology; DNA-Binding Proteins - analysis; DNA-Binding Proteins - biosynthesis; DNA-Binding Proteins - metabolism; Electrophoretic mobility shift assay; Fos-Related Antigen-2; Fundamental and applied biological sciences. Psychology; Immunocytochemistry; Immunohistochemistry; Life Sciences; Male; Neurobiology; Neurons and Cognition; Photic regulation; Photic Stimulation; Protein Binding - physiology; Proto-Oncogene Proteins c-fos - biosynthesis; Rat; Rats; Rats, Sprague-Dawley; Suprachiasmatic nucleus; Suprachiasmatic Nucleus - chemistry; Suprachiasmatic Nucleus - metabolism; Transcription Factor AP-1 - analysis; Transcription Factor AP-1 - biosynthesis; Transcription Factor AP-1 - metabolism; Transcription Factors - analysis; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Visual Pathways - chemistry; Visual Pathways - metabolism
• ISSN: 0022-3042; 1471-4159
• DOI: 10.1046/j.1471-4159.1999.0720841.x

: Expression of immediate early genes, including fos‐like and jun‐like genes, in the suprachiasmatic nucleus is believed to be part of the mechanism for photic entrainment of circadian rhythms to the environmental light/dark cycle. However, the effects of a light stimulus on activating protein‐1 (AP‐1) complexes in the suprachiasmatic nucleus remain unclear. The photic regulation of AP‐1 DNA‐binding activity and composition in the rat suprachiasmatic nucleus was evaluated by using an electrophoretic mobility shift assay. A light pulse given during subjective night induced an increase in AP‐1 binding activity when either nuclear or whole‐cell extracts from suprachiasmatic nuclei were used. Under constant dark conditions, proteins that are predominant components of AP‐1 complexes are Fra‐2 and Jun‐D. Under light stimulation, c‐Fos and Jun‐B consistently increased, as expected, but this was also the case for Fra‐2, Jun‐D, and c‐Jun, although to a lesser extent. An immunocytochemical study of the Fra‐2 expression pattern demonstrated the presence of the protein in the ventrolateral as well as in the dorsomedial subdivisions of the suprachiasmatic nucleus. Light regulation of Fra‐2 immunoreactivity, however, appeared to be restricted to the ventrolateral subdivision. It is concluded that light may be acting both by increasing constitutive AP‐1 complexes and by inducing the expression of specific complexes.