Molecular, cellular and in vivo analyses of photoresponses and circadian rhythms in animals

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(1)Activation of Gil induced a phase-shift of the chick pineal circadian clock in a manner similar to that induced by light. In the promoter region of pinopsin gene, we identified a light-responsive element responsible for its light-dependent transcriptional activation.(2)Farnesylation of retinal rod G-protein transducin plays an important role in not only the cellular light-signaling but also the light-adaptation. We found that GRK7-1 expressed in the zebrafish retinal cones shows opsin-phosphorylating activity dozens-fold higher than that of rod-specific GRK1A.(3)Chick pineal and frog retinal MAPK was circadian-activated showing the peak activity at night. Within the mouse SCN, the profiles of the temporal and light activation of MAPK are both different between the dorsomedial and central regions of the SCN. We identified amino acid residues in BMAL1, CRY1 and CRY2 to be phosphorylated by MAPK and their phosphorylation-dependent functional changes. We also found that SCOP expressed abundantly in the SCN is a negative regulator of K-Ras and downstream MAPK. It was shown that p38 MAPK regulates the molecular clock in the daytime to have the phase-advancing effect.(4)When the chicks entrained to 12L : 12D conditions were exposed to prolonged light extending into the early night, pineal E4BP4 protein was kept at a high level, which delayed the morning induction of Per2 and delayed the phase of the pineal clock. E4BP4 was phosphorylated by CKIε, leading to its proteasomal degradation.(5)We found that glucose-stimulation of rat-1 cells resets the clock by a mechanism to which Tieg 1 and Vdup 1 contribute. TIEG 1 protein was in fact up-regulated upon glucose administration and it directly acts on the promoter of Bmall to inhibit the transcription.(6)Within the promoter region of pineal opsin exorhodopsin gene, we identified a cis-acting element, PIPE, that drives pineal-specific gene expression in the zebrafish.