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Molecular mechanism underlying the light-dependent resetting of the circadian clock and activation of locomotor activities

original title of the thesis: Light-dependent and circadian clock-regulated activation of sterol regulatory element-binding protein, X-box-binding protein 1, and heat shock factor pathways
(Proc. Natl. Acad. Sci. USA, 108(12), 4864-4869, 2011)

The circadian clock is phase delayed or advanced by light when given at early or late night, respectively. Despite the importance of the time-of-day-dependent phase-responses to light, the underlying molecular mechanism is poorly understoo. Here we found that SREBP transcription factor, which regulates a large group of cholesterol biosynthetic genes, activated transcription of E4Bp4, a key regulator in the phase-delaying mechanism of the chicken pineal clock, in response to a light pulse given at early night. Furthermore, we revealed that light-activated SREBP stimulated production and release of a neurosteroid 7α-hydroxypregnenolone in the pineal gland, resulting in the activation of locomotor activities of chicks. These results demonstrate a novel endocrine function of the pineal gland, which has been known to release sleep-related hormone melatonin.