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Title: [Transcriptional regulation of an enzyme involved in the synthesis of melatonin]. Author: Bernard M, Guerlotte J, Cogne M, Greve P, Collin JP, Voisin P. Journal: C R Seances Soc Biol Fil; 1993; 187(1):69-76. PubMed ID: 8242424. Abstract: The indolic hormone melatonin is produced by the pineal gland according to a daily rhythm. The terminal step of melatonin synthesis is catalyzed by hydroxyindole-O-methyltransferase (HIOMT, EC 2.1.1.4). Adaptation to constant light or darkness modifies HIOMT activity and concentration. Using a cDNA probe encoding HIOMT, we investigated the effect of environmental lighting on HIOMT gene expression in the chicken pineal gland. HIOMT mRNA levels increased by 100% in constant light as compared with constant darkness. In addition, the present study disclosed the existence of a day/night rhythm of HIOMT gene transcription, with 3-fold higher mRNA levels at midday than at midnight. Unexpected darkness did not prevent the daytime rise in HIOMT mRNA levels, whereas unexpected light prevented the night-time fall in HIOMT mRNA levels. Together, the data would suggest that the day/night rhythm of HIOMT gene transcription in the chicken pineal gland involves both a response to light and the activity of a biological oscillator.[Abstract] [Full Text] [Related] [New Search]