[Transcriptional regulation of an enzyme involved in the synthesis of melatonin].
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.
Bernard
M
M
Laboratoire de Neurobiologie et Neuroendocrinologie Cellulaires, URA CNRS 290, Poitiers, France.
Guerlotte
J
J
Cogne
M
M
Greve
P
P
Collin
J P
JP
Voisin
P
P
D000121:Acetylserotonin O-Methyltransferase / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D002645:Chickens; D002940:Circadian Rhythm; D005786:Gene Expression Regulation; D008550:Melatonin / Q000096:biosynthesis*; D010870:Pineal Gland / Q000201:enzymology; D012333:RNA, Messenger / Q000032:analysis; D014158:Transcription, Genetic
D012333:RNA, Messenger; D000121:Acetylserotonin O-Methyltransferase; D008550:Melatonin
Régulation transcriptionnelle d'une enzyme impliquée dans la synthèse de mélatonine.