Molecular cloning of the arylalkylamine-N-acetyltransferase and daily variations of its mRNA expression in the Syrian hamster pineal gland.
The arylalkylamine-N-acetyltransferase (AA-NAT) expressed in the vertebrate pineal gland catalyzes the N-acetylation of the serotonin into N-acetylserotonin and is considered to be the rate limiting enzyme of the pineal melatonin synthesis. Indeed, dramatic changes in its activity throughout the 24-h period drive the large day/night variations in plasma melatonin concentrations. Recently, AA-NAT was cloned in the rat pineal. In this species, AA-NAT mRNA variations were demonstrated to be responsible of the well known AA-NAT activity and plasma melatonin circadian fluctuations. In the Syrian hamster, the pineal melatonin secretion pattern is characterized by a late-night short-duration peak of melatonin synthesis. We investigated whether this typical pattern could be due to a late-night delayed pineal AA-NAT mRNA expression. The first part of our study was dedicated to the molecular cloning of a Syrian hamster AA-NAT cDNA. A PCR-generated clone of 1045 bp encoding the AA-NAT has been isolated and sequenced. In situ hybridization using an AA-NAT cRNA probe revealed that the AA-NAT mRNA expression undergoes strong daily fluctuations in the Syrian hamster pineal, with undetectable level in the second half of the light period and a dramatic increase at night. After lights off, the AA-NAT mRNA expression requires 6-7 h to reach its maximum expression. This result thus suggests that the transcription of the AA-NAT mRNA in the Syrian pineal gland determines the lag period in pineal responsiveness and melatonin synthesis to darkness.
Gauer
F
F
Neurobiologie des Fonctions Rythmiques et Saisonnières, CNRS-UMR 7518, Université Louis Pasteur, 12 rue de l'Université, 67000, Strasbourg, France. gauer@neurochem.u-strasbg.fr
Poirel
V J
VJ
Garidou
M L
ML
Simonneaux
V
V
Pévet
P
P
D000595:Amino Acid Sequence; D000818:Animals; D001191:Arylamine N-Acetyltransferase / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics*; D001483:Base Sequence; D020134:Catalytic Domain; D002940:Circadian Rhythm; D003001:Cloning, Molecular; D006224:Cricetinae; D018076:DNA, Complementary; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D008647:Mesocricetus; D008969:Molecular Sequence Data; D010870:Pineal Gland / Q000201:enzymology*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012756:Sheep; D013997:Time Factors; D014158:Transcription, Genetic
D018076:DNA, Complementary; D012333:RNA, Messenger; D011994:Recombinant Proteins; D001191:Arylamine N-Acetyltransferase