NEW LIGHT IS SHINING ON THE MELATONIN RHYTHM ENZYME - THE FIRST POSTCLONING VIEW

One of the most interesting molecules in circadian biology is serotoni n N-acetyltransferase (arylalkylamine N-acetyltransferase, AANAT), the enzyme that controls the daily rhythm in pineal melatonin production and blood melatonin. The recent cloning of AANAT cDNA has led to the c haracterization of the human gene; the realization that AANAT represen ts a unique gene family; the discovery of circadian rhythms in AANAT m RNA; the determination of the basis of transsynaptic and cellular regu lation of expression of the AANAT gene; a new understanding of the rel ationship of AANAT mRNA and activity; and the surprising finding of st rong expression of the AANAT gene in the retina and significant levels in select brain regions, the pituitary gland, and testes. The cloning of AANAT cDNA has not only made it possible to answer longstanding qu estions in circadian biology, but has also raised stimulating new issu es.