Differential expression of activator protein-1 proteins in the pineal gland of Syrian hamster and rat may explain species diversity in arylalkylamine N-acetyltransferase gene expression.
Species differences have been reported for the nighttime regulation of arylalkylamine N-acetyltransferase (AA-NAT), the melatonin rhythm-generating enzyme. In particular, de novo synthesis of stimulatory transcription factors is required for Aa-nat transcription in the Syrian hamster but not in the rat pineal gland. The present work investigated the contribution of phosphorylated cAMP-responsive element-binding protein, c-FOS, c-JUN, and JUN-B in the regulation of Aa-nat transcription in Syrian hamsters compared with rats. The nighttime pattern of cAMP-responsive element-binding protein phosphorylation and regulation by norepinephrine observed in the Syrian hamster was similar to those reported in the rat. On the contrary, strong divergences in c-FOS, c-JUN, and JUN-B expression were observed between both species. In Syrian hamster, predominant expression of c-FOS and c-JUN was observed at the beginning of night, whereas a predominant expression of c-JUN and JUN-B was observed in the late night in rat. The early peak of c-FOS and c-JUN, known to form a stimulatory transcription dimer, suggests that they are involved in the nighttime stimulation of Aa-nat transcription. Indeed, early-night administration of a protein synthesis inhibitor (cycloheximide) markedly decreased AA-NAT mRNA levels in Syrian hamster. In the rat, high levels of JUN-B and c-JUN, constituting an inhibitory transcription dimer, are probably involved in the late-night inhibition of Aa-nat transcription. Early-night administration of cycloheximide actually increased AA-NAT mRNA levels toward the late night. Therefore, composition and timing of the pineal activator protein-1 complexes differ between rat and Syrian hamster and may be an activator (Syrian hamster) or an inhibitor (rat) of Aa-nat transcription.
Sinitskaya
Natalia
N
Institut des Neurosciences Cellulaires et Intégratives, Département de Neurobiologie des Rythmes, UMR-7168/LC2 CNRS-Université Louis Pasteur, 5 rue Blaise Pascal, 67084 Strasbourg Cedex, France.
Salingre
Anthony
A
Klosen
Paul
P
Revel
Florent G
FG
Pévet
Paul
P
Simonneaux
Valérie
V
D000818:Animals; D001191:Arylamine N-Acetyltransferase / Q000235:genetics*; D006224:Cricetinae; D017362:Cyclic AMP Response Element-Binding Protein / Q000032:analysis*; D003513:Cycloheximide / Q000494:pharmacology; D005260:Female; D008297:Male; D008647:Mesocricetus; D010870:Pineal Gland / Q000737:chemistry*; D016760:Proto-Oncogene Proteins c-fos / Q000032:analysis*; D016755:Proto-Oncogene Proteins c-jun / Q000032:analysis*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D011941:Receptors, Adrenergic / Q000502:physiology; D013045:Species Specificity
D017362:Cyclic AMP Response Element-Binding Protein; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D012333:RNA, Messenger; D011941:Receptors, Adrenergic; D003513:Cycloheximide; D001191:Arylamine N-Acetyltransferase