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Melatonin synthesis in retina: cAMP‐dependent transcriptional regulation of chicken arylalkylamine N ‐acetyltransferase by a CRE‐like sequence and a TTATT repeat motif in the proximal promoter
Author(s) -
Haque Rashidul,
Chong Nelson W.,
Ali Fatima,
Chaurasia Shyam S.,
Sengupta Trisha,
Chun Eugene,
Howell Jennifer C.,
Klein David C.,
Iuvone P. Michael
Publication year - 2011
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.2011.07397.x
Subject(s) - melatonin , acetyltransferase , biology , microbiology and biotechnology , chemistry , endocrinology , gene , biochemistry , acetylation
J. Neurochem. (2011) 119 , 6–17. Abstract Arylalkylamine N ‐acetyltransferase (AANAT) is the key regulatory enzyme controlling the daily rhythm of melatonin biosynthesis. In chicken retinal photoreceptor cells, Aanat transcription and AANAT activity are regulated in part by cAMP‐dependent mechanisms. The purpose of this study was to identify regulatory elements within the chicken Aanat promoter responsible for cAMP‐dependent induction. Photoreceptor‐enriched retinal cell cultures were transfected with a luciferase reporter construct containing up to 4 kb of 5′‐flanking region and the first exon of Aanat . Forskolin treatment stimulated luciferase activity driven by the ∼4 kb promoter construct and by all 5′‐deletion constructs except the smallest, Aanat (−217 to +120)luc. Maximal basal and forskolin‐stimulated expression levels were generated by the Aanat (−484 to +120)luc construct. This construct lacks a canonical cyclic AMP‐response element (CRE), but contains two other potentially important elements in its sequence: an eight times TTATT repeat (TTATT 8 ) and a CRE‐like sequence. Electrophoretic mobility shift assays, luciferase reporter assays, chromatin immunoprecipitation, and siRNA experiments provide evidence that these elements bind c‐Fos, JunD, and CREB to enhance basal and forskolin‐stimulated Aanat transcription. We propose that the CRE‐like sequence and TTATT 8 elements in the 484 bp proximal promoter interact to mediate cAMP‐dependent transcriptional regulation of Aanat .