DNA elements of the type 1 adenylyl cyclase gene locus enhance reporter gene expression in neurons and pinealocytes

The Ca2+-stimulated type 1 adenylyl cyclase (AC1) contributes to several fo rms of synaptic plasticity and is the only known neurospecific adenylyl cyc lase. Furthermore, the protein and mRNA levels of AC1 undergo a circadian o scillation in the pineal gland, and AC1 may play a pivotal role in regulati ng nocturnal melatonin synthesis. To better understand the expression of AC 1, we isolated mouse genomic DNA clones of AC1, The transcription and trans lation start regions of mouse ACI share extensive homologies with the bovin e counterpart. The upstream proximal region has potential binding sites for transcription factors, including the steroid receptor family, the E-box fa ctors, and Sp1. A 280-bp fragment that contains the transcription start sit e directed reporter gene expression in cultured cortical neurons and pineal ocytes functioning as a basal neuro- and pineal-directed promoter. Interest ingly, pinealocyte expression of the reporter gene was inhibited by increas es in cAMP, This cAMP sensitivity may explain why AC1 mRNA in the pineal is low at night when cAMP is elevated and high during the day when cAMP signa ls drop. An adjacent 330-bp fragment interacted specifically with nuclear f actor(s) that we designate binary E-box factor (BEF). Methylation interfere nce and DNase I footprinting identified the BEF-binding site sequence as 5' -CCAAGGTCACGTGGC-3'. When linked to the basal tissue-directed promoter, thi s 15-bp sequence further enhanced reporter expression in neurons and pineal ocytes. We propose that this 15-bp sequence may contribute to increased exp ression of AC1 in neurons and pinealocytes relative to other cells.