Figure 1.

The main regulatory element in the promoter of calcitonin gene-related polypeptide alpha (CALCA) is an 18-bp enhancer, which is a part of a distal cell-specific complex helix–loop–helix (HLH) enhancer. The HLH motif of the 18-bp enhancer overlaps with a forkhead (FOX) motif and is targeted by heterotrimer upstream stimulatory factor (USF)-1 and -2 and the cell-specific forkhead box A2 protein (FOXA2). The promoter also contains a proximal cAMP-responsive element (CRE) and a Ras responsive element (RRE) targeted by the cyclic adenosine monophosphate (cAMP) response element-binding protein (CREB) and related proteins (RPs). Approximate positions of these two elements, upstream of the transcription start site (TSS), are indicated. The CALCA promoter contains both cell-specific and non-cell-specific elements as well as CpG dinucleotides contributing to functional CpG islands not presented here.