Characterization of the mouse A3 adenosine receptor gene: exon/intron organization and promoter activity.

In a previous study, we reported the expression of A3 adenosine receptor mRNA in rat vascular smooth muscle cells (VSMC) and demonstrated that its levels affect the intracellular concentration of cAMP. In the current study, we isolated the mouse A3 adenosine receptor (A3AR) gene, characterized its structure, and defined its promoter activity in VSMC. The mouse A3AR gene fragment available to us has 3 kb of coding sequences, composed of two exons separated by a single intron, and 2.3 kb of 5' noncoding region. The promoter region lacks "TATA" and "CAAT" boxes, but contains an initiator consensus sequence. In accordance with Northern blot analysis of A3AR mRNA, transient transfection experiments showed that the promoter activity of this fragment was significant in VSMC and astrocytes and high in mast cells. The characterization of the mouse A3 adenosine receptor gene and insight into its promoter region will allow further studies to determine the physiological importance of its transcriptional regulation in different tissues.