Genomic structure of the regulatory region of the voltage-gated calcium channel α1D

In excitable and endocrine organs, calcium influxes through the L-type voltage-gated calcium channel (VGCC) which is composed of four (alpha 1, alpha 2, beta, and gamma) subunits. Temporal and spatial expression of calcium channel activity is regulated by the transcription of alpha 1 subunit. To elucidate the genomic organization of the VGCC alpha 1D subunit gene, a genomic clone was isolated from the human genomic library and its sequence was analyzed. A 12 kb genomic clone contained the 5'-flanking regulatory region and first two exons was selected and the initiation site for alpha 1D mRNA synthesis was examined by primer extension analysis. The major initiation site was found at the -523 NT position in the translation initiation site. The TATA box could not be found above the transcription initiation site. The CAT vector construct containing the 2.5 kb upstream region had high CAT activity on transfection to NG108-15 and PC12 cells, which confers the neuronal expression of the alpha 1D gene.