ISOLATION OF HUMAN AQUAPORIN-3 GENE

Human aquaporin 3 (AQP3) gene was isolated, and its structural organiz ation was characterized. The gene appeared to exist as a single copy i n the human genome and to comprise six exons distributing over 7 kilob ases. The sizes of the exons are 171, 127, 138, 119, 218, and 1035 bas e pairs, and those of introns are approximately 3530, 300, 350, 330, a nd 90 base pairs, respectively. The initiation site of transcription w as identified to locate 64 base pairs upstream of the first ATG codon by primer extension analysis and ribonuclease protection assay. The 5' -flanking region has a TATA box, two Sp1 sequences, and some consensus sequences including AP2 sites. With luciferase assay, the 5'-flanking region was demonstrated to have a promoter activity, which is up-regu lated 4-fold by phorbol ester. These findings about the genomic clone of human AQP3 will contribute to elucidate the molecular mechanism of transcriptional regulation of AQP3.