Gene structure and functional analysis of the human Na+/phosphate co-transporter.
Gene structure and functional analysis of the human Na+/phosphate co-transporter.
复制标题
人类钠/磷酸盐协同转运蛋白的基因结构和功能分析。
作者：
Y. Taketani;K. Miyamoto;K. Tanaka;K. Katai;M. Chikamori;S. Tatsumi;H. Segawa;H. Yamamoto;K. Morita;E. Takeda
从人基因组DNA文库中分离出三个包含Na+/磷酸盐共转运蛋白（NaPi-3）基因及其5'侧翼区的λ噬菌体克隆。该基因由13个外显子和12个内含子组成，跨度约为100 bp。14 kb。所有外显子-内含子连接都符合GT/AG规则。主要转录起始位点通过引物延伸分析确定，并且是第一外显子3'端上游57 bp的腺苷残基。在主要转录起始位点上游28 bp处有一个典型的TATA盒，5'侧翼区有多种顺式作用元件，包括cAMP反应元件、AP-1、AP-2和SP-1位点。该区域还包含三个直接重复样序列，类似于类固醇-甲状腺激素受体超家族成员（包括维生素D）的共有结合序列。缺失分析表明，5'侧翼区的nt-2409至nt-1259区域可能参与肾脏特异性基因表达。在与人维生素D受体表达载体共转染的COS-7细胞中也检测到NaPi-3启动子的维生素D响应性。NaPi-3启动子中三种维生素D受体应答元件的存在对于介导1，25-二羟基维生素D3增强的基因表达可能是重要的。
Three lambda phage clones encompassing the Na+/phosphate co-transporter (NaPi-3) gene and its 5' flanking region were isolated from a human genomic DNA library. The gene comprises 13 exons and 12 introns and spans approx. 14 kb. All exon-intron junctions conform to the GT/AG rule. The major transcription-initiation site was determined by primer-extension analysis and is an adenosine residue 57 bp upstream of the 3' end of the first exon. There is a typical TATA box 28 bp upstream of the major transcription-initiation site and various cis-acting elements, including a cAMP-responsive element, AP-1, AP-2 and SP-1 sites in the 5' flanking region. This region also contains three direct-repeat-like sequences that resemble the consensus binding sequence for members of the steroid-thyroid hormone receptor superfamily, including vitamin D. Deletion analysis suggests that the region from nt-2409 to nt-1259 in the 5' flanking region may be involved in kidney-specific gene expression. Vitamin D responsiveness of the NaPi-3 promoter was also detected in COS-7 cells co-transfected with a human vitamin D receptor expression vector. The presence of the three vitamin D receptor- responsive elements in the NaPi-3 promoter may be important in mediating the enhanced expression of the gene by 1,25-dihydroxyvitamin D3.