Cazzaniga G, Terao M, Lo Schiavo P, Galbiati F, Segalla F, Seldin M F, Garattini E
Molecular Biology Unit, Centro Catullo e Daniela Borgomainerio, Istituto di Ricerche Farmacologiche Mario Negri, Milano, Italy.
Genomics. 1994 Sep 15;23(2):390-402. doi: 10.1006/geno.1994.1515.
Xanthine dehydrogenase (XD) is a key enzyme in the catabolism of purines. A recently isolated XD cDNA clone (Terao et al., Biochem. J. 283, 863-870, 1992) was used to analyze the genomic structure and chromosomal location of this gene. XD was found to be a single-copy gene approximately 70 kb long with 36 exons containing the transcribed sequence. The length of the mouse XD gene was much longer and the structure more complex than those of the Drosophila and Calliphora homologs. The locus encoding the XD gene (designated Xd) was mapped to the distal part of mouse chromosome 17 by haplotype analysis of 114 interspecific backcross mice. Although Xd inactivation may be responsible for xanthinuria, a rare human genetic disease, this genetic locus is not a candidate for any previously described mouse mutation. The transcription start site was defined by primer extension and RNase mapping analysis, using liver mRNA. No other transcription start sites were identified in the liver and a variety of other organs after treatment with an interferon inducer. Transient transfection analysis in NIH3T3, tEnd, and COS cells with an appropriate reporter gene demonstrated that a functional promoter is located within the first 268 bp preceding the transcriptional initiation site.
黄嘌呤脱氢酶（XD）是嘌呤分解代谢中的关键酶。最近分离得到的一个XD cDNA克隆（Terao等人，《生物化学杂志》283卷，863 - 870页，1992年）被用于分析该基因的基因组结构和染色体定位。结果发现XD是一个单拷贝基因，长度约为70 kb，含有36个外显子，包含转录序列。小鼠XD基因的长度比果蝇和丽蝇的同源基因长得多，结构也更复杂。通过对114只种间回交小鼠进行单倍型分析，将编码XD基因的位点（命名为Xd）定位到小鼠17号染色体的远端。尽管Xd失活可能是人类罕见遗传病黄嘌呤尿症的病因，但该基因位点并非任何先前描述的小鼠突变的候选基因。利用肝脏mRNA，通过引物延伸和核糖核酸酶图谱分析确定了转录起始位点。在用干扰素诱导剂处理后，在肝脏和其他多种器官中未发现其他转录起始位点。用合适的报告基因在NIH3T3、tEnd和COS细胞中进行瞬时转染分析表明，一个功能性启动子位于转录起始位点之前的前2
