Chromosome mapping of genes in mammals and birds and its applcation for animal resource sciences

已有报道通过功能互补在大肠杆菌和酵母中克隆了三功能的甘氨酰胺核糖核苷酸合成酶(GARS)-氨基咪唑核糖核苷酸合成酶(AIRS)-甘氨酰胺核糖核苷酸转换酶(GART)的编码基因。在这项研究中，我们利用人GARS-AIRS-GART基因的5‘端区域作为探针，从人胎脑cDNA文库中分离到一个仅编码GARS结构域的新的cDNA克隆。核苷酸序列分析表明，该cDNA的编码区与GARS-AIRS-GART基因的GARS结构域的编码区完全相同。对这两个转录本在不同年龄的正常人脑中的表达模式分析表明，每个转录本的转录水平都随着年龄的不同而不同。我们的结论是，人类GARS-AIRS-GART基因产生三功能酶，编码GARS结构域的人类基因产生仅显示GARS活性的酶，此外，GARS-AIRS-GART基因中GARS和AIRS的连接区在灵长类之间保存完整。相反，在GARS基因的3‘非翻译区，我们观察到人类和其他灵长类动物之间有一些核酸的替换、插入和缺失。综上所述，这些结果有力地表明GARS-AIRS-GART基因是从独立的GARS、AIRS、GART基因进化融合而来的。利用染色体作图技术，我们打算继续分析动物资源科学的其他重要基因。

Cloning of a human cDNA encoding the trifunctional glycinamide ribonucleotide synthetase (GARS) -aminoimidazole ribonucleotide synthetase (AIRS) -glycinamide ribonucleotide transformylase (GART) enzyme by functional complementation in E.coli and in yeast has been reported previously. In this study, we demonstrates the isolation of a novel cDNA clone encoding only the GARS domain from a human fetal brain cDNA library using the 5' region of the human GARS-AIRS-GART cDNA as a probe. Analysis of the nucleotide sequence reveals that the coding region of this cDNA is identical to that of the GARS domain of the GARS-AIRS-GART gene cDNA.Analysis of the expression patterns of the two transcripts in normal human brains of various ages demonstrates that each is transcribed at different overall levels depending upon age. We concluded that the human GARS-AIRS-GART gene produces the trifunctional enzyme and the human gene encoding only the GARS domain produced the enzyme showing the activity of only GARS.In addition, the connecting region of GARS and AIRS in the GARS-AIRS-GART gene were completely preserved between the primates. On the contrary, in the 3' untranslate region of the GARS gene we observed a few replacements, inserts as well as deletion of nucleic acids between human and other primates. In conclusion, these results strongly suggested that the GARS-AIRS-GART gene is fused from the independent GARS,AIRS,GART genes evolutionally. Using the chromosome mapping techniques, we continuously intend to analyze other important genes for animal resource sciences.