Bernstein R M, Schluter S F, Lake D F, Marchalonis J J
College of Medicine, University of Arizona, Tucson 85724.
Biochem Biophys Res Commun. 1994 Nov 30;205(1):687-92. doi: 10.1006/bbrc.1994.2720.
A 700-bp fragment of the recombinase activating gene 1 (RAG-1) was cloned from several evolutionarily distant (sandbar shark, paddlefish, goldfish, axolotl and pig) species using PCR. The nucleotide and deduced amino acid sequences revealed a highly conserved region that has remained essentially unaltered during 400 million years of evolution; e.g., shark and human sequences were 75% identical at the nucleic acid level and 87% as protein. The RAG-1 mRNA levels in the shark were analyzed using semi-quantitative PCR to reveal expression patterns contrary to normal mammalian expression. These results establish that the genetic mechanisms for Ig gene rearrangement are present in all extant gnathanstomes.
利用聚合酶链式反应（PCR）从几种进化关系较远的物种（沙虎鲨、匙吻鲟、金鱼、美西螈和猪）中克隆出了重组激活基因1（RAG-1）的一个700碱基对的片段。核苷酸序列和推导的氨基酸序列显示出一个高度保守的区域，该区域在4亿年的进化过程中基本未发生改变；例如，鲨鱼和人类的序列在核酸水平上有75%的同一性，在蛋白质水平上有87%的同一性。使用半定量PCR分析了鲨鱼体内RAG-1 mRNA的水平，结果显示其表达模式与正常哺乳动物的表达模式相反。这些结果表明，免疫球蛋白（Ig）基因重排的遗传机制存在于所有现存的有颌类脊椎动物中。
