Verhoeven A J, Roos M H, Ploegh H L
Department of Biochemistry I, Erasmus University, Rotterdam, The Netherlands.
Immunogenetics. 1988;28(6):406-11. doi: 10.1007/BF00355371.
A genomic library was constructed from DNA of a domestic cat and screened with a human HLA-DR alpha probe at low stringency. Several positive clones were isolated, and the DNA sequence of one of these clones was determined. Comparison with class II alpha gene sequences from other species suggested that the feline gene is a DPA homologue (FLA-DPA) showing 84% similarity with HLA-DP alpha 1 in the exon encoding the second domain. The FLA-DPA gene that was isolated is a pseudogene, as two frame-shift mutations are present: one in the exon encoding the second domain, causing premature termination of translation, and one in the exon encoding the transmembrane region. The latter mutation and the further deletion of two codons in the transmembrane exon show a remarkable resemblance to the same exon of the human pseudogene, HLA-DPA2. Hence, both pseudogenes evolved from the same ancestral gene. The inactivation of this DPA gene could therefore have occurred prior to the major mammalian divergence.
从家猫的DNA构建了一个基因组文库，并用人类HLA - DRα探针在低严谨度条件下进行筛选。分离出了几个阳性克隆，并确定了其中一个克隆的DNA序列。与其他物种的II类α基因序列比较表明，猫科动物基因是一个DPA同源物（FLA - DPA），在编码第二个结构域的外显子中与HLA - DPα1显示出84%的相似性。分离出的FLA - DPA基因是一个假基因，因为存在两个移码突变：一个在编码第二个结构域的外显子中，导致翻译提前终止，另一个在编码跨膜区域的外显子中。后一个突变以及跨膜外显子中两个密码子的进一步缺失与人类假基因HLA - DPA2的同一外显子有显著相似性。因此，这两个假基因都从同一个祖先基因进化而来。所以，这个DPA基因的失活可能发生在主要哺乳动物分化之前。
