Morooka A, Asahina M, Kohda C, Tajima S, Niimi M, Nishino Y, Sugiyama M, Aida Y
Laboratory of Gene Technology and Safety, Tsukuba Life Science Center, Institute of Physical and Chemical Research (RIKEN), Ibaraki, Japan.
Biochem Biophys Res Commun. 1995 Jul 6;212(1):110-7. doi: 10.1006/bbrc.1995.1943.
cDNA clones encoding the bovine major histocompatibility complex (MHC) class II DQ alpha chain were isolated. One clone, MQ9, encoded a primary translated product of 255 amino acids, with a signal peptide of 23 amino acids and a mature polypeptide of 232 amino acids. A new A2 gene in the DQ subregion of the bovine genome was identified from a comparison of amino acid sequences encoded by class II A genes among several species and the construction of a phylogenetic tree. It was revealed that MQ9 is most closely related to the ovine DQA2 genes among sequences from various mammalian species. By contrast, the BoLA-DQA genes previously isolated are more closely related to ovine DQA1 than to the BoLA-DQA2 gene, and they represent BoLA-DQA1 genes. Thus, the presence of two BoLA A genes, which may be expressed and functional in the bovine, as well as in sheep was confirmed. A large number of amino acids unique to products of DQA2 genes of bovine and ovine origin were identified when the predicted amino acid sequences for both species were compared, and most of the DQA2-specific residues were located in the alpha 1 domain and were conserved with respect to products of DQA1 genes of ruminants. Thus, several characteristics of the bovine DQA genes were found to differ from those of human and rodent genes, despite similarities in gene structure and in nucleotide sequence.
分离出了编码牛主要组织相容性复合体（MHC）Ⅱ类DQα链的cDNA克隆。其中一个克隆MQ9编码一个由255个氨基酸组成的初级翻译产物，带有一个23个氨基酸的信号肽和一个232个氨基酸的成熟多肽。通过比较几个物种中Ⅱ类A基因编码的氨基酸序列并构建系统发育树，在牛基因组的DQ亚区域中鉴定出一个新的A2基因。结果表明，在各种哺乳动物物种的序列中，MQ9与绵羊DQA2基因关系最为密切。相比之下，先前分离的BoLA - DQA基因与绵羊DQA1的关系比与BoLA - DQA2基因的关系更密切，它们代表BoLA - DQA1基因。因此，证实了牛和绵羊中可能存在两个可表达且有功能的BoLA A基因。当比较这两个物种的预测氨基酸序列时，鉴定出了大量牛和绵羊来源的DQA2基因产物特有的氨基酸，并且大多数DQA2特异性残基位于α1结构域，并且相对于反刍动物的DQA1基因产物是保守的。因此，尽管牛DQA基因在基因结构和核苷酸序列上有相似之处，但发现其几个特征与人类和啮齿动物的基因不同。
