Péléraux A, Karlsson L, Chambers J, Peterson P A
The R. W. Johnson Pharmaceutical Research Institute, Scripps Research Institute, IMM23, 10666 North Torrey Pines Road, La Jolla, CA 92037, USA.
Immunogenetics. 1996;43(4):204-14. doi: 10.1007/BF00587301.
The region encompassing the Ma, Mb1, Mb2, and Lmp2 genes of the mouse class II major histocompatibility complex (MHC) was sequenced. Since this region contains clusters of genes required for efficient class I and class II antigen presentation, it was interesting to search for putative additional genes in the 21 kilobase gap between the Mb1 and Lmp2 genes. Computer predictions of coding regions and CpG islands, exon trapping experiments, and cross-species comparison with the corresponding human sequence indicate that no additional functional gene is present in that stretch. However, computer analysis revealed the possible existence of an alternative 3' exon for Mb1. Except for the fact that the mouse MHC contains two Mb genes, the genomic organization of the H2-M loci was found to be almost identical to the organization of the human HLA-DM genes. The promoter regions of the Ma and Mb genes also resemble classical class II promoters, containing typical S, X, and Y boxes. Like the human genes, the three H2-M genes displayed very limited polymorphism when we compared the cDNA sequences from six haplotypes. Finally, comparison of DMB with Mb1 and Mb2, both at the genomic level and in their coding regions, suggests that the Mb gene was recently duplicated, probably only in certain rodents.
对小鼠Ⅱ类主要组织相容性复合体（MHC）中包含Ma、Mb1、Mb2和Lmp2基因的区域进行了测序。由于该区域包含有效进行Ⅰ类和Ⅱ类抗原呈递所需的基因簇，因此在Mb1和Lmp2基因之间21千碱基的间隔中寻找可能存在的其他基因很有意思。对编码区和CpG岛的计算机预测、外显子捕获实验以及与相应人类序列的跨物种比较表明，该区域不存在其他功能基因。然而，计算机分析揭示了Mb1可能存在一个替代性的3'外显子。除了小鼠MHC包含两个Mb基因这一事实外，发现H2-M基因座的基因组组织与人类HLA-DM基因的组织几乎相同。Ma和Mb基因的启动子区域也类似于经典的Ⅱ类启动子，包含典型的S、X和Y框。与人类基因一样，当我们比较来自六个单倍型的cDNA序列时，三个H2-M基因显示出非常有限的多态性。最后，在基因组水平及其编码区对DMB与Mb1和Mb2进行比较，表明Mb基因是最近复制的，可能仅在某些啮齿动物中发生。
