Gyllensten U B, Sundvall M, Erlich H A
Department of Medical Genetics, University of Uppsala, Sweden.
Proc Natl Acad Sci U S A. 1991 May 1;88(9):3686-90. doi: 10.1073/pnas.88.9.3686.
The loci encoding the class II cell surface antigens HLA-DR, -DQ, and -DP exhibit a remarkable degree of allelic polymorphism. Most of the class II allelic diversity is localized to the second exon, which encodes a beta-pleated sheet followed by an alpha-helical domain. Here, phylogenetic analysis of 39 human DRB1 alleles and 21 DRB1 alleles obtained by polymerase chain reaction (PCR) amplification from a set of closely related primates reveals that sequences encoding the beta-pleated sheet and those encoding the alpha-helix of the second domain have different evolutionary histories. The polymorphisms in the beta-pleated sheet have been conserved between species and appear to reflect the ancestral relationships among haplotypes, whereas polymorphic segments encoding the alpha-helical domain appear to have been inserted by interallelic sequence exchange into the framework of different ancestral DRB1 sequences. Allelic polymorphism at the DRB1 locus may thus have been generated in part by combining different variants of the two structural domains.
编码II类细胞表面抗原HLA - DR、- DQ和 - DP的基因座表现出显著程度的等位基因多态性。大多数II类等位基因多样性定位于第二个外显子，该外显子编码一个β折叠片层，其后是一个α螺旋结构域。在此，对39个人类DRB1等位基因以及通过聚合酶链反应（PCR）从一组亲缘关系密切的灵长类动物中扩增得到的21个DRB1等位基因进行系统发育分析，结果显示，编码β折叠片层的序列和编码第二个结构域α螺旋的序列具有不同的进化历史。β折叠片层中的多态性在物种间得以保留，似乎反映了单倍型之间的祖先关系，而编码α螺旋结构域的多态性片段似乎是通过等位基因间序列交换插入到不同祖先DRB1序列的框架中。因此，DRB1基因座的等位基因多态性可能部分是由两个结构域的不同变体组合产生的。
