Kodaira M, Kinashi T, Umemura I, Matsuda F, Noma T, Ono Y, Honjo T
J Mol Biol. 1986 Aug 20;190(4):529-41. doi: 10.1016/0022-2836(86)90239-1.
We have isolated 23 different cosmid clones of the heavy-chain variable region genes (VH) of human immunoglobulin. These clones encompass about 1000 X 10(3) base-pairs of DNA containing 61 VH genes. Characterization of the 23 clones by Southern blot hybridization showed that VH genes belonging to different families were physically linked in many regions. Cluster 71, which was analyzed in detail, comprised seven VH segments arranged in the same orientation with different intervals. This clone contained internal homology regions, each carrying two VH segments of different families. Comparison of the nucleotide sequences of VH segments within each family showed that profiles of accumulation of mutations in framework (FR) and complementarity-determining (CDR) regions were different. CDR had more mutations at amino-acid-substituting positions than at silent positions, whereas FR had the reverse distribution of mutations. Five out of seven VH segments of this cluster were pseudogenes containing various mutations. VH pseudogenes were classified into two distinct groups; one with a few replacement mutations (conserved pseudogenes), and the other with rather extensive mutations (diverged pseudogenes). The possibility that conserved pseudogenes serve as a reservoir of VH segments is discussed.
我们已经分离出23个不同的人免疫球蛋白重链可变区基因（VH）的黏粒克隆。这些克隆包含约1000×10³碱基对的DNA，其中含有61个VH基因。通过Southern印迹杂交对这23个克隆进行表征，结果表明属于不同家族的VH基因在许多区域在物理上是连锁的。对详细分析的71号簇进行分析，发现其由七个VH区段组成，这些区段以相同方向排列，间隔不同。该克隆包含内部同源区域，每个区域携带两个不同家族的VH区段。对每个家族内VH区段的核苷酸序列进行比较，结果表明框架（FR）区和互补决定（CDR）区的突变积累模式不同。CDR在氨基酸替换位点的突变比在沉默位点的多，而FR的突变分布则相反。该簇的七个VH区段中有五个是含有各种突变的假基因。VH假基因可分为两个不同的组；一组有一些替换突变（保守假基因），另一组有相当广泛的突变（分化假基因）。文中讨论了保守假基因作为VH区段储备库的可能性。
