van der Maarel S, van Dijk K W, Alexander C M, Sasso E H, Bull A, Milner E C
Virginia Mason Research Center, Seattle, WA 98101.
J Immunol. 1993 Apr 1;150(7):2858-68.
To investigate the organization and evolution of VH gene segments, we characterized the elements belonging to the VH4 gene family from the germline of a single subject. One hundred sixty VH4-carrying lambda-phage clones were isolated from a genomic library. A combination of hybridization and sequence analysis yielded 13 distinct VH4 clones. Six of these elements had one or more nucleotide substitutions that distinguished them from previously identified VH4 genes, whereas seven elements were identical to previously described VH4 genes. In four of the six new sequences, nucleotide substitutions resulted in amino acid replacements. One pseudogene was identified. On the basis of sequence-specific hybridization using oligonucleotide probes corresponding to these sequences, each of the elements could be assigned to a specific band in a BglII digest. Since the VH4-carrying BglII bands have been mapped in genomic DNA, it was also possible to assign chromosomal locations to the specific VH4 elements. The results indicate that the majority of VH4 elements are located in a region of approximately 500 kb, extending from approximately 500 to 1000 kb 5' of the JH locus. The distribution of shared structural motifs among the VH4 elements indicates that the VH4 gene family has evolved through repeated duplication and gene conversion events.
为了研究VH基因片段的组织和进化，我们对来自单个个体种系的属于VH4基因家族的元件进行了表征。从基因组文库中分离出160个携带VH4的λ噬菌体克隆。杂交和序列分析相结合产生了13个不同的VH4克隆。其中六个元件有一个或多个核苷酸取代，这使它们与先前鉴定的VH4基因有所区别，而七个元件与先前描述的VH4基因相同。在六个新序列中的四个中，核苷酸取代导致了氨基酸替换。鉴定出一个假基因。基于使用与这些序列相对应的寡核苷酸探针进行的序列特异性杂交，每个元件都可以在BglII消化物中被分配到一个特定的条带。由于携带VH4的BglII条带已在基因组DNA中定位，因此也有可能将特定的VH4元件分配到染色体位置。结果表明，大多数VH4元件位于大约500 kb的区域内，从JH基因座5'端大约500至1000 kb处延伸。VH4元件之间共享结构基序的分布表明，VH4基因家族是通过重复复制和基因转换事件进化而来的。
