Trans-chromosomal recombination within the Ig heavy chain switch region in B lymphocytes
Trans-chromosomal recombination within the Ig heavy chain switch region in B lymphocytes
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DOI：
10.1073/pnas.95.20.11840
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发表时间：
1998-09-29
影响因子：
11.1
通讯作者：
Knight, KL
中科院分区：
文献类型：
--
作者：
Kingzette, M;Spieker-Polet, H;Knight, KL
B淋巴细胞中的体细胞DNA重排，包括V（D）J基因重排和同种型转换，通常以顺式发生，即，然而，在染色体内，我们先前表明，3 - 7%的伊加重链具有反式编码的VH和C α区。为了确定V-H和C α的反式缔合是否通过反式染色体重组、反式剪接或反式染色体基因转换发生，我们产生并分析了8个具有反式缔合的V-H和C α重链的IgA分泌兔杂交瘤。通过ELISA和核苷酸序列分析，我们发现VH和C α区是由生殖系中反式的基因编码的。我们从一个杂交瘤的fosmid文库中克隆了重排的VDJ-C α基因，发现表达的VH和C α基因是并列的。此外，并置的VH和CLY基因来源于不同的IgH等位基因。从同一杂交瘤中，我们还鉴定了一个具有另一个预期的跨染色体重组产物的fosmid克隆。重组断裂点发生在S mu/S α区域内，表明在同种型转换期间通过跨染色体重组发生了V-H和C α基因的转关联。我们的结论是，在正常动物的B淋巴细胞的IgH基因座内，转染色体重组发生在一个出乎意料的高频率（7%），这可能解释了高发病率的B细胞肿瘤所产生的癌基因易位到IgH基因座。
Somatic DNA rearrangements in B lymphocytes, including V(D)J gene rearrangements and isotype switching, generally occur in cis, i.e., intrachromosomally, We showed previously, however, that 3 to 7% of IgA heavy chains have the VH and C alpha regions encoded in trans. To determine whether the trans-association of V-H and C alpha occurred by trans-chromosomal recombination, by trans-splicing, or by trans-chromosomal gene conversion, we generated and analyzed eight IgA-secreting rabbit hybridomas with trans associated V-H and C alpha heavy chains. By ELISA and by nucleotide sequence analysis we found that the VH and C alpha regions were encoded by genes that were in trans in the germline, We cloned the rearranged VDJ-C alpha gene from a fosmid library of one hybridoma and found that the expressed VH and C alpha genes were juxtaposed. Moreover, the juxtaposed VH and CLY genes originated from different IgH alleles, From the same hybridoma, we also identified a fosmid clone with the other expected product of a trans-chromosomal recombination. The recombination breakpoint occurred within the S mu/S alpha region, indicating that the trans-association of V-H and C alpha genes occurred by trans chromosomal recombination during isotype switching. We conclude that trans-chromosomal recombination occurs at an unexpectedly high frequency (7%) within the IgH locus of B lymphocytes in normal animals, which may explain the high incidence of B-cell tumors that arise from oncogene translocation into the IgH locus.