Pax5 induces V-to-DJ rearrangements and locus contraction of the immunoglobulin heavy-chain gene
Pax5 induces V-to-DJ rearrangements and locus contraction of the immunoglobulin heavy-chain gene
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DOI：
10.1101/gad.291504
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发表时间：
2004-02-15
影响因子：
10.5
通讯作者：
Busslinger, M
中科院分区：
文献类型：
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作者：
Fuxa, M;Skok, J;Busslinger, M
(T)免疫球蛋白重链(IgH)基因的亚核位置和染色质状态与V(D)J重组的控制有关。此外，V(H)基因远端的V(H)到DJ(H)重排，而不是近端的V(H)基因重排，依赖于B系承诺因子Pax5(BSAP)。在这里，我们证明了来自Ikaros启动子的异位Pax5表达诱导了Ik(Pax5/+)胸腺细胞近端而不是远端的V(H)-DJ(H)重排，从而概括了Pax5(-/-)Pro-B细胞的功能丧失表型。这两种细胞类型的表型相似之处包括：(1)在没有V(H)-DJ(H)重排的情况下，V基因远端的染色质可及性；(2)B细胞特异性调节因子EBF的表达；(3)IgH等位基因在细胞核内的中心位置；(4)V(H)基因远端与延伸的IgH基因座近端片段的物理分离。Pax(5-/-)Pro-B细胞中Pax5表达的重建导致了IgH基因位点的大规模收缩和V(H)-DJ(H)远端重排。因此，在早期B淋巴细胞生成过程中，V(H)-DJ(H)重组受到两步调控。IgH位点首先从其在核外围的默认位置向核中心重新定位，这促进了近端V(H)-DJ(H)的重组。Pax5随后在一种未知因子的协同作用下激活了位点收缩和V(H)-DJ(H)远端重排，该因子存在于前B细胞中，但在胸腺细胞中不存在。
(T)he subnuclear location and chromatin state of the immunoglobulin heavy chain (IgH) locus have been implicated in the control of V(D)J recombination. V(H)-to-DJ(H) rearrangement of distal, but not proximal V(H) genes, furthermore, depends on the B-lineage commitment factor Pax5 (BSAP). Here we demonstrate that ectopic Pax5 expression from the Ikaros promoter induces proximal rather than distal V(H)-DJ(H) rearrangements in Ik(Pax5/+) thymocytes, thus recapitulating the loss-of-function phenotype of Pax5(-/-) pro-B cells. The phenotypic similarities of both cell types include (1) chromatin accessibility of distal V. genes in the absence of V(H)-DJ(H) rearrangements, (2) expression of the B-cell-specific regulator EBF, (3) central location of IgH alleles within the nucleus, and (4) physical separation of distal V(H) genes from proximal segments in an extended IgH locus. Reconstitution of Pax5 expression in Pax(5-/-) pro-B cells induced large-scale contraction and distal V(H)-DJ(H) rearrangements of the IgH locus. Hence, V(H)-DJ(H) recombination is regulated in two steps during early B-lymphopoiesis. The IgH locus is first repositioned from its default location at the nuclear periphery toward the center of the nucleus, which facilitates proximal V(H)-DJ(H) recombination. Pax5 subsequently activates locus contraction and distal V(H)-DJ(H) rearrangements in collaboration with an unknown factor that is present in pro-B cells, but absent in thymocytes.