Probing PML body function in ALT cells reveals spatiotemporal requirements for telomere recombination
Probing PML body function in ALT cells reveals spatiotemporal requirements for telomere recombination
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DOI：
10.1073/pnas.0907689106
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发表时间：
2009-09-15
影响因子：
11.1
通讯作者：
Londono-Vallejo, Arturo
中科院分区：
文献类型：
--
作者：
Draskovic, Irena;Arnoult, Nausica;Londono-Vallejo, Arturo
早幼粒细胞白血病（PML）小体（也称为ND 10）是涉及多种细胞过程的动态核结构。ALT相关PML小体（APB）是专门在端粒酶阴性肿瘤中发现的PML小体，其中端粒通过基于重组的替代（ALT）机制维持。虽然已经表明APB直接参与ALT细胞的端粒代谢，但其确切的作用和结构仍然难以捉摸。在这里，我们发现ALT细胞中的PML小体与染色体末端形成小的、空间上明确的簇，平均包含2-5个端粒。使用一种创新的方法，轻轻地扩大PML机构在活细胞中，同时保留其整体组织，我们表明，这种物理放大的APBs在空间上解决了集群中的单个端粒，但不干扰的潜力的APB招募染色体末端。我们发现，在PML机构的端粒聚类是细胞周期调节和一个集群内的独特的端粒与重组蛋白。APBs的抑制诱导了端粒-端粒重组中间体的积累，这些中间体在中期扩散和连接异源染色体上可见。这些重组中间体的链组成表明，这种重组被限制在一个狭窄的时间窗口，在细胞周期复制后。这些数据提供了强有力的证据，即PML体不仅是ALT细胞的标记，而且通过将染色体末端聚集在一起和通过促进异源染色体之间的端粒-端粒相互作用在端粒重组中发挥直接作用。
Promyelocytic leukemia (PML) bodies ( also called ND10) are dynamic nuclear structures implicated in a wide variety of cellular processes. ALT-associated PML bodies (APBs) are specialized PML bodies found exclusively in telomerase-negative tumors in which telomeres are maintained by recombination-based alternative (ALT) mechanisms. Although it has been suggested that APBs are directly implicated in telomere metabolism of ALT cells, their precise role and structure have remained elusive. Here we show that PML bodies in ALT cells associate with chromosome ends forming small, spatially well-defined clusters, containing on average 2-5 telomeres. Using an innovative approach that gently enlarges PML bodies in living cells while retaining their overall organization, we show that this physical enlargement of APBs spatially resolves the single telomeres in the cluster, but does not perturb the potential of the APB to recruit chromosome extremities. We show that telomere clustering in PML bodies is cell-cycle regulated and that unique telomeres within a cluster associate with recombination proteins. Enlargement of APBs induced the accumulation of telomere-telomere recombination intermediates visible on metaphase spreads and connecting heterologous chromosomes. The strand composition of these recombination intermediates indicated that this recombination is constrained to a narrow time window in the cell cycle following replication. These data provide strong evidence that PML bodies are not only a marker for ALT cells but play a direct role in telomere recombination, both by bringing together chromosome ends and by promoting telomere-telomere interactions between heterologous chromosomes.