Assembly of functional ALT-associated promyelocytic leukemia bodies requires Nijmegen Breakage Syndrome 1.
Assembly of functional ALT-associated promyelocytic leukemia bodies requires Nijmegen Breakage Syndrome 1.
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发表时间：
2003-05
期刊：
影响因子：
11.2
通讯作者：
Guikai Wu;Xianzhi Jiang;Wen-Hwa Lee;Phang-lang Chen
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作者：
Guikai Wu;Xianzhi Jiang;Wen-Hwa Lee;Phang-lang Chen
永生化细胞通过端粒酶依赖性过程或端粒酶独立途径（称为端粒替代延长（ALT））来维持端粒长度。同源重组与酵母和人类 ALT 细胞的 ALT 通路有关。在 ALT 细胞中，两种类型的 DNA 双链断裂修复和同源重组因子（Rad50/Mre11/NBS1 复合物和 Rad51/Rad52）以及复制因子 (RPA) 和端粒结合蛋白（TRF1 和 TRF2）与 ALT 相关 PML 小体 (APB) 相关。 S-G(2) 晚期的 DNA 合成与 APB 相关，APB 含有端粒 DNA，因此是维持端粒长度的潜在位点。在这里，我们发现乳腺癌易感基因产物乳腺癌易感基因 1 和酵母 Rap1 的人类同源物 hRap1 也与 APB 相关，特别是在细胞周期的晚期 S-G(2) 阶段。我们还表明，双链断裂修复因子与 APB 的定位不同于它们与电离辐射诱导的核焦点的关联。为了系统地探讨 APB 组装所涉及的机制，我们分别研究了奈梅亨断裂综合征 1 (NBS1) 和 TRF1 在此过程中的作用。我们证明NBS1在Rad50、Mre11和乳腺癌易感基因1（但不是Rad51或TRF1）向APB的组装和/或招募中发挥关键作用。 NBS1 的 NH(2) 末端，特别是 BRCA1 COOH 末端结构域，是该活性所必需的。尽管TRF1直接与NBS1相互作用，但Rad50/Mre11/NBS1或Rad51与APB的关联是可有可无的。 NBS1/Mre11 和 APB 之间相互作用的扰动与 APB 相关的 BrdUrd 掺入减少相关，这与这些位点 DNA 合成减少一致。总而言之，这些结果支持了一个模型，其中 NBS1 在 APB 的组装中发挥着至关重要的作用，而 APB 的功能是维持人类 ALT 细胞中的端粒。
Immortalized cells maintain telomere length through either a telomerase-dependent process or a telomerase-independent pathway termed alternative lengthening of telomeres (ALT). Homologous recombination is implicated in the ALT pathway in both yeast and human ALT cells. In ALT cells, two types of DNA double-strand break repair and homologous recombination factors, the Rad50/Mre11/NBS1 complex and Rad51/Rad52 along with replication factors (RPA) and telomere binding proteins (TRF1 and TRF2), are associated with the ALT-associated PML body (APB). DNA synthesis in late S-G(2) is associated with APBs, which contain telomeric DNA and, are therefore, potential sites for telomere length maintenance. Here, we show that the breast cancer susceptibility gene product, breast cancer susceptibility gene 1, and the human homologue of yeast Rap1, hRap1, are also associated with APBs specifically during late S-G(2) phase of the cell cycle. We additionally show that the localization of the double-strand break repair factors with APBs is distinct from their association with ionizing radiation-induced nuclear foci. To systematically explore the mechanism involved in the assembly of APBs, we examine the role of Nijmegen breakage syndrome 1 (NBS1) and TRF1 in this process, respectively. We demonstrated that NBS1 plays a key role in the assembly and/or recruitment of Rad50, Mre11, and breast cancer susceptibility gene 1, but not Rad51 or TRF1, to APBs. The NH(2) terminus of NBS1, specifically the BRCA1 COOH-terminal domain, is required for this activity. Although TRF1 interacts with NBS1 directly, it is dispensable for the association of either Rad50/Mre11/NBS1 or Rad51 with APBs. Perturbation of the interactions between NBS1/Mre11 and APBs correlates with reduced BrdUrd incorporation associated with APBs, consistent with decreased DNA synthesis at these sites. Taken together, these results support a model in which NBS1 has a vital role in the assembly of APBs, which function to maintain telomeres in human ALT cells.