Alternative Lengthening of Telomeres is a Self-Perpetuating Process in ALT-Associated PML Bodies

This data include the original images of western blots and microscopy for the paper titled "Alternative Lengthening of Telomeres is a Self-Perpetuating Process in ALT-Associated PML Bodies"

Alternative lengthening of telomeres (ALT) is mediated by break-induced replication (BIR), but how BIR is regulated at telomeres is poorly understood. Here, we show that telomeric BIR is a self-perpetuating process. By tethering PML-IV to telomeres, we induced telomere clustering in ALT-associated PML bodies (APBs) and a POLD3-dependent ATR response at telomeres, showing that BIR generates replication stress. Ablation of BLM helicase activity in APBs abolishes telomere synthesis but causes multiple chromosome bridges between telomeres, revealing a function of BLM in processing inter-telomere BIR intermediates. Interestingly, the accumulation of BLM in APBs requires its own helicase activity and POLD3, suggesting that BIR triggers a feedforward loop to further recruit BLM. Enhancing BIR induces PIAS4-mediated TRF2 SUMOylation, and PIAS4 loss deprives APBs of repair proteins and compromises ALT telomere synthesis. Thus, a BLM-driven and PIAS4-mediated feedforward loop operates in APBs to perpetuate BIR, providing a critical mechanism to extend ALT telomeres.

本数据集收录了论文《端粒的替代延长是ALT相关PML体中自我维持的过程》中所述的Western Blot和显微镜图像。端粒的替代延长（ALT）由断裂诱导的复制（BIR）介导，但BIR在端粒中的调控机制尚不明确。在本研究中，我们揭示了端粒BIR是一种自我维持的过程。通过将PML-IV锚定于端粒，我们诱导了ALT相关PML体（APBs）中端粒的聚集，并观察到端粒处的POLD3依赖性的ATR反应，表明BIR产生了复制压力。在APBs中消除BLM解旋酶活性消除了端粒的合成，但导致端粒间形成多个染色体桥，揭示了BLM在处理端粒间BIR中间体中的功能。有趣的是，BLM在APBs中的积累需要其自身的解旋酶活性和POLD3，这表明BIR触发了正向反馈循环以进一步招募BLM。增强BIR诱导了PIAS4介导的TRF2 SUMO化，而PIAS4的丢失剥夺了APBs的修复蛋白，并损害了ALT端粒的合成。因此，一个由BLM驱动并由PIAS4介导的正向反馈循环在APBs中运作，以维持BIR，提供了延长ALT端粒的关键机制。