Telomerase function and binding at endogenous G-rich regions (ChIP)

Telomerase majorly functions at telomeres but under adverse conditions acts at endogenous regions, which is often observed in cancer calls. By mapping the global occupancy of the catalytic subunit of telomerase (Est2), we reveal that telomerase binds to multiple genomic loci, which we termed ‘non-telomere-binding sites’ (NTBS). We characterized under when and why Est2 binds to such sites and could show that telomerase is inactive but becomes activated upon global DNA damage. Indicating that those regions are of particular risk for genome stability. Using biochemical and molecular experiments we further characterized Est2 binding to NTBS. In contrast to Est2 binding to telomere neither Cdc13 nor Ku70/80 is crucial for the binding to NTBS. Strikingly, using Hi-C, we demonstrate that chromatin organization is essential and drives the interaction of Est2-NTBS binding. The here presented results provide a novel model of telomerase regulation using endogenous regions as “parking spots” awaiting its canonical function at telomeres.端粒酶（telomerase）的核心功能位点为端粒（telomeres），但在不良应激条件下，其可靶向结合内源性基因组区域，该现象在癌细胞中屡被观测到。我们通过绘制端粒酶催化亚基Est2的全基因组结合占据图谱，发现端粒酶可结合多个基因组位点，我们将其命名为“非端粒结合位点（non-telomere-binding sites，NTBS）”。我们系统表征了Est2结合此类位点的时机与分子机制，证实此时端粒酶处于失活状态，仅在全基因组DNA损伤发生时才会被激活，这表明这些区域对基因组稳定性存在显著威胁。我们进一步通过生化与分子生物学实验，对Est2结合NTBS的过程进行了深入解析。与Est2结合端粒的过程不同，Cdc13以及Ku70/80复合物均非Est2结合NTBS所必需的调控因子。尤为关键的是，借助Hi-C实验，我们证明染色质三维组织是Est2与NTBS结合的必要条件，并直接驱动了二者的相互作用。本研究结果提出了一种全新的端粒酶调控模型：内源性区域可作为“停靠位点”，等待端粒酶发挥其在端粒处的经典功能。