Telomere maintenance by telomerase is essential for continuous proliferation of human cells and is vital for the survival of stem cells and 90% of cancer cells. To compensate for telomeric DNA lost during DNA replication, telomerase processively adds GGTTAG repeats to chromosome ends by copying the template region within its RNA subunit. Between repeat additions, the RNA template must be recycled. How telomerase remains associated with substrate DNA during this critical translocation step remains unknown. Using a single-molecule telomerase activity assay utilizing high-resolution optical tweezers, we demonstrate that stable substrate DNA binding at an anchor site within telomerase facilitates the processive synthesis of telomeric repeats. The product DNA synthesized by telomerase can be recaptured by the anchor site or fold into G-quadruplex structures. Our results provide detailed mechanistic insights into telomerase catalysis, a process of critical importance in aging and cancer.

端粒酶对端粒的维持对于人类细胞的持续增殖至关重要，对干细胞和 90% 的癌细胞的存活至关重要。为了补偿在 DNA 复制过程中丢失的端粒 DNA，端粒酶通过复制其 RNA 亚基内的模板区域，将 GGTTAG 重复序列不断地添加到染色体末端。在重复添加之间，必须回收 RNA 模板。在这个关键的易位步骤中，端粒酶如何与底物 DNA 保持联系仍然未知。我们使用高分辨率光学镊子进行单分子端粒酶活性测定，证明在端粒酶内锚点处的稳定底物 DNA 结合有助于端粒重复序列的合成。端粒酶合成的产物DNA可以被锚定位点重新捕获或折叠成G-四链体结构。我们的研究结果为端粒酶催化提供了详细的机制见解，这是一个在衰老和癌症中至关重要的过程。