Diotti Raffaella, Kalan Sampada, Matveyenko Anastasiya, Loayza Diego
Department of Biological Sciences, Hunter College and CUNY Graduate Center, New York, New York.
Mol Cancer Res. 2015 Mar;13(3):402-10. doi: 10.1158/1541-7786.MCR-14-0381. Epub 2014 Dec 17.
Telomeres consist of TTAGGG repeats bound by the shelterin complex and end with a 3' overhang. In humans, telomeres shorten at each cell division, unless telomerase (TERT) is expressed and able to add telomeric repeats. For effective telomere maintenance, the DNA strand complementary to that made by telomerase must be synthesized. Recent studies have discovered a link between different activities necessary to process telomeres in the S phase of the cell cycle to reform a proper overhang. Notably, the human CST complex (CTC1/STN1/TEN1), known to interact functionally with the polymerase complex (POLA/primase), was shown to be important for telomere processing. Here, focus was paid to the catalytic (POLA1/p180) and accessory (POLA2/p68) subunits of the polymerase, and their mechanistic roles at telomeres. We were able to detect p68 and p180 at telomeres in S-phase using chromatin immunoprecipitation. We could also show that the CST, shelterin, and polymerase complexes interact, revealing contacts occurring at telomeres. We found that the polymerase complex could associate with telomerase activity. Finally, depletion of p180 by siRNA led to increased overhang amounts at telomeres. These data support a model in which the polymerase complex is important for proper telomeric overhang processing through fill-in synthesis, during S phase. These results shed light on important events necessary for efficient telomere maintenance and protection.
This study describes the interplay between DNA replication components with proteins that associate with chromosome ends, and telomerase. These interactions are proposed to be important for the processing and protection of chromosome ends.
端粒由与端粒保护蛋白复合体结合的TTAGGG重复序列组成，末端为3'端悬突。在人类中，除非端粒酶（TERT）表达并能够添加端粒重复序列，否则端粒会在每次细胞分裂时缩短。为了有效地维持端粒，必须合成与端粒酶合成的DNA链互补的DNA链。最近的研究发现，在细胞周期的S期处理端粒以重新形成合适的端悬突所需的不同活性之间存在联系。值得注意的是，已知在功能上与聚合酶复合体（POLA/引发酶）相互作用的人类CST复合体（CTC1/STN1/TEN1），对端粒处理很重要。在这里，重点关注聚合酶的催化亚基（POLA1/p180）和辅助亚基（POLA2/p68）及其在端粒处的作用机制。我们能够使用染色质免疫沉淀法在S期的端粒处检测到p68和p180。我们还可以表明，CST、端粒保护蛋白和聚合酶复合体相互作用，揭示了在端粒处发生的相互作用。我们发现聚合酶复合体可能与端粒酶活性相关。最后，通过小干扰RNA（siRNA）耗尽p180会导致端粒处的端悬突量增加。这些数据支持了一个模型，即聚合酶复合体在S期通过填补合成对正确的端粒端悬突处理很重要。这些结果揭示了有效维持和保护端粒所需的重要事件。
本研究描述了DNA复制成分与与染色体末端相关的蛋白质以及端粒酶之间的相互作用。这些相互作用被认为对染色体末端的处理和保护很重要。
