The  telomeric Cdc13-Stn1-Ten1 complex regulates RNA pol II transcription

Specialized telomeric proteins have an essential role in maintaining genome stability through chromosome end protection and telomere length regulation. In the yeast Saccharomyces cerevisiae, the evolutionary conserved CST complex, composed of the Cdc13, Stn1 and Ten1 proteins, largely contributes to these functions. Here, we report the existence of genetic interactions between TEN1 and several genes coding for transcription regulators. Molecular assays confirmed this novel function of Ten1 and further established that it regulates the occupancies of RNA polymerase II and the Spt5 elongation factor within transcribed genes. Since Ten1, but also Cdc13 and Stn1, were found to physically associate with Spt5, we propose that Spt5 represents the target of CST in transcription regulation. Moreover, CST physically associated with Hmo1, previously shown to mediate the architecture of S phase-transcribed genes. The fact that, genome-wide, the promoters of genes down-regulated in the ten1-31 mutant are prefentially bound by Hmo1, leads us to propose a potential role for CST in synchronizing transcription with replication fork progression following head-on collisions. The present finding of the existence of extra-telomeric functions for Ten1 in the regulation of RNA polymerase II in cooperation with Stn1 and Cdc13 has profound repercussions on future studies both on telomeric and transcription pathways. Overall design: 6 RNA-seq samples: 2 conditions with 3 replicates each; 12 ChIP-seq samples: 4 IPs and 2 Inputs, with 2 repliactes each.

特化端粒蛋白通过保护染色体末端、调控端粒长度，在维持基因组稳定性中发挥核心作用。在酿酒酵母（Saccharomyces cerevisiae）中，由Cdc13、Stn1和Ten1蛋白组成的进化保守CST复合物（CST complex）在很大程度上介导了上述功能。本研究报道了TEN1与多个编码转录调控因子的基因之间存在遗传互作。分子实验验证了Ten1的这一全新功能，并进一步证实其可调控转录基因内RNA聚合酶II（RNA polymerase II）与转录延伸因子Spt5的结合占有率。鉴于Ten1、Cdc13与Stn1均被发现可与Spt5发生物理结合，本研究提出Spt5是CST复合物在转录调控中的作用靶点。此外，CST复合物可与Hmo1发生物理结合，而此前已有研究表明Hmo1可介导S期转录基因的染色质构象。全基因组分析显示，ten1-31突变体中下调基因的启动子区域优先被Hmo1结合，基于此我们提出CST复合物可能在转录与复制叉正面碰撞后的进程同步中发挥作用。本研究发现Ten1可与Stn1、Cdc13协同调控RNA聚合酶II，且该功能属于端粒外功能，这一发现对端粒生物学与转录通路相关的后续研究均具有深远影响。实验设计概述：共6个RNA测序（RNA-seq）样本，分为2组实验条件，每组设置3次生物学重复；共12个染色质免疫共沉淀测序（ChIP-seq）样本，包含4种免疫沉淀（IP）样本与2个输入对照样本，每组均设置2次生物学重复。