SPT5 stabilizes RNA polymerase II, orchestrates transcription cycles, and maintains the enhancer landscape

Transcription progression is governed by multitasking regulators including SPT5, an evolutionarily conserved factor implicated in virtually all transcriptional steps from enhancer activation to termination. Here we utilize a rapid degradation system and reveal crucial functions of SPT5 in maintaining cellular and chromatin RNA polymerase II (Pol II) levels. Rapid SPT5 depletion causes a pronounced reduction of paused Pol II at promoters and enhancers, distinct from NELF degradation resulting in short-distance paused Pol II redistribution. Most genes exhibit downregulation but not upregulation, accompanied by greatly impaired transcription activation, altered chromatin landscape at enhancers, and severe Pol II processivity defects at gene bodies. Phosphorylation of an SPT5 linker at serine 666 potentiates pause release and is antagonized by Integrator-PP2A (INTAC) targeting SPT5 and Pol II, while phosphorylation of SPT5 C-terminal region links to 3' end termination. Our findings position SPT5 as an essential positive regulator of global transcription.

转录进程由包括SPT5在内的多任务调控因子所调控，SPT5是一种进化保守的因子，参与从增强子激活到转录终止的几乎所有转录步骤。本研究利用快速降解系统，揭示了SPT5在维持细胞内及染色质上RNA聚合酶II（Pol II）水平中的关键功能。SPT5的快速耗竭会导致启动子和增强子处的暂停态Pol II显著减少，这与NELF降解引发的短距离暂停态Pol II重分布现象截然不同。多数基因呈现表达下调而非上调，同时伴随转录激活严重受损、增强子处染色质景观改变，以及基因体处Pol II延伸持续性的严重缺陷。SPT5连接区丝氨酸666的磷酸化可促进暂停释放，而靶向SPT5与Pol II的整合子-PP2A复合物（INTAC）会拮抗该磷酸化过程；此外，SPT5 C端区域的磷酸化与3'端终止相关。本研究的发现将SPT5定位为全局转录的必需正向调控因子。