Molecular Cell, 26 February, 2025, DOI：https://doi.org/10.1016/j.molcel.2025.01.023

Pcf11/Spt5 condensates stall RNA polymerase II to facilitate termination and piRNA-guided heterochromatin formation

Weiwei Liu, Lijun Deng, Ming Wang, Xiaojun Liu, Xuan Ouyang, Yuan Wang, Na Miao, Xiu Luo, Xueming Wu, Xiaohua Lu, Xiangjin Xv, Tianyu Zhang, Yu Li, Jinyao Ji, Zhenghao Qiao, Sheng Wang, Li Guan, Dong Li, Yunkun Dang, Chao Liu, Wei Li, Yadi Zhang, Zhenning Wang, Fei Xavier Chen, Chunlai Chen, Chengqi Lin, Wee Siong Sho Goh, Wenhao Zhou, Zhuojuan Luo, Pu Gao, Pilong Li, Yang Yu

Abstract

The PIWI-interacting RNA (piRNA) pathway plays a crucial role in protecting animal germ cells by repressing transposons. However, the mechanism of piRNA-guided heterochromatin formation and its relationship to transcriptional termination remains elusive. Through RNA interference screening, we discovered Pcf11 and PNUTS as essential for piRNA-guided silencing in Drosophila germ line. Enforced tethering of Pcf11 leads to co-transcriptional repression and RNA polymerase II (RNA Pol II) stalling, and both are dependent on an α-helical region of Pcf11 capable of forming condensates. An intrinsically disordered region can substitute for the α-helical region of Pcf11 in its silencing capacity and support animal development, arguing for a causal relationship between phase separation and Pcf11’s function. Pcf11 stalls RNA Pol II by preferentially forming condensates with the unphosphorylated Spt5, promoted by the PP1/PNUTS phosphatase during termination. We propose that Pcf11/Spt5 condensates control termination by decelerating polymerase elongation, a property exploited by piRNAs to silence transposons and initiate RNA-mediated heterochromatin formation.

Article link：https://www.sciencedirect.com/science/article/pii/S1097276525000577?via%3Dihub