Restrictor synergizes with Symplekin and PNUTS to terminate extragenic transcription
Transcription termination pathways mitigate the detrimental consequences of unscheduled promiscuous initiation occurring at hundreds of thousands of genomic cis-regulatory elements, thus representing cornerstones of genomic regulation in eukaryotes. Restrictor, a complex conserved from worms to humans and composed of the RNA-binding protein ZC3H4 and of WDR82, a Pol II-carboxyterminal repeat domain (CTD)-interacting protein, is required to suppress long-range, processive transcription at thousands of extragenic sites, with instead comparatively limited effects on gene transcription. Restrictor contains no RNA cleavage subunit and does not coopt known cleavage complexes, indicating alternative termination mechanisms. Here we show that Restrictor-driven termination involves Symplekin, a protein associated with RNA cleavage complexes but also involved in cleavage-independent, phosphatase-dependent termination of non-coding RNAs in yeast. Competition among Restrictor, the cleavage and polyadenylation specificity complex (CPSF) and the histone cleavage complex for a limited pool of Symplekin resulted in mutual regulation, thus revealing unexpected regulatory interactions among multiple transcription termination pathways and a general role of Symplekin in both genic and extragenic cleavage-independent termination pathways. Overall design: Transcriptome analysis to measure transcription in HCT-116 cell depleted by ZC3H4, SYMPK  and SYMPK + ZC3H4. Genotipe = ZC3H4-mAID:dTAG-SYMPK. 2 Replicates.