Cotranscriptional RNA cleavage by Drosha homolog Pac1 triggers transcription termination in fission yeast. [ChIP-Seq]

RNAse III is an evolutionarily conserved family of endoribonuclease that cleaves dsRNA structures. Here we studied RNAse III homolog Pac1 In fission yeast to shed light on underappreciated roles of Drosha. We found that Pac1 co-transcriptional cleavage of nascent hairpin RNA structures trigger transcriptional termination by creating an entry point for “torpedo” exonucleases – that is, exonuclease that degrade the nascent RNA until they bump into the transcribing polymerases. As such termination pathway decouple termination from pre-mRNA polyadenylation, the nascent transcript are destabilized upon Pac1 cleavage, therefore expending the paradigm of post-transcriptional regulation of gene expression. Overall design: ChIP assays of Pac1-TAP in wild-type and of of Pol II occupancy (8WG16 antibody) in wild-type and Pac1-Anchor-Away strain.