DSIF factor Spt5 coordinates transcription, maturation and exoribonucleolysis of RNA polymerase II transcripts

The timely termination of RNA polymerase II (Pol II) transcription is essential for recycling of this enzyme and preventing transcriptional interference. While 5'-3' exonuclease Xrn2 is known to degrade nascent RNA after poly(A) site cleavage to promote Pol II release, its molecular mechanism remains not fully understood. Spt5 is one of highly conserved transcription factors that controls and regulates multiple aspects of Pol II transcription. Here, using mass spectrometry analysis of immunoprecipitated Flag-tagged Spt5-WT and Spt5-mutant complexes from fission yeast cells, we show that Xrn2 is highly enriched in these samples. Through in vitro BS3 crosslinking experiments with purified components, we further demonstrated that Xrn2 associates with transcription machinery and we probed interfaces between different subunits of transcription machinery