Figure 7. Influence of the transcription elongation rate on the requirement of Sen1 Nter for non‐coding transcription termination.

• A
  Decreasing the elongation rate alleviates the termination defects associated with deletion of Sen1 Nter. Northern blot assays performed in a Sen1‐AID, ∆rrp6 strain carrying a plasmid expressing the indicated versions of SEN1 upon depletion of the endogenous Sen1 protein as in former experiments. Where indicated, cells were treated with 50 mg/l of 6‐azauracil (6AU) for 2 h. Representative gel of one out of two independent biological replicates. The U4 RNA is used as a loading control. Probes used for RNA detection are described in Appendix Table S6.
• B
  Model for the role of the N‐terminal domain and the NIM in the control of Sen1 action at ncRNAs. Nrd1 and Sen1 are likely independently recruited to the elongation complex. The recruitment of Nrd1 and Nab3 is mediated by the recognition of specific RNA sequences and enhanced by the interaction of Nrd1 CID with the S5P‐CTD via the CID. Sen1 would be recruited either by unspecific binding to the nascent RNA or by possibly transient protein–protein interactions with RNAPII. The interaction of Sen1 NIM with Nrd1 CID also enhances Sen1 recruitment. The interaction of Sen1 Nter with the CTD could facilitate the loading of Sen1 to the nascent RNA in the vicinity of paused RNAPII. Sen1 would translocate along the nascent RNA to induce dissociation of the elongation complex. The release of Sen1 from Nrd1 would be required for the CID to be available to recruit TRAMP for subsequent processing/degradation of the released RNA.