B) Deletion of the N-terminal domain of Sen1 provokes dramatic defects in transcription termination in vivo. Northern blot analyses of three well-characterized NNS-targets, the CUT NEL025c and the snoRNAs SNR13 and SNR33, in a Sen1-AID (auxin-induced degron) strain carrying an empty vector or a plasmid expressing either the wt or the indicated versions of SEN1. Sen1-AID was depleted for 2h by the addition of 500 μM indole-3-acetic acid (IAA) to monitor the capacity of the plasmid-borne versions of SEN1 to induce transcription termination. The expected RNA species resulting from inefficient termination (RT for readthrough species) are indicated. assays were performed in a ∆rrp6 background to detect the primary products of NNS-dependent termination and the U4 RNA is used as a loading control. 