ATP-dependent 5'->3' DNA/RNA helicase required for the expression and maturation of diverse classes of non-protein-coding RNAs like precursor tRNAs, rRNAs and small nuclear (snRNA) and nucleolar (snoRNA) RNAs. Directs RNA polymerase II transcription termination on snoRNAs as well as on several short protein-coding genes. May also play a role in transcription-coupled nucleotide excision repair. Interacts with RAD2, RNT1 and RPB1. Binds to multiple snoRNAs. Present with 125 molecules/cell in log phase SD medium. Belongs to the DNA2/NAM7 helicase family.