ATP-binding RNA helicase component of the TREX complex involved in transcription elongation and required for the export of mRNA out of the nucleus. SUB2 also plays a role in pre-mRNA splicing and spliceosome assembly. May be involved in rDNA and telomeric silencing, and maintenance of genome integrity. ATP + H2O = ADP + H(+) + phosphate Component of the TREX complex composed of at least SUB2, TEX1, YRA1 and the four THO complex components: HPR1, MFT1, THO2 and THP1. Interacts with HPR1, YRA1, and YRA2. SUB2 may mediate the interaction between the THO complex and YRA1. Associates with growing mRNP complexes during transcription. This association requires the presence of HPR1. Interacts also with SAC3. The Q motif is unique to and characteristic of the DEAD box family of RNA helicases and controls ATP binding and hydrolysis. Present with 51700 molecules/cell in log phase SD medium. Belongs to the DEAD box helicase family. DECD subfamily.