The THO complex functions in mRNP biogenesis at the interface between transcription and export of mRNA from the nucleus. Proteins are shown with their yeast name followed by the name of the human homolog, where the two differ, for Nab2, Mtr2/p15, Sub2/UAP56, Mex67/TAP, Yra1/ALY, or with the yeast name followed by the Drosophila name for Sus1/ENY2. Protein complexes are shown in capital letters: THO, THSC (also called TREX-2) and SAGA. Proteins that interact with each other or between which a physical connection has been reported are in the same color. Sus1 can act as a subunit of both THSC and SAGA complexes. Unlabeled proteins in gray represent other factors important for mRNP biogenesis and export. NPC, nuclear pore complex; RNAPII, RNA polymerase II.