Schematic representation of the mRNA export pathway in yeast (see for a full description). mRNAs associate with protein factors into messenger RNPs (mRNPs) which are then exported through the NPC by the TAP/p15 heterodimer (Mex67/Mtr2 in yeast), that functions as a general mRNA export receptor. TAP/p15 operates in association with TREX (Transcription/Export), a complex that connects transcription with mRNA export and the THO complex. In yeast there is a an additional complex named TREX-2, that is also capable of mediating the nuclear export of mRNPs. Each box represents a human/yeast protein and the absence of human predicted orthologs, is represented by "X". Proteins are colored according to the stage in which they act and lines represent interactions between the complexes. TREX: transcription-coupled to export complex. Pol II: RNA Polymerase II.