The THO/TREX complex is the transcription- and export-related complex associated with spliceosomes that preferentially deal with spliced mRNAs as opposed to unspliced mRNAs. Thoc2 plays a role in RNA polymerase II (RNA pol II)-dependent transcription and is required for the stability of DNA repeats [1]. In humans, the TRE complex is comprised of the exon-junction-associated proteins Aly/REF and UAP56 together with the THO proteins THOC1 (hHpr1/p84), Thoc2 (hRlr1), THOC3 (hTex1), THOC5 (fSAP79), THOC6 (fSAP35), and THOC7 (fSAP24). Although much evidence indicates that the function of the TREX complex as an adaptor between the mRNA and components of the export machinery is conserved among eukaryotes, in Drosophila the majority of mRNAs can be exported from the nucleus independently of the THO complex [2].

1: A novel yeast gene, THO2, is involved in RNA pol II transcription and provides new evidence for transcriptional elongation-associated recombination. Piruat JI, Aguilera A; EMBO J. 1998;17:4859-4872. PMID:9707445

2: Protein composition of human mRNPs spliced in vitro and differential requirements for mRNP protein recruitment. Merz C, Urlaub H, Will CL, Luhrmann R; RNA. 2007;13:116-128. PMID:17095540