InterPro domain: IPR008501

The THO complex (THOC) is involved in transcription elongation and mRNA export from the nucleus [ 1 ]. This entry represents the subunit THOC7, which is found in higher eukaryotes, and the non-homologous subunit Mft1 found in yeast.

Mft1 is a component the THO subcomplex of the TREX complex, which operates in coupling transcription elongation to mRNA export [ 2 ]. The THO complex is recruited to transcribed genes and moves along the gene with the elongating polymerase during transcription [ 3 ]. THO is important for stabilising nascent RNA in the RNA polymerase II elongation complex by preventing formation of DNA:RNA hybrids behind the elongating polymerase [ 4 ]. It functions in cotranscriptional formation of an export-competent messenger ribonucleoprotein particle (mRNP) by facilitating the loading of ATP-dependent RNA helicase Sub2 and the mRNA export factor Yra1 along the nascent mRNA [ 5 ].

In mammals, the THO complex specifically associates with spliced mRNA and not with unspliced pre-mRNA. It is recruited to spliced mRNAs by a transcription-independent mechanism. It binds to mRNA upstream of the exon-junction complex (EJC) and is recruited in a splicing- and cap-dependent manner to a region near the 5' end of the mRNA where it functions in mRNA export [ 6 , 7 ].

1. Genome-wide analysis of mRNAs regulated by the THO complex in Drosophila melanogaster. Nat. Struct. Mol. Biol. 11, 558-66
2. The yeast THO complex and mRNA export factors link RNA metabolism with transcription and genome instability. EMBO J. 21, 3526-35
3. Molecular evidence that the eukaryotic THO/TREX complex is required for efficient transcription elongation. J. Biol. Chem. 278, 39037-43
4. Cotranscriptionally formed DNA:RNA hybrids mediate transcription elongation impairment and transcription-associated recombination. Mol. Cell 12, 711-21
5. Biochemical analysis of TREX complex recruitment to intronless and intron-containing yeast genes. EMBO J. 23, 2620-31
6. Recruitment of the human TREX complex to mRNA during splicing. Genes Dev. 19, 1512-7
7. Human mRNA export machinery recruited to the 5' end of mRNA. Cell 127, 1389-400