Alternative titles; symbols
HGNC Approved Gene Symbol: THOC7
Cytogenetic location: 3p14.1 Genomic coordinates (GRCh38): 3:63,833,870-63,864,484 (from NCBI)
In yeast, the TREX (transcription/export) complex contains the THO transcription elongation complex, which functions in cotranscriptional recruitment of mRNA export proteins to the nascent transcript. The human TREX complex contains ALY (THOC4; 604171), UAP56 (DDX39B; 142560), and the human counterpart of the THO complex, which includes THOC7. The human TREX complex appears to be recruited to spliced mRNAs late in the splicing reaction rather than by direct cotranscriptional recruitment, as in yeast (Masuda et al., 2005).
By yeast 2-hybrid screening of a HeLa cell cDNA library using human NIF3L1 (605778) as bait, followed by database analysis, Tascou et al. (2003) cloned human THOC7, which they called NIF3L1BP1. The deduced 204-amino acid protein has a calculated molecular mass of 23.7 kD and contains a predicted leucine zipper domain. THOC7 shares 97% amino acid homology to the corresponding mouse sequence. Northern blot analysis of mouse tissues detected ubiquitous Thoc7 expression. Immunofluorescence studies localized THOC7 to the cytoplasm and nucleus; however, THOC7 colocalized with NIF3L1 in the cytoplasm only. Yeast 2-hybrid analysis with THOC7 deletion mutants showed that the C-terminal leucine zipper domain was required for binding to NIF3L1.
Using immunoprecipitation and mass spectrometric analysis of HeLa cell nuclear extracts, Masuda et al. (2005) found that the human TREX complex contained THO2 (THOC2; 300395), FSAP79 (THOC5; 612733), HPR1 (THOC1; 606930), UAP56, TEX1 (THOC3; 606929), FSAP35 (THOC6; 615403), ALY, and FSAP24 (THOC7). Immunodepletion and gel-filtration analyses revealed that THO2, HPR1, FSAP79, FSAP35, and FSAP24 were tightly associated in the THO complex, whereas UAP56, ALY, and TEX1 were more loosely associated. Immunoprecipitation of any TREX component efficiently immunoprecipitated spliced mRNA and cDNA transcripts, but not unspliced pre-mRNAs. Immunodepletion of any component had no effect on spliceosome assembly, splicing, or RNA stability. The TREX complex assembled on every mRNA examined. Mutation analysis showed that the C terminus of ALY was required for binding of both UAP56 and the THO complex. The C terminus of UAP56 was sufficient for ALY binding. The N terminus of UAP56 interacted weakly with the THO complex and TEX1, suggesting that other regions of UAP56 are required for maximal binding. Masuda et al. (2005) concluded that recruitment of the human TREX complex is not directly coupled to transcription, as in yeast.
Hartz (2011) mapped the THOC7 gene to chromosome 3p14.1 based on an alignment of the THOC7 sequence (GenBank AK027098) with the genomic sequence (GRCh37).
Hartz, P. A. Personal Communication. Baltimore, Md. 11/2/2011.
Masuda, S., Das, R., Cheng, H., Hurt, E., Dorman, N., Reed, R. Recruitment of the human TREX complex to mRNA during splicing. Genes Dev. 19: 1512-1517, 2005. [PubMed: 15998806] [Full Text: https://doi.org/10.1101/gad.1302205]
Tascou, S., Kang, T. W., Trappe, R., Engel, W., Burfeind, P. Identification and characterization of NIF3L1 BP1, a novel cytoplasmic interaction partner of the NIF3L1 protein. Biochem. Biophys. Res. Commun. 309: 440-448, 2003. [PubMed: 12951069] [Full Text: https://doi.org/10.1016/j.bbrc.2003.07.008]