THOC2 Mutations Implicate mRNA-Export Pathway in X-Linked Intellectual Disability.
Kumar R
et al.
Am J Hum Genet 2015 Aug;97(2)302-310
Kumar R, Corbett MA, van Bon BW, Woenig JA, Weir L, Douglas E, Friend KL, Gardner A, Shaw M, Jolly LA, Tan C, Hunter MF, Hunter MF, Hackett A, Field M, Palmer EE, Leffler M, Rogers C, Boyle J, Bienek M, Jensen C, Van Buggenhout G, Van Esch H, Hoffmann K, Raynaud M, Zhao H, Reed R, Hu H, Haas SA, Haan E, Kalscheuer VM, Gecz J.
Am J Hum Genet 2015 Aug;97(2)302-310
Abstract: Export of mRNA from the cell nucleus to the cytoplasm is essential for protein synthesis, a process vital to all living eukaryotic cells. mRNA export is highly conserved and ubiquitous. Mutations affecting mRNA and mRNA processing or export factors, which cause aberrant retention of mRNAs in the nucleus, are thus emerging as contributors to an important class of human genetic disorders. Here, we report that variants in THOC2, which encodes a subunit of the highly conserved TREX mRNA-export complex, cause syndromic intellectual disability (ID). Affected individuals presented with variable degrees of ID and commonly observed features included speech delay, elevated BMI, short stature, seizure disorders, gait disturbance, and tremors. X chromosome exome sequencing revealed four missense variants in THOC2 in four families, including family MRX12, first ascertained in 1971. We show that two variants lead to decreased stability of THOC2 and its TREX-complex partners in cells derived from the affected individuals. Protein structural modeling showed that the altered amino acids are located in the RNA-binding domains of two complex THOC2 structures, potentially representing two different intermediate RNA-binding states of THOC2 during RNA transport. Our results show that disturbance of the canonical molecular pathway of mRNA export is compatible with life but results in altered neuronal development with other comorbidities.
Recruitment of the human TREX complex to mRNA during splicing.
Masuda S
et al.
Genes Dev 2005 Jul;19(13)1512-1517
Masuda S, Das R, Cheng H, Hurt E, Dorman N, Reed R.
Genes Dev 2005 Jul;19(13)1512-1517
Abstract: In yeast, the TREX complex contains the THO transcription elongation complex, which functions in direct cotranscriptional recruitment of the mRNA export proteins Sub2 and Yra1 to nascent transcripts. Here we report the identification of the human THO complex and show that it associates with spliced mRNA, but not with unspliced pre-mRNA in vitro. Transcription is not required for this recruitment. We also show that the human THO complex colocalizes with splicing factors in nuclear speckle domains in vivo. Considering that splicing occurs cotranscriptionally in humans, our data indicate that recruitment of the human TREX complex to spliced mRNA is not directly coupled to transcription, but is instead coupled to transcription indirectly through splicing.
TREX is a conserved complex coupling transcription with messenger RNA export.
Strässer K
et al.
Nature 2002 May;417(6886)304-308
Strässer K, Masuda S, Mason P, Pfannstiel J, Oppizzi M, Rodriguez-Navarro S, Rondón AG, Aguilera A, Struhl K, Reed R, Hurt E.
Nature 2002 May;417(6886)304-308
Abstract: The essential yeast proteins Yra1 and Sub2 are messenger RNA export factors that have conserved counterparts in metazoans, designated Aly and UAP56, respectively. These factors couple the machineries that function in splicing and export of mRNA. Here we show that both Yra1 and Sub2 are stoichiometrically associated with the heterotetrameric THO complex, which functions in transcription in yeast. We also show that Sub2 and Yra1 interact genetically with all four components of the THO complex (Tho2, Hpr1, Mft1 and Thp2). Moreover, these components operate in the export of bulk poly(A)(+) RNA as well as of mRNA derived from intronless genes. Both Aly and UAP56 associate with human counterparts of the THO complex. Together, these data define a conserved complex, designated the TREX ('transcription/export') complex. The TREX complex is specifically recruited to activated genes during transcription and travels the entire length of the gene with RNA polymerase II. Our data indicate that the TREX complex has a conserved role in coupling transcription to mRNA export.
