9.A.50 The Nuclear t-RNA Exporter (tRNA-E) Family tRNAs are made in the nucleolus of the nuclei of eukaryotes. They are processed and exported into the cytoplasm. The t-exporter consists of several proteins. The protein t-UTP8 acts between maturation and translocation across the nuclear pore complex. It interacts with the two tRNA export receptors, Los1 and Msn5, and the Ran GTPase, Gsp1 t-UTP8, probably transfers tRNA to the nuclear tRNA export receptors by using a channeling mechanism (Strub et al., 2007). Importins and exportins have been reviewed (Ding and Sepehrimanesh 2021; Azmi et al. 2021). These proteins are also tabulated under TC# 1.I.1.1.3 as part of the nuclear pore complex. Targeting deubiquitinase USP7-mediated stabilization of Exportin 6a (XPO6a) contributes to the anti-myeloma effects of selinexor (Wang et al. 2025). A role of XPO1 degradation in the anti-myeloma efficacy of SEL have been observed (Wang et al. 2025). T.he transport reaction catalyzes by a tRNA-exporter is: tRNA (nucleus) → tRNA (cytoplasm)
References:
Azmi, A.S., M.H. Uddin, and R.M. Mohammad. (2021). The nuclear export protein XPO1 - from biology to targeted therapy. Nat Rev Clin Oncol 18: 152-169.
Ding, B. and M. Sepehrimanesh. (2021). Nucleocytoplasmic Transport: Regulatory Mechanisms and the Implications in Neurodegeneration. Int J Mol Sci 22:.
Fung, H.Y.J., S.R. Mittal, A.B. Niesman, J. Jiou, B. Shakya, T. Yoshizawa, A.E. Cansizoglu, M.P. Rout, and Y.M. Chook. (2025). Phosphate-dependent nuclear export via a non-classical NES class recognized by exportin Msn5. Nat Commun 16: 2580.
Strub, B.R., M.B. Eswara, J.B. Pierce, and D. Mangroo. (2007). Utp8p is a nucleolar tRNA-binding protein that forms a complex with components of the nuclear tRNA export machinery in Saccharomyces cerevisiae. Mol. Biol. Cell 18: 3845-3859.
Wang, J., M. Chen, J. Jiang, Y. Wan, X. Li, M. Zhang, F. Xiao, L. Zhong, H. Zhong, Z. Qin, and J. Hou. (2025). Targeting deubiquitinase USP7-mediated stabilization of XPO1 contributes to the anti-myeloma effects of selinexor. J Transl Med 23: 62.
Examples:
TC#	Name	Organismal Type	Example
9.A.50.1.1	The tRNA nuclear export machinery, t-Exporter. Includes UTP8, a tRNA-binding protein, Los1 and Msn5/ two tRNA export receptors (Strub et al., 2007). Phosphate-dependent nuclear export via a non-classical NES class recognized by exportin Msn5 has been reported (Fung et al. 2025).	Yeast	tRNA Exporter of Saccharomyces cerevisiae: 1. t-UTP8 (P53276) 2. Exportin T (Los1; karyopherin-β) (P33418) 3. Msn5 (P52918) 4. GTP-binding nucleolus protein, GSP1/CNR1 (P32835)