The Nuclear Ins and Outs of tRNA

Science's STKE  05 Jul 2005:
Vol. 2005, Issue 291, pp. tw247
DOI: 10.1126/stke.2912005tw247

Transfer RNA (tRNA) is part of the machinery that converts the nucleic acid genetic code into protein. In the nucleus, tRNAs are transcribed, trimmed, and modified and, after being checked by an intranuclear quality-control system, are exported to the cytosol, ready to promote protein translation. Takano et al. now find that mature cytosolic tRNAs are actively transported back into the nucleus by a mechanism that is independent of the usual nuclear protein import machinery that relies on the small guanosine triphosphatase Ran. It is not clear why tRNA needs to return to the nucleus--perhaps to be subjected to further quality control or perhaps even to promote hypothetical nuclear translation.

A. Takano, T. Endo, T. Yoshihisa, tRNA actively shuttles between the nucleus and cytosol in yeast. Science 309, 140-142 (2005). [Abstract] [Full Text]