The Nuclear Ins and Outs of tRNA

Science  01 Jul 2005:
Vol. 309, Issue 5731, pp. 15h
DOI: 10.1126/science.309.5731.15h

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. (p. 140, published online 19 May 2005) 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 upon 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.

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