Retrograde tRNAs

Mature tRNAs move between the cytoplasm and the nucleus in S. cerevisiae, report Akira Takano, Toshiya Endo, and Tohru Yoshihisa (Nagoya University, Japan), and Hussam Shaheen and Anita Hopper (Pennsylvania State University College of Medicine, Hershey, PA) in two independent reports.

“The dogma was that tRNAs are transcribed in the nucleus and function in the cytoplasm, and that is the whole story,” says Hopper. “But the whole tRNA model has become much more complex, and almost anything one would have thought would be true has turned out to be wrong.”Previous work showed that, when yeast were starved, tRNAs lacking introns were more abundant in the nucleus. It was not clear though whether they were processed in the nucleus and held there, or whether they underwent retrograde transport and returned to the nucleus...