First published online November 23, 2005
Journal of Cell Science 118, 2302e (2005)
© The Company of Biologists Limited
The tracks of my TIARs
Movement of proteins into and out of the nucleus is usually driven by the small GTPase Ran and mediated by transport receptors of the karyopherin (importin/exportin) family. Studies by Veronique Kruys and co-workers now reveal that two RNA-binding proteins, TIAR and TIA-1, use a different mechanism (see p. 5453). TIAR and TIA-1 regulate several aspects of RNA metabolism, including splicing and translation. Kruys and co-workers show that they shuttle into and out of the nucleus but lack the classical nuclear localization/export sequences that bind to karyopherins. Instead, the authors find that nuclear import and export depend on the presence of functional RNA-recognition motifs (RMMs) in the proteins (RMM2 and RMM3, respectively). They also demonstrate that RMM3 can drive export of a heterologous protein normally confined to the nucleus. Kruys and co-workers go on to show that export - but not import - of TIAR and TIA-1 is independent of Ran. Their findings thus establish the existence of a novel karyopherin-independent shuttling mechanism in which TIAR/TIA-1 may hitch a ride on RNA. In addition, they provide the first evidence for different functions of the RMMs in these RNA-binding proteins.
Related articles in JCS:
- Identification of the sequence determinants mediating the nucleo-cytoplasmic shuttling of TIAR and TIA-1 RNA-binding proteins
- Tong Zhang, Nathalie Delestienne, Georges Huez, Véronique Kruys, and Cyril Gueydan
JCS 2005 118: 5453-5463.
[Abstract]
[Full Text]
