The nuclear envelope is a membrane system which surrounds the nucleoplasm of eukaryotic cells. It is composed of the nuclear lamina, nuclear pore complexes and two nuclear membranes. The space between the two membranes is called the nuclear intermembrane space.
Importin, which transports target proteins into the nucleus. Specifically mediates the nuclear import of splicing factor serine/arginine (SR) proteins, such as RBM4, SFRS1 and SFRS2, by recognizing phosphorylated SR domains. Also mediates the nuclear import of serine/arginine (SR) protein CPSF6, independently of CPSF6 phosphorylation. The nuclear import process is regulated by the small GTPase Ran that partitions between cytoplasm and nucleus in the predominantly GDP- and GTP-bound form, respectively. Importin associates with target cargo proteins in the cytoplasm, and the competitive binding of GTP-bound Ran induces the release of cargos in the nucleus. {By
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National and Kapodistrian University of Athens
Department of Biology
Biophysics & Bioinformatics Laboratory