Transport into and out of the cell nucleus

Open Access
Publisher Website
Google Scholar
Abstract
Import, for example into mitochondria, chloroplasts or the rER, requires specific targeting sequences that are usually removed during import (for review see Rapoport et al., 1996; Schatz and Dobberstein, 1996). Once a protein has been imported, for example, into the rER, there is normally no return to the cytoplasm. In contrast, in the case of nuclear transport, import and export are equally major processes (for review see Görlich, 1997; Nigg, 1997; Mattaj and Englmeier, 1998). Many proteins need to be imported into the nucleus multiple times, as is the case for proteins which shuttle continuously between nucleus and cytoplasm. In addition, higher eukaryotes have an open mitosis and all not‐chromatin‐bound nuclear proteins need to be re‐imported upon reformation of the nuclear envelope after mitosis. This may be a reason why nuclear import signals are not removed during import.