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The K nuclear shuttling domain: a novel signal for nuclear import and nuclear export in the hnRNP K protein
Author(s) -
Michael W.Matthew,
Eder Paul S.,
Dreyfuss Gideon
Publication year - 1997
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/16.12.3587
Subject(s) - nuclear transport , nuclear export signal , nuclear localization sequence , nls , heterogeneous nuclear ribonucleoprotein , heterogeneous ribonucleoprotein particle , biology , microbiology and biotechnology , ribonucleoprotein , nuclear protein , nucleoporin , nuclear pore , importin , nucleus , cell nucleus , transcription factor , rna , genetics , gene
Protein import into the nucleus and export from the nucleus are signal‐mediated processes that require energy. The nuclear transport process about which the most information is currently available is classical nuclear localization signal (NLS)‐mediated nuclear import. However, details concerning the signal‐mediated export of proteins and RNAs as well as alternative nuclear import pathways are beginning to emerge. An example of this is the heterogeneous nuclear ribonucleoprotein (hnRNP) A1 protein which, by virtue of its M9 domain, is actively exported from the nucleus and imported into the nucleus via a novel pathway mediated by the recently characterized transportin protein. Here we report that the shuttling hnRNP K protein contains a novel shuttling domain (termed KNS) which has many of the characteristics of M9, in that it confers bi‐directional transport across the nuclear envelope. KNS‐mediated nuclear import is dependent on RNA polymerase II transcription, and we show that a classical NLS can override this effect. Furthermore, KNS accesses a separate import pathway from either classical NLSs or M9. This demonstrates the existence of a third protein import pathway into the nucleus and thereby defines a new type of nuclear import/export signal.