Many nuclear proteins are imported into the cell nucleus by the "classical" nuclear localization signal (NLS)-mediated import pathway. In this pathway, a sequence rich in basic residues in the protein interacts with a heterodimeric complex termed importin and this, along with the GTPase Ran, mediates nuclear import of the NLS-bearing protein. The heterogeneous nuclear ribonucleoprotein (hnRNP) A1 protein contains a novel nuclear localization sequence, termed M9, that does not contain any clusters of basic residues. Very recently, we showed that M9 directs import into the nucleus by a novel protein import pathway distinct from the classical NLS pathway. A 90-kilodalton protein termed transportin was identified as a protein that specifically interacts with wild-type M9 but not transport-defective M9 mutants. Transportin and an ATP-regenerating system were found to be necessary and sufficient for import of M9-containing proteins in an in vitro import assay. In this report, we provide additional evidence that transportin can interact directly with M9-containing proteins and also show that it can mediate import of full-length hnRNP A1. In addition, Ran, or a Ran-binding protein, is identified as a second protein component of this novel nuclear import pathway. Transportin relatives from Saccharomyces cerevisiae which likely serve as additional nuclear transport receptors are described.
|Evidence ID||Analyze ID||Interactor||Interactor Systematic Name||Interactor||Interactor Systematic Name||Type||Assay||Annotation||Action||Modification||Phenotype||Source||Reference||Note|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Gene Ontology Term||Gene Ontology Term ID||Qualifier||Aspect||Method||Evidence||Source||Assigned On||Reference||Annotation Extension|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Phenotype||Experiment Type||Experiment Type Category||Mutant Information||Strain Background||Chemical||Details||Reference|
|Evidence ID||Analyze ID||Regulator||Regulator Systematic Name||Target||Target Systematic Name||Experiment||Conditions||Strain||Source||Reference|