Antagonistic effects of NES and NLS motifs determine S. cerevisiae Rna1p subcellular distribution.
Nucleus/cytosol exchange requires a GTPase, Ran. In yeast Rna1p is the GTPase activating protein for Ran (RanGAP) and Prp20p is the Ran GDP/GTP exchange factor (GEF). RanGAP is primarily cytosolic and GEF is nuclear. Their subcellular distributions led to the prediction that Ran-GTP hydrolysis takes place solely in the cytosol and GDP/GTP exchange solely in the nucleus. Current models propose that the Ran-GTP/Ran-GDP gradient across the nuclear membrane determines the direction of exchange. We provide three lines of evidence that Rna1p enters and leaves the nuclear interior. (1) Rna1p possesses leucine-rich nuclear export sequences (NES) that are able to relocate a passenger karyophilic protein to the cytosol; alterations of consensus residues re-establish nuclear location. (2) Rna1p possesses other sequences that function as a novel nuclear localization sequence able to deliver a passenger cytosolic protein to the nucleus. (3) Endogenous Rna1p location is dependent upon Xpo1p/Crm1p, the yeast exportin for leucine-rich NES-containing proteins. The data support the hypothesis that Rna1p exists on both sides of the nuclear membrane, perhaps regulating the Ran-GTP/Ran-GDP gradient, participating in a complete RanGTPase nuclear cycle or serving a novel function.
Feng
W
W
Department of Biochemistry and Molecular Biology, Pennsylvania State University College of Medicine, Hershey, PA 17033, USA.
Benko
A L
AL
Lee
J H
JH
Stanford
D R
DR
Hopper
A K
AK
D000595:Amino Acid Sequence; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D020558:GTP Phosphohydrolases / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000032:analysis* / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D020690:GTPase-Activating Proteins; D008969:Molecular Sequence Data; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins / Q000378:metabolism / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D016415:Sequence Alignment; D020931:ran GTP-Binding Protein
D020690:GTPase-Activating Proteins; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; C060997:RNA1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D020931:ran GTP-Binding Protein