title: Nuclear localization signal peptides induce molecular delivery along microtubules.
abstract: Many essential processes in eukaryotic cells depend on regulated molecular exchange between its two major compartments, the cytoplasm and the nucleus. In general, nuclear import of macromolecular complexes is dependent on specific peptide signals and their recognition by receptors that mediate translocation through the nuclear pores. Here we address the question of how protein products bearing such nuclear localization signals arrive at the nuclear membrane before import, i.e., by simple diffusion or perhaps with assistance of cytoskeletal elements or cytoskeleton-associated motor proteins. Using direct single-particle tracking and detailed statistical analysis, we show that the presence of nuclear localization signals invokes active transport along microtubules in a cell-free Xenopus egg extract. Chemical and antibody inhibition of minus-end directed cytoplasmic dynein blocks this active movement. In the intact cell, where microtubules project radially from the centrosome, such an interaction would effectively deliver nuclear-targeted cargo to the nuclear envelope in preparation for import.
authors.affiliation: Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Hanna
authors.initials: H
authors.lastname: Salman
authors.forename: Asmahan
authors.initials: A
authors.lastname: Abu-Arish
authors.forename: Shachar
authors.initials: S
authors.lastname: Oliel
authors.forename: Avraham
authors.initials: A
authors.lastname: Loyter
authors.forename: Joseph
authors.initials: J
authors.lastname: Klafter
authors.forename: Rony
authors.initials: R
authors.lastname: Granek
authors.forename: Michael
authors.initials: M
authors.lastname: Elbaum
mesh_terms: D000199:Actins / Q000737:chemistry; D021581:Active Transport, Cell Nucleus; D000818:Animals; D001369:Axons / Q000378:metabolism; D001692:Biological Transport; D015153:Blotting, Western; D002467:Cell Nucleus / Q000378:metabolism*; D002474:Cell-Free System; D018385:Centrosome / Q000648:ultrastructure; D003593:Cytoplasm / Q000378:metabolism; D003599:Cytoskeleton / Q000737:chemistry / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000737:chemistry; D004058:Diffusion; D004398:Dyneins / Q000737:chemistry; D005260:Female; D015151:Immunoblotting; D028884:Karyopherins / Q000737:chemistry; D016547:Kinesins / Q000737:chemistry; D018613:Microscopy, Confocal; D008870:Microtubules / Q000378:metabolism / Q000648:ultrastructure*; D009154:Mutation; D019913:Nuclear Localization Signals / Q000737:chemistry*; D021382:Protein Sorting Signals; D013997:Time Factors; D014982:Xenopus laevis; D028961:beta Karyopherins / Q000737:chemistry
chemical_list: D000199:Actins; D004277:DNA, Single-Stranded; D028884:Karyopherins; D019913:Nuclear Localization Signals; D021382:Protein Sorting Signals; D028961:beta Karyopherins; D004398:Dyneins; D016547:Kinesins