The Mechanism of Ran Import into the Nucleus by Nuclear Transport Factor 2

• Type of Material: Article
• Authors: B. Booth Quimby, Emory University; Todd Lamitina, Emory University; Steven L'Hernault, Emory University; Anita Corbett, Emory University
• Language: English
• Date: 2000-09-01
• Publisher: Elsevier
• Publication Version: Final Published Version
• Copyright Statement: © 2000 ASBMB. Currently published by Elsevier Inc; originally published by American Society for Biochemistry and Molecular Biology.
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): https://doi.org/10.1074/jbc.M005055200
• Title of Journal or Parent Work: Journal of Biological Chemistry
• Volume: 275
• Issue: 37
• Start Page: 28575
• End Page: 28582
• Grant/Funding Information: Supported by U.S. Public Health Service Grant GMRO1GM40697 and National Science Foundation Grant IBN-9631102.; Biochemistry, Cell, and Molecular Biology Predoctoral Training Grant 5T32GM08367.; National Institutes of Health Fellowship 5F32GM19681.; The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
• Keywords: guanosine 5′-3-O-(thio)triphosphate; nuclear transport factor; GTPase activating protein; guanyl-5′-yl thiophosphate; nuclear localization signal; double-stranded RNA; guanine nucleotide exchange factor; bovine serum albumin; polyacrylamide gel electrophoresis; nuclear pore complex; phenylmethylsulfonylfluoride; green fluorescent protein
• Research Categories: Biology, Genetics; Biology, Cell

Abstract

The small GTPase Ran is essential for virtually all nucleocytoplasmic transport events. It is hypothesized that Ran drives vectorial transport of macromolecules into and out of the nucleus via the establishment of a Ran gradient between the cytoplasm and nucleoplasm. Although Ran shuttles between the nucleus and cytoplasm, it is concentrated in the nucleus at steady state. We show that nuclear transport factor 2 (NTF2) is required to concentrate Ran in the nucleus in the budding yeast, Saccharomyces cerevisiae. To analyze the mechanism of Ran import into the nucleus by NTF2, we use mutants in a variety of nuclear transport factors along with biochemical analyses of NTF2 complexes. We find that Ran remains concentrated in the nucleus when importin-mediated protein import is disrupted and demonstrate that NTF2 does not form a stable complex with the transport receptor, importin-β. Consistent with a critical role for NTF2 in establishing and maintaining the Ran gradient, we show that NTF2 is required for early embryogenesis inCaenorhabditis elegans. Our data distinguish between two possible mechanisms for Ran import by NTF2 and demonstrate that Ran import is independent from importin-β-mediated protein import.