Gpn1 and Gpn3 associate tightly and their protein levels are mutually dependent in mammalian cells

Gpn1 and Gpn3 are GTPases individually required for nuclear targeting of RNA polymerase II. Here we show that whereas Gpn3-EYFP distributed between the cytoplasm and cell nucleus, it was mainly cytoplasmic when coexpressed with Gpn1-Flag. Gpn3-Flag retained Gpn1-EYFP in the cytoplasm. However, Gpn3-EYFP/Gpn1-Flag nucleocytoplasmic shuttling was revealed after inhibiting nuclear export with leptomycin B. All Gpn3-EYFP coimmunoprecipitated with Gpn1-Flag, and all Gpn1-EYFP with Gpn3-Flag. Importantly, most endogenous Gpn1 and Gpn3 also associate. Gpn1-Gpn3 interaction was essential to maintain steady-state protein levels of both GTPases. We propose that most Gpn1 and Gpn3 associate, are mobilized, and function as a protein complex. © 2014 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Gpn1; Gpn1-Gpn3 interaction; Gpn1-Gpn3 nucleocytoplasmic shuttling; Gpn3; Interdependent protein levels; shRNA guanosine triphosphatase; leptomycin B; protein Gpn1; protein Gpn3; unclassified drug; GPN1 protein, human; guanine nucleotide binding protein; guanosine triphosphatase; Parcs protein, human; protein binding; Article; cell nucleus; controlled study; cytoplasm; human; human cell; immunoprecipitation; in vivo study; mammal cell; nuclear export signal; nucleocytoplasmic transport; protein expression; protein function; protein localization; protein protein interaction; steady state; active transport; animal; metabolism; tumor cell line; Active Transport, Cell Nucleus; Animals; Cell Line, Tumor; Cell Nucleus; Cytoplasm; GTP Phosphohydrolases; GTP-Binding Proteins; Humans; Protein Binding

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