title: Location-specific depletion of a dual-localized protein.
abstract: In recent years, a growing number of proteins have been shown to be localized in more than one subcellular location, although encoded from a single gene. Fundamental aspects in the research of such dual-distributed proteins involve determination of their subcellular localization and their location-specific functions. The lack of sensitive and suitable tools to address these issues has led us to develop a novel tool for functional detection of cytosolic/nuclear isoproteins in the cell, which we term location-specific depletion or subcellular knockout. The depletion of the protein occurs post-translationally via degradation by the ubiquitin-proteasome system, which operates only in the cytosol and the nucleus. As an example, we fused the yeast tricarboxylic acid (TCA) cycle enzyme aconitase to a degron sequence (SL17) recognizable by the ubiquitin-proteasome system. This fusion resulted in the degradation of the cytosolic enzyme, specifically eliminating its activity within the cytosolic glyoxylate shunt without disrupting the protein's activity within the mitochondrial TCA cycle. We show that the degradation of the fusion protein can be attributed specifically to the ubiquitin-proteasome system and that inhibition of this degradation restores its cytosolic activity. This novel tool can be used to detect small subpopulations of dual-targeted proteins, thereby revealing isoproteins that were considered to be confined to a single compartment. The particular advantage of this specific subcellular depletion is that it can reveal the functions of the cytosolic/nuclear isoproteins.
authors.affiliation: Department of Molecular Biology, Hebrew University Medical School, Jerusalem 91120, Israel.
authors.forename: Lee
authors.initials: L
authors.lastname: Shlevin
authors.forename: Neta
authors.initials: N
authors.lastname: Regev-Rudzki
authors.forename: Sharon
authors.initials: S
authors.lastname: Karniely
authors.forename: Ophry
authors.initials: O
authors.lastname: Pines
mesh_terms: D000154:Aconitate Hydratase / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000201:enzymology / Q000378:metabolism; D003600:Cytosol / Q000201:enzymology / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D035941:Iron Regulatory Protein 1 / Q000378:metabolism; D007527:Isoenzymes; D008928:Mitochondria / Q000201:enzymology / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011487:Protein Conformation; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D014452:Ubiquitins / Q000378:metabolism
chemical_list: D007527:Isoenzymes; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D014452:Ubiquitins; D046988:Proteasome Endopeptidase Complex; D000154:Aconitate Hydratase; D035941:Iron Regulatory Protein 1