title: Exposure of bipartite hydrophobic signal triggers nuclear quality control of Ndc10 at the endoplasmic reticulum/nuclear envelope.
abstract: Proper functioning of the protein-folding quality control network depends on the network's ability to discern diverse structural perturbations to the native states of its protein substrates. Despite the centrality of the detection of misfolded states to cell home-ostasis, very little is known about the exact sequence and structural features that mark a protein as being misfolded. To investigate these features, we studied the requirements for the degradation of the yeast kinetochore protein Ndc10p. Mutant Ndc10p is a substrate of a protein-folding quality control pathway mediated by the E3 ubiquitin (Ub) ligase Doa10p at the endoplasmic reticulum (ER)/nuclear envelope membrane. Analysis of Ndc10p mutant derivatives, employing a reverse genetics approach, identified an autonomous quality control-associated degradation motif near the C-terminus of the protein. This motif is composed of two indispensable hydrophobic elements: a hydrophobic surface of an amphipathic helix and a loosely structured hydrophobic C-terminal tail. Site-specific point mutations expose these elements, triggering ubiquitin-mediated and HSP70 chaperone-dependent degradation of Ndc10p. These findings substantiate the ability of the ER quality control system to recognize subtle perturbation(s) in the native structure of a nuclear protein.
authors: Department of Biological Chemistry, A Silberman Institute of Life Sciences, Jerusalem 91904, Israel.
authors: Noa
authors: N
authors: Furth
authors: Or
authors: O
authors: Gertman
authors: Ayala
authors: A
authors: Shiber
authors: Omri S
authors: OS
authors: Alfassy
authors: Itamar
authors: I
authors: Cohen
authors: Masha M
authors: MM
authors: Rosenberg
authors: Nurit Kleinberger
authors: NK
authors: Doron
authors: Assaf
authors: A
authors: Friedler
authors: Tommer
authors: T
authors: Ravid
mesh_terms: D020816:Amino Acid Motifs; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D057927:Hydrophobic and Hydrophilic Interactions; D018386:Kinetochores / Q000378:metabolism*; D009154:Mutation; D009685:Nuclear Envelope / Q000235:genetics / Q000378:metabolism*; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D059748:Proteolysis; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism
chemical_list: C081071:CBF2 protein, S cerevisiae; D004268:DNA-Binding Proteins; D018840:HSP70 Heat-Shock Proteins; C090869:SSA3 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C091362:SSM4 protein, S cerevisiae; D044767:Ubiquitin-Protein Ligases