title: Sequential Poly-ubiquitylation by Specialized Conjugating Enzymes Expands the Versatility of a Quality Control Ubiquitin Ligase.
abstract: The Doa10 quality control ubiquitin (Ub) ligase labels proteins with uniform lysine 48-linked poly-Ub (K48-pUB) chains for proteasomal degradation. Processing of Doa10 substrates requires the activity of two Ub conjugating enzymes. Here we show that the non-canonical conjugating enzyme Ubc6 attaches single Ub molecules not only to lysines but also to hydroxylated amino acids. These Ub moieties serve as primers for subsequent poly-ubiquitylation by Ubc7. We propose that the evolutionary conserved propensity of Ubc6 to mount Ub on diverse amino acids augments the number of ubiquitylation sites within a substrate and thereby increases the target range of Doa10. Our work provides new insights on how the consecutive activity of two specialized conjugating enzymes facilitates the attachment of poly-Ub to very heterogeneous client molecules. Such stepwise ubiquitylation reactions most likely represent a more general cellular phenomenon that extends the versatility yet sustains the specificity of the Ub conjugation system.
authors: Intracellular Proteolysis, Max-Delbrueck-Center for Molecular Medicine, 13125 Berlin, Germany.
authors: Annika
authors: A
authors: Weber
authors: Department of Biological Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel.
authors: Itamar
authors: I
authors: Cohen
authors: Mass Spectrometric Core Facility, Max-Delbrueck-Center for Molecular Medicine, 13125 Berlin, Germany.
authors: Oliver
authors: O
authors: Popp
authors: Mass Spectrometric Core Facility, Max-Delbrueck-Center for Molecular Medicine, 13125 Berlin, Germany.
authors: Gunnar
authors: G
authors: Dittmar
authors: Department of Biological Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel.
authors: Yuval
authors: Y
authors: Reiss
authors: Intracellular Proteolysis, Max-Delbrueck-Center for Molecular Medicine, 13125 Berlin, Germany; Institute of Biology, Humboldt University Berlin, 10099 Berlin, Germany. Electronic address: tsommer@mdc-berlin.de.
authors: Thomas
authors: T
authors: Sommer
authors: Department of Biological Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel. Electronic address: tommer.ravid@mail.huji.ac.il.
authors: Tommer
authors: T
authors: Ravid
authors: Intracellular Proteolysis, Max-Delbrueck-Center for Molecular Medicine, 13125 Berlin, Germany. Electronic address: ejarosch@mdc-berlin.de.
authors: Ernst
authors: E
authors: Jarosch
mesh_terms: D000595:Amino Acid Sequence; D015966:Gene Expression Regulation, Fungal; D006801:Humans; D006900:Hydroxylation; D008239:Lysine / Q000378:metabolism; D025821:Polyubiquitin / Q000235:genetics / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D059748:Proteolysis; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013379:Substrate Specificity; D044763:Ubiquitin-Conjugating Enzymes / Q000235:genetics / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination
chemical_list: D029701:Saccharomyces cerevisiae Proteins; D025821:Polyubiquitin; C082461:UBC6 protein, S cerevisiae; C077072:UBC7 protein, S cerevisiae; D044763:Ubiquitin-Conjugating Enzymes; C091362:SSM4 protein, S cerevisiae; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex; D008239:Lysine