Proteolysis articles within Nature

Featured

  • Letter |

    The transcription cofactor CBF-β is shown to regulate the ability of HIV-1 to evade host restriction mediated by the deaminase APOBEC3; it acts by interacting with the HIV protein Vif, so disrupting the Vif–CBF-β interaction could provide a new therapeutic target against HIV-1 infection.

    • Stefanie Jäger
    • , Dong Young Kim
    •  & Nevan J. Krogan

  • Letter |

    Genome-wide analysis shows that H2B S112 O-linked to N-acetylglucosamine is frequently located near transcribed genes, suggesting that histone GlcNAcylation facilitates transcription of the genes.

    • Ryoji Fujiki
    • , Waka Hashiba
    •  & Shigeaki Kato

  • Letter |

    The ubiquitin conjugation system regulates the canonical NF-κB activation pathway, which mediates immune responses. Linear polyubiquitin chains—in which the C terminal glycine of ubiquitin is conjugated to the α-amino group of the amino-terminal methionine of another ubiquitin—are generated by a unique ubiquitin ligase complex called linear ubiquitin chain assembly complex (LUBAC) composed of two RING domain proteins called HOIL-1 and HOIP. This is one of three complementary studies identifying a novel component of the LUBAC complex called SHARPIN, which is recruited to receptor signalling complexes (RSCs) that form after TNF and CD40L stimulation. The LUBAC complex containing SHARPIN stimulates the formation of linear ubiquitin chains in vitro and in vivo and is required for the activation of NF-κB signalling.

    • Fumiyo Ikeda
    • , Yonathan Lissanu Deribe
    •  & Ivan Dikic

  • Article |

    Regulated proteolysis by ATP-dependent proteases have a crucial role in protein quality control in cells. The Clp/Hsp100 proteins of the AAA+ superfamily of ATP-dependent chaperones unfold and translocate proteins into the proteolytic chamber of protease complexes. ClpC requires the adaptor protein MecA for activation and substrate targetting to the ClpCP protease complex. Here, a structural and biochemical analysis is presented of the MecA–ClpC complex revealing organizational principles and providing mechanistic insights into this complex molecular machine.

    • Feng Wang
    • , Ziqing Mei
    •  & Yigong Shi

  • News & Views |

    Solving the structure of protein complexes is particularly challenging when they contain many subunits. In the case of the APC, a fruitful strategy has been to gain information by subtracting subunits. See Article p.227 and Letter p.274

    • Ian Foe
    •  & David Toczyski

  • Letter |

    The anaphase promoting complex/cyclosome (APC/C) is a large multimeric ubiquitin E3 ligase that regulates the eukaryotic cell cycle in processes such as chromatid segregation and completion of mitosis. It catalyses the polyubiquitylation of a diverse array of mitotic regulatory proteins and targets them for proteasomal degradation. Target selection also involves a co-activator protein (either Cdc20 or Cdh1) together with core APC/C subunits. Here, a cryo-EM structure of APC/CChd1 bound to a D-box peptide substrate is presented. The structure provides important insight into the recognition and catalytic mechanism of APC/C substrates.

    • Paula C. A. da Fonseca
    • , Eric H. Kong
    •  & David Barford

  • Letter |

    The proteasome is a multi-protein complex that enzymatically degrades proteins. Proteolysis occurs in a barrel-shaped 20S core particle comprising three interconnected cavities, including a pair of antechambers in which substrates are held before degradation. These authors demonstrate that substrates interact actively with the antechamber walls and that the environment in this compartment is optimized to maintain the substrates in unfolded states so as to be accessible for hydrolysis.

    • Amy M. Ruschak
    • , Tomasz L. Religa
    •  & Lewis E. Kay

  • Letter |

    The translation of messenger RNA that lacks stop codons results in the production of aberrant proteins, which may have harmful effects on the cell. It is unclear how eukaryotic cells eliminate these 'non-stop' proteins. Here it is shown that, in Saccharomyces cerevisiae, an E3 ubiquitin ligase called Ltn1 acts in the quality-control pathway. It associates with ribosomes and marks non-stop proteins with ubiquitin, which targets the proteins for degradation.

    • Mario H. Bengtson
    •  & Claudio A. P. Joazeiro

  • Article |

    In the ubiquitin–proteasome system, substrates destined for destruction are modified with ubiquitin chains and then degraded by the proteasome. These authors reveal a regulatory mechanism in which proteasomal activity is modulated by the length of ubiquitin chains in human cells. They find that deubiquitinating enzyme USP14 can inhibit the degradation of ubiquitin-conjugated substrates by trimming ubiquitin chains, and that stimulation of proteasome activity may be used to reduce the levels of toxic proteins in cells.

    • Byung-Hoon Lee
    • , Min Jae Lee
    •  & Daniel Finley

  • Article |

    Although Archaea encode proteasomes highly related to those of eukaryotes, archaeal ubiquitin-like proteins are less conserved and not known to function in protein conjugation, complicating our understanding of the origins of ubiquitination. Two small archaeal modifier proteins, SAMP1 and SAMP2, structurally similar to ubiquitin, are now reported to form protein conjugates in the archaeon Haloferax volcanii.

    • Matthew A. Humbard
    • , Hugo V. Miranda
    •  & Julie A. Maupin-Furlow

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