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Volume 4 Issue 5, May 2002

Recruitment of an engineered tagged Ras effector (orange) to the Golgi and the plasma membrane after activation of Ras by epidermal growth factor.

Volume 4 Issue 5

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Brief Communication

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Erratum

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Editorial

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Commentary

  • The proteasome is a hollow cylindrical protease that contains active sites concealed within its central cavity. Proteasomes usually completely degrade substrates into small peptides, but in a few cases, degradation can yield biologically active protein fragments. Examples of this are the transcription factors NF-κB, Spt23p and Mga2p, which are generated from precursors by proteasomal processing. How distinct protein domains are spared from degradation remains a matter of debate. Here, we discuss several models and suggest a novel mechanism for proteasomal processing.

    • Michael Rape
    • Stefan Jentsch
    Commentary
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News & Views

  • The Par-1/MARK kinases have a conserved role in cell polarization and are required to establish the anterior–posterior axis of Caenorhabditis elegans and Drosophila melanogaster. Now, elegant studies in Drosophila uncover the posterior patterning molecule Oskar (Osk) as a direct target of Par-1. Phosphorylation of Oskar at the posterior pole stabilizes the protein and contributes to its localized accumulation at high levels.

    • Simon L. Bullock
    • David Ish-Horowicz
    News & Views

  • The anaphase-promoting complex (APC) initiates exit from mitosis by ubiquitinating A- and B-type cyclins, the activating subunits of cyclin-dependent kinase 1 (Cdk1). Subsequently, the APC has to be inactivated to allow the re-accumulation of mitotic cyclins in the next cell cycle. A newly identified inhibitor of the APC, called Emi1 in vertebrates and Rca1 in Drosophila melanogaster, may have an important function in inactivating the APC during interphase.

    • Hartmut C. Vodermaier
    • Jan-Michael Peters
    News & Views

  • Polyubiquitin chains are assembled onto proteins destined for degradation. The target protein is then unfolded by the proteasome and translocated through a channel leading from the unfolding site to an internal chamber of the enzyme for hydrolysis. A recent paper illuminates the long-elusive polyubiquitin chain recognition step that initiates this sequence of events at the proteasome.

    • Daniel Finley
    News & Views
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