MPI Colloquia Series: Prof. Dr. Kay Hofmann, University of Cologne: Here be clippases! Hunting for treasures in uncharted deubiquitinase territory

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Here be clippases! Hunting for treasures in uncharted deubiquitinase territory

In eukaryotes, protein ubiquitination regulates virtually every cellular pathway, including the defense against bacterial pathogens. Several bacteria secrete deubiquitinase (DUB) effectors into the host cell, which help them to evade ubiquitin-based lysosomal targeting. Typical intracellular bacteria encode one or two DUBs, usually targeting K63-linked chains or lacking linkage specificity. So far, Legionella pneumophila is the only known bacterium with a massively expanded and diversified ubiquitin-effector repertoire. We set up a bioinformatical screen to systematically search for novel deubiquitinases in bacterial genomes - focussing on criteria that discriminate between DUBs and cysteine proteases of other specificities. Interestingly, when studying DUBs of poorly-characterized bacteria associated with various non-mammalian hosts, a number of unusual enzymes was discovered, which shed light on the factors shaping bacterial effector repertoires, and can also be used as tools for studying the human ubiquitin system.