The caspase Dronc functions in both living and dying cells.

<p>The <i>Drosophila</i> caspase Dronc, which is required for fly development, is composed of an N-terminal CARD domain, a large subunit (L) containing the Cys active site required for proteolytic catalysis, and a small subunit (S) that is auto-catalytically cleaved from the precursor zymogen following recruitment to the Dark apoptosome. The ubiquitin ligase Diap1 mono-ubiquitylates lysine 78 in the CARD domain, which inhibits cell death by interfering with formation of the Dronc–Dark apoptosome. In contrast to non-apoptotic functions of Dronc in some model systems, Dronc’s proteolytic activity is unexpectedly not required for Dronc’s role in apoptosis-induced cell proliferation. Surprisingly, mono-ubiquitylation also suppresses this non-apoptotic function of Dronc, as Dark is still required. Thus, an alternative CARD-independent interaction with Dark or other factor could potentially mediate the observed non-death functions of Dronc.