EMBO J (2012) 31 19, 3833–3844 doi:; DOI: 10.1038/emboj.2012.217; published online September 07 2012
EMBO Rep (2012) 13 9, 840–846 doi:; DOI: 10.1038/embor.2012.105; published online September 07 2012
The ‘RING-between-RING’-type E3 ubiquitin ligase HOIP acts via a novel RING/HECT-hybrid ubiquitin transfer mechanism and catalyses the formation of linear ubiquitin chains by non-covalently binding the acceptor ubiquitin. But in the absence of a binding partner, HOIP is auto-inhibited. This explains why assembly of either HOIP/HOIL-1L or HOIP/SHARPIN is required to catalyse linear chain formation.