The linear ubiquitin chain assembly complex (LUBAC) is the only known ubiquitin ligase for linear/Met1-linked ubiquitin chain formation. One of the LUBAC components, HOIL-1L, was recently shown to catalyse oxyester bond formation between ubiquitin and some substrates. However, oxyester bond formation in the context of LUBAC has not been directly observed. Here, we present the first 3D reconstruction of human LUBAC obtained by electron microscopy and report its generation of heterotypic ubiquitin chains containing linear linkages with oxyester-linked branches. We found that this event depends on HOIL-1L catalytic activity. By cross-linking mass spectrometry showing proximity between the catalytic RBR domains, a coordinated ubiquitin relay mechanism between the HOIP and HOIL-1L ligases is suggested. In mouse embryonic fibroblasts, these heterotypic chains were induced by TNF, which is reduced in cells expressing an HOIL-1L catalytic inactive mutant. In conclusion, we demonstrate that LUBAC assembles heterotypic ubiquitin chains by the concerted action of HOIP and HOIL-1L.
The linear ubiquitin chain assembly complex (LUBAC) is the only known ubiquitin ligase that generates linear/Met1-linked ubiquitin chains. One of the LUBAC components, HOIL-1L, was recently shown to catalyse oxyester bond formation between the C-terminus of ubiquitin and some substrates. However, oxyester bond formation by LUBAC has not been directly observed. We present the first low-resolution 3D structure of LUBAC obtained by electron microscopy and report its generation of heterotypic ubiquitin chains containing linear linkages with oxyester-linked branches. We found that addition of the oxyester-bound branches depends on HOIL-1L catalytic activity. We suggest a coordinated ubiquitin relay mechanism between the two ligases supported by cross-linking mass spectrometry data, which show proximity between the catalytic RBR domains of HOIP and HOIL-1L, Mutations in the linear ubiquitin chain-binding NZF domain of HOIL-1L reduces chain branching suggesting its role in the process. In cells, these heterotypic chains were induced by TNF. In conclusion, we demonstrate that LUBAC assembles heterotypic ubiquitin chains with linear and oxyester-linked branches by the concerted action of HOIP and HOIL-1L.Keywords: E3 ubiquitin ligase/ Ester-bond linkage/ HOIL-1L/ RBR/ Ubiquitin
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.