The linear ubiquitin chain assembly complex (LUBAC) generates heterotypic ubiquitin chains

Elife. 2021 Jun 18;10:e60660. doi: 10.7554/eLife.60660.

Abstract

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, heme-oxidized IRP2 ubiquitin ligase 1 (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 RING-in-between-RING (RBR) domains, a coordinated ubiquitin relay mechanism between the HOIL-1-interacting protein (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.

Keywords: E3 ubiquitin ligase; HOIL-1L; RBR; biochemistry; chemical biology; mouse; oxyester-bond linkage; ubiquitin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Carrier Proteins / metabolism
  • Cells, Cultured
  • Female
  • Fibroblasts / metabolism
  • Humans
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Protein Domains
  • Transcription Factors* / chemistry
  • Transcription Factors* / genetics
  • Transcription Factors* / metabolism
  • Ubiquitin* / chemistry
  • Ubiquitin* / metabolism
  • Ubiquitin-Protein Ligases* / chemistry
  • Ubiquitin-Protein Ligases* / genetics
  • Ubiquitin-Protein Ligases* / metabolism

Substances

  • Carrier Proteins
  • HOIL-1L protein, mouse
  • Transcription Factors
  • Ubiquitin
  • RBCK1 protein, human
  • RNF31 protein, human
  • Ubiquitin-Protein Ligases

Grant support

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.